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INT-IDS Operation Manual

  1. Introduction
  2. Safety
  3. Troubleshooting
  4. Areas of the Telescope
  5. Preliminaries
  6. Filling the IDS Cryostat
  7. Zeroset and Pointing Calibration
  8. Switching the TCS Between Computer Mode and Engineering Mode
  9. Setting Up the Acquisition Camera
  10. Loading Catalogues
  11. Setting Up CCD and spectrograph parameters
  12. Neutral-density and order-sorting filters
  13. Preparing the Autoguider
  14. Sky Orientation in acquisition camera
  15. Calibration frames
  16. Opening Up
  17. Procedure for a 7-star and single star calibrate of telescope pointing
  18. Focusing the Telescope
  19. Target Acquisition
  20. Guiding
  21. Faint Target Acquisition
  22. Observing at Low Elevation (Altitude<33°)
  23. Observing Targets Moving at Non-Sidereal Rates
  24. Observing Commands
  25. Observing scripts
  26. Examining Data
  27. Closing Down at the End of the Night
  28. Closing Down in a Hurry
  29. Saving Data
  30. Creating the Night Log
  31. Filling in the Operations Logbook
  32. Leaving the Building
  33. Observers Handover Check
  34. Neutral-Density Filters for Calibrations
  35. Acknowledgements

1. Introduction

In this guide, the following syntax will be used:

  1. The system prompts will appear in the text as typewriter fonts, in the following format:
    USER>Commands to TCS (grey window on the Telescope Control System)
    SYS>Commands to ICS (pink window on the Instrument Control System)  
    ecl>IRAF commands on INTDRPC1
    DAS6@miranda>commads in the DAS screen of the Acquisition camera.
    $> Any other terminal window eg: xgterm
    Typewriter text indicates that the command exactly as it written in this page should be used. For variable input, curly braces will be used, e.g. {your_input}. Hence, in this web page it will be written:
      SYS> arc {time}
    to take an arc of {time} seconds exposure time. So, for taking an arc of 10 seconds, at the ICS prompt you should type:
      SYS> arc 10
  2. Words in green correspond to actual buttons to be pressed.

  3. Words as hyperlinks go to corresponding pictures or web pages with further details.

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2. Safety

  1. Before starting to work at the INT telescope it is essential that you carefully read the Safety Information. Please also print, read thoroughly and sign the page of Safety checklist for INT visiting astronomers. If you need more information ask your Support Astronomer (SA). To be able to work at INT, all the visitor astronomers that will be at INT for the run must agree to all the items by signing the page. After sign please hand the document to your SA. Note that ALL the observers that will be at the INT for the run should sign this page.

  2. You MUST always follow the instructions given to you by your SA or the WHT Telescope Operator (TO) (e.g. abandoning site in bad weather or regarding the operation of the telescope and instrument).

  3. Please use a lone worker alarm when you are alone at the INT. Your SA will explain you how it works on the first night of your run. It can be found on the back wall of the control room (see here). The lone worker alarm should never be taken away from INT building. In case of a real emergency, press simultaneously both orange buttons on the side (until you hear the beeping).

  4. Please do not use the elevator outside the Operations Team working hours (9:00-15:30 hrs) nor on weekends. For safety reasons there is a laser curtain installed in the elevator that will stop it if the light path is broken by a person or object. If this happens you may be stuck in the elevator. If for any reasons you will need to use regularly the elevator during your run please inform your SA.

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3. Troubleshooting

  1. A Troubleshooting Guide is available with instructions to solve known problems or situations that can occur at INT while observing with IDS.

  2. Several faults (and their solution) that occurred in the past are described in the Fault Database. Login as guest to search for previous fault reports. Call to the WHT OSA for advice (white phone 2559 or grey phone 452) about possible ways to solve the problem. Please use this database to log any faults you encounter. See the section Reporting/Searching faults at ING Fault Management System for more information.

  3. In case of problems that you cannot resolve easily by yourself:
    • On the first night of your run your INT SA will be available anytime by telephone. Before leaving the INT, your SA will inform you the room number from the Residencia and a mobile to contact him/her.
    • On subsequent nights, or if you cannot contact your SA, call the WHT OSA  (white phone 2559 or grey phone 452) who will try to assist you as much as possible. Note that the WHT OSA might be busy at the WHT and may not be able to visit the INT directly to solve problem or you may have to wait for a while.


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4. Areas of the Telescope

The control room is located at the top floor of the building, and has the following key areas:

  1. The Engineering Rack:
    • Manual telescope movement control
    • Remote dome movement
    • Dome sutthers operation
    • Open/close mirror cover
    • On/off dome fans

  2. The Engineering Console:
    • Dome lights
    • Emergency Stop and reset buttons
    • Computer/Engineering mode switch
    • Engineering indicator button lights
    • TV showing the dome inside
    • Speakers for dome inside sounds (check the volume).

  3. The Meteorological Data Screen

  4. The Whiteboard with important/useful information

  5. The main desk with the following computers (from left to right):
    • The slit-viewing acquisition camera computer (inttv): one screen and a keyboard
    • The TCS (Telescope Control System) and ICS (Instrument Control System) computer (lpss7): two screens and a keyboard
    • The Data Reduction PC (INTDRPC1): one screen and a keyboard

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5. Preliminaries

  1. In the control room, every day, check the Operations Logbook (usually on top of the main desk) for any restrictions that may be still in force.

  2. In the upper-left corner of the Operations Logbook, write the names of ALL observers who will be at the telescope at night. This should be repeated for every night.

  3. Turn on the dome lights (MAIN ON/OFF) from the Engineering Console and raise the control room blind.

  4. Go inside the dome and make a mindful visual inspection of the observing floor to check that the telescope is free to move e.g. no ladders or steps are close to the telescope, test instruments connected, etc.

  5. Clear any emergency overrides by pressing the RESET button next to the EMERGENCY STOP button on the Engineering Console.

  6. Turn on OIL PUMP from the Engineering Rack.

    IMPORTANT! The oil pump MUST be switched OFF at the end of the night or when the telescope will not be moved for more than an hour (e.g. if the dome had to be closed due to bad weather).

    A few seconds after the oil pump is turned off an alarm will sound. This alarm should be cleared by hitting the ACCEPT button on the Engineering Console.

  7. Before starting observations check in the INT Cass Mimic window, that you have the correct IDS configuration: central wavelength, slit width, grating camera shutter open, no ND filter, etc. Also check in the detector window, that correct detector configuration is set: binning, read out speed and window.


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6. Filling the IDS cryostat

IMPORTANT! The cryostat on IDS should be filled at least every 13 hours. During normal working week days, the ops-team working at ING will fill it at midday, so observers should fill it just before and after the observing night. During weekends and public holidays, the observer at INT is in charge of ensuring that the cryostat is filled at intervals not exceeding the 13 hour limit. If for any reason the observer at INT cannot ensure that the cryostat will be filled within 13 hours, he/she should contact the WHT Operator to coordinate the filling of the cryostat with sufficient notice. Public holidays are marked in green in ING schedule.

  • There is a sticker on each Dewar telling users to use the other Dewar if the level reaches 30%.
  • There are two Dewars and the one with more than 30% should be used.
  • Ops-team fill the dewars before the weekend, so only make a Fault Report if both dewars are below 30% on a working day which is NOT the last working day of the week.
  • Users must not completely empty a Dewar.
  • The 30% full Dewar will be used if the silicon filling tube brakes on the Dewar in use.
  • Please wait long enough before removing the silicon tube (the silicon tube should NOT be frozen when it is removed, otherwise it will break).


IMPORTANT! Wear the safety helmet (with the visor in front of your face), apron and gloves when filling the cryostat (example). BEFORE filling the cryostat you MUST mindfully read the information in the page Liquid Nitrogen Cryogenic Health and Safety.

  1. The telescope should be parked at Zenith.

  2. On the dewar top, check that the SILVER valve (gas vent) is closed. Vessels must be left pressurised.

  3. Use the indicator on top of the dewar (by pressing and holding the black rubber button) to check the dewar contains enough LN2 (>25%). If it is lower, the second dewar must be used.

  4. Check the pressure valve on the top of the dewar. The pressure should be between 0.5 and 1.5 bar. If this is not the case, use the other dewar. Please, in this case fill in a Fault Report.

  5. Slowly wheel the dewar over to the cryostat.
  6. Connect the dewar to earth; use the earthing point on the Cassegrain rotator, located above and to the left of the cryostat. 
  7. Fully insert the filler tube into the cryostat hole. Take care to hold it by the metallic tube and not the hose.
  8. On the dewar top, check that the GREEN pressure build valve is CLOSED. Then fully OPEN the BLUE decant valve. Turn the valve back by half turn from fully open, to prevent the valve freezing in this position, as it could be difficult to close it later.  
  9. Wait until liquid nitrogen is starting to leak out of the cryostat and spilling on to the floor.
  10. CLOSE the BLUE valve.
  11. Wait for the filler tube to warm up (until it is not rigid anymore) and remove it from the cryostat.
  12. Move the dewar back to the position where you found it (out of the telescope way).
  13. Write down in the Operations Logbook the time the cryostat was filled and your name.


Please, follow the safety instructions below for avoiding that anyone accidentally moves the telescope when cryostats are being filled with LN2:
  • The telescope SHOULD be in ENG MODE.

  • The telescope SHOULD be LOCKED-ON using the INT Telescope and Dome interlock Panel on the Control room.

  • Once you move the telescope ("TELESCOPIO") switch to the LOCK-ON position, gently pull the yellow handle and put a padlock in the space created for locking the switch in this position. Keep the keys of the padlock safe with you until you finish the LN2 filling and you unlock the telescope. Padlocks are in the box on top of the interlock panel.

  • The lights ("LUZ") also SHOULD be LOCKED-ON using the "INT Telescope and Dome interlock Panel". In the case of the lights it is not necessary to use the padlock.

  • Once the telescope is LOCK-ON record it in the LOG BOOK, in the same page that you fill in the information about the LN2 filling.

  • Once the LN2 filling is finished and the DEWAR is detached from the telescope and the telescope can be safely moved again UNLOCK the telescope and the lights. Leaving the padlock and keys in the place where you find them. Record in the log book that the telescope is now unlocked.



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7. Zeroset and Pointing Calibration

Note that a Zeroset ONLY should be performed if the TCS is restarted or if the telescope pointing is bad. Please call the WHT OSA before restarting the TCS or doing a Zeroset as in many cases redoing the Zeroset can be avoided.

During the first night of your run the SA will show you how to do it (in case you need to do it later during your run ONLY in the situations described above and after consulting the WHT TO).
  • Zeroset

    1. With the telescope in engineering mode, position the telescope in the zenith position.

    2. The HA and DEC dials should be correctly located, i.e. on the correct side of the labeled arrows, so that it is possible to move the telescope through the Zeroset position in the direction indicated by the arrows.

      If necessary, practice the action of moving the telescope through the Zeroset position using the HA[+]/[-] and DEC[+]/[-] (the lights above the dials will flash). Make sure you return the dials to the correct position, ready for the Zeroset, before continuing.

      Note that in HA there are two positions separated by only 13 arc minutes. Make sure to take the one closest to the indicating arrow.

    3. In the TCS User window, enter:
       USER> LOG ENC ON 10 
       USER> zeroset ha target         [or: zero ha tar]
       USER> zeroset dec target        [or: zero dec tar]
       USER> LOG ENC OFF         

    4. Using first the HA[+]/[-] button with SLOW motion selected (both QM and SM buttons will be lit up when slow motion clamps are engaged), move the telescope so that the dial pointer move through the zeroset mark in HA. After that do the same pressing the DEC[+]/[-] button, also in SLOW motion.

      NOTE: Normally, when the dials move through the zeroset positions the yellow led lights will flash and beep to acknowledge the position. Although, it might happen that the leds flash but the beep does not sound, in this case the procedure is still fine as long as the TCS acknowledges that the zeroset was completed for both HA and DEC. On the contrary, if the leds DO NOT flash, then the entire zeroset procedure must be finished first and then repeated again.

      The Zeroset needs also to be repeated if, for any reason, the TCS does not acknowledge that the zeroset was completed for both HA and DEC.

      NOTE: The DEC arrows in the engineering rack do not move correctly. Please follow the procedure described in the INT-IDS Troubleshooter (Problems zerosetting the DEC encoders section) for doing the Zeroset.

  • Pointing calibration (only after a Zeroset)

    After the Zeroset procedure described above was successfully completed, there are two possible options to indicate to the TCS which pointing calibration it should use:

    1. If the pointing before doing the Zeroset was bad, then type in the TCS User window:
       USER>  calibrate default        [or: cal def]
      This will set the default TCS pointing model. After that, a single star calibrate should be performed. If you have time and want to improve more the pointing, you can try performing a full 7-star calibrate (note that it might take ~20 min, however you can attempt it in twilight as the stars used for this test are quite bright).

    2. If the pointing was fine before the Zeroset, then type instead:
       USER>  calibrate last        [or: cal last]
      to load the TCS pointing model you were using on the previous nights.


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8. Switching the TCS between Computer and Engineering Mode

  • To set the telescope into Computer Mode, turn the COMPUTER/ENGINEERING key on the Engineering Console to the left (the COMPUTER position). The green section of the ENG/COMP push button switch should illuminate showing that Computer Mode has been selected. The system only switches to computer mode if the following three conditions are fulfilled:
    • the OIL PUMP is on
    • There are NO active emergency overrides (press the RESET button close to the ENG/COMP button)
    • HA and DEC slow motion controls (SM) are active.

    If the telescope is in Computer Mode the TCS window will say Telescope STOPPED .


  • To switch back to Engineering Mode, on the TCS type:

    USER> eng

    The ENG/COMP push button should return to yellow, showing that the TCS is in Engineering Mode. If the telescope is in Engineeringr Mode the TCS window will say Telescope ENG .


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9. Setting up the Acquisition Camera

In the orange DAS6 window on the TCS, define a 3x3 binning of the acquisition camera, which allows fast readout and display cycles. Type the command:
DAS6@miranda> bin 3 3
On the ICS mimic, check that the acquisition camera AG0 is centred on the slit. That is, in IDS mimic it should have numbers close to:

TV X: 498000
TV Y: 500000

(if these coordinates are very different please write a Fault Report and if you have problems with the acquisition inform this to the WHT TO).

Note that the TVX mechanism was disconnected and set to a fix value (498000). If you try to move this mechanism by issuing the command:

SYS> tvxy 498000 500000

you will get an error message of this type: "MECHFAIL, Mechanism fail" or "CMDTIMEOUT, Command timeout". This message must be ignored as it is a known consequence of TVX being disabled. In normal operation these mechanisms shouldn't be moved.

In ds9, you should check that the image has been inverted in the y-direction (from the top menu choose Zoom then check that the Invert Y option is checked) and that the rotation is set to '0'.

A green cross '+' for the instrument rotator centre and a red cross '+' at the slit centre should also be displayed. In case they do not appear, then from the top menu 'Region' --> 'Load Regions...', you can load the most recent region "IDS_centres_bin3" file for 3x3 binning at /home/intobs/Documents/*.reg. To load the regions you need an image being displayed. You can acquire one by pressing Field.

If the green and red crosses disappear after starting acquisition, click on ds9 top menu File, Preserve During Load, and check the box Regions.

The field of view of the Acquisition camera (AG0) covers an area of approx 75 x 70 arcsec².


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10. Loading Catalogues

Check which objects are loaded into the TCS current list of targets by typing:
      USER> out term 
If there are objects loaded which you don't need, then the command
      USER> erase 
can be used to delete all targets from the current list. Note that the catalogues will still be stored on the computer, but will no longer be loaded into the TCS.

It is possible to load your own catalogue onto the TCS with all your targets in it. They can be created with any text editor, and should be saved as {your_catalogue}.cat. The filename must not contain any upper-case letters.  Each line of the file should contain one object and its coordinates in the following format:
[object] [ra] [dec] [epoch] [!comments]
So, for an example object SN 1987A:
sn1987a 05 35 27.9 -69 16 10.00 J2000 ! comment  
The line must be delimited by spaces (not tabs!), and there should be no spaces in the object name (only underscores). They can then be loaded into the /int/cat/ directory on the ICS computer. This can be done using the scp command to copy the catalogue from your laptop to the data reduction computer (intdrpc1 or intdrpc2):
      your_laptop$ cd {directory_containing_catalogue}
      your_laptop$ scp {your_catalogue}.cat intguest@intdrpc1:/home/intguest/Desktop
and then from intdrpc1 to the telescope system:
      intguest@intdrpc1$ cd Desktop 
      intguest@intdrpc1$ scp {your_catalogue}.cat intobs@lpss7:/int/cat/
The username and password are shown on the label on the computer's monitor.
The catalogue can then be included using the command:
      USER> include {your_catalogue}   
Note: The .cat extension is not required.

It is possible to add individual objects by creating the source:
      USER> source sn1987a 05 35 27.9 -69 16 10.00 J2000 
      USER> add
the latter command is necessary to load the source into the TCS.

It is possible to remove individual objects:
      USER> remove {object_name} 
To write the contents of the current TCS catalogue to a file:
      USER> out file {your_catalogue}  
Note that to add the object you must include the epoch. No error message will be shown if you do not, but the object will not load properly.


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11. Setting up CCD and spectrograph parameters

In the ICS, check that the CCD readout speed, readout window and binning are the desired ones.

To set CCD readout speed (choices: slow or fast)

SYS> rspeed slow

To set on-chip binning:

SYS> bin x x

where the first number is the on-chip binning in the spatial direction and the second number is the on-chip binning in the dispersion direction. For example: SYS> bin 2 1 will bin x2 in the spatial direction and x1 in the dispersion direction.

To set readout window size (in pixels) from 785 to 1150 in the spatial direction, from 1 to 4200 (the whole CCD) in the dispersion direction. These values are independent of the binning set.

SYS> window 1 "[785:1150,1:4200]"

This is a default window for EEV10 CCD. For Red+2 CCD, a default window is:

SYS> window 1 "[800:1165,1:4200]"

For further information on commands regarding the CCD, refer to the UltraDAS documentation.

To set the slit width use the following command:

SYS> slitarc [x]

Where the value "[x]" is in arcsec. The slit width can take values from 0.5 to 8.5 arcsec. Example: slitarc 1, will set the slit in a width of 1 arcsec on sky. If the mechanism is send to greater values than 8.5 it can be stucked.

Different neutral density or order sorting filters can be deployed in IDS main optical path or for IDS calibration unit. For more information read the sections Neutral-density and order-sorting filters and Neutral-Density Filters for Calibrations, respectively.

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12. Neutral-density and order-sorting filters


If the target is too bright, one of the above slit neutral-density filters can be put in position, by issuing the command:

SYS> asnd 2 Moves the ND filter tray to position 2. The possibilities are 0 to 5, 5 being the strongest.
SYS> asnd 0 Takes the ND filter off.

Above Slit Neutral-Density (ASND) filters are in the A&G box.
 SYS> asnd {position} 
Where {position} is the requested filter position (0 to 5) This moves the above slit neutral density filter to the position requested.


clear

clear
2
0.4
3
0.6
4
1.1
5
2.1

Note: These ND filters are common to the science target and lamp beams, and are different from the ND filters described in the Arc/tungsten exposure subsections, which are dedicated only to the lamps.

Several order-sorting filters are also available for use (e.g. to avoid second order contamination in the red part of the spectra) in the other filter tray above the slit. The filters that are currently mounted at each tray position are:


clear

BG28

RG630
3
GG495
4
GG395
5
WG360

Below an example of the transmitted wavelength ranges, and the parts of those ranges which won't and will be contaminated by second-order light, when using the most common order-sorting filters GG395 and GG495:

Filter   Transmitted       Uncontaminated  Contaminated by
         wavelengths                       second-order
         (A)               (A)             (A)

None     3300-9500         3300-6600       6600-9500

GG395    3950-9500         3950-7900       7900-9500
 
GG495    4950-9500         4950-9500       None                 

There are more available filters that can be placed in the above slit tray, as UG1, GG385, RG695, and RG830. If you require a filter which is not currently mounted, ask your support astronomer well in advance. The wavelength dependence of transmission of these filters is given here.

The filter can be positioned by issuing the command:

SYS> ascf 3 Moves the filter tray to position 3, which has the GG495 filter (the name of the filter deployed can be read in the INT Cass Mimic). The possibilities are 0 to 5.
SYS> ascf 0 Takes the filter off.


Note that the use of filters above the slit introduces an offset to the telescope focus.
If you are going to observe with and without filter (or with different filters) in the same night, the best would be to find the best telescope focus with/without filter (or with each filter) and change the telescope focus to the correct value every time you change the filter configuration (it can be good to make a script for doing this).


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13. Preparing the Autoguider

Suitable guide stars can be found using a graphical user interface to the Guide Star Catalog. If the GSS2 interface is not already visible, open a terminal on the display machine inticsdisplay (click on the terminal icon on the desktop) and type:

intobs@inticsdisplay> ssh -Y gss@intgss

Login as gss (the password should be written on the whiteboard. If not, ask your support astronomer or the WHT telescope operator).

[gss@intgss ~]$ gss2

A new window with the graphic user interface for Guide Star Search will be displayed. This will be used later for selecting appropriate guide stars.

NOTE: Do not forget to set the gss2 configuration to INTCass.

The Autoguider field of view is about 80 x 60 arcsec².

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14. Sky Orientation in the acquisition camera

This is the orientation WITHOUT any image rotation. Note that if you followed the instructions in Setting Up the Acquisition Camera and invert Y you will see East UP and North right in the TV slit-viewing camera.

sky PA = 0 sky PA=90 sky PA=180 sky PA=270 ------> N E <------ E N | | ^ ^ | | | | | | | | V V | | E N N <------ ------> E
At the INT control room there is a hand made "graduated circle" that can be used to determine the orientation at other sky PAs. This circle gives the sky orientation in the acquisition camera when the Y-axis is inverted in DS9.

When a certain sky position angle is not required (for example for a single point source), it is recommended that the sky PA matches that of the parallactic angle of the target. Mounting a PA of this value puts the slit along the longest axis of the star, elongated by atmospheric refraction. As such, this becomes even more important towards low elevation.

The parallactic angle of the object can be seen on the TCS info display underneath the information of the current mount PA. The value is constantly changing with time, and a PA should be chosen so that it roughly matches the parallactic angle of the target in the middle of the exposure.

The parallactic angle of multiple targets can be calculated in advance using the STARALT tool. Note that the parallactic angle option should be chosen instead of moon distance.

Because the Cassegrain rotator is slow, overheads can be reduced by calculating the required PA before each new target, and sending the command to change the sky angle (see "rotate sky" in Target Acquisition) immediately after issuing the "gocat ..." command.


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15. Calibration frames

Test exposure: glance

SYS> glance {exp_time} Takes a {exp_time} seconds exposure which is saved as s1.fit. New glances will overwrite previous ones. Useful to check exposure times.

Biases

Check that the dome lights and internal IDS lights (in the A&G) are OFF.

SYS> bias Takes a bias exposure.
SYS> multbias {n} Takes n bias exposures.

Arcs

SYS> compmirror in Places the comparison mirror in the beam.
SYS> complamps {lamp} Turns on the required lamp. Options for lamp are: CuAr, CuNe and CuAr+CuNe. Note that it is case sensitive.
Example: SYS> complamps CuAr+CuNe
SYS> arc {exp_time} Takes an arc image of 'exp_time' seconds.
SYS> multarc {n} {exp_time} Takes 'n' arc images of 'exp_time' seconds.
SYS> complamps off Turns off lamps.
SYS> compmirror out Removes comparison mirror from beam.

The script runarc performs all the steps to take an IDS arc (compmirror in, complamps cune+cuar, takes arc, complamps off, compmirror out). This is particularly useful to take a single arc frame during the night before/after observing the science target. Note that the guiding does not get lost when taking an arc so it is possible to do the acquisition, take an arc afterwards and then proceed with the science observation.

To run the scrip:

SYS> cd Changes to the home directory.
SYS> runarc {exp_time} Does all the steps to take an arc of 'exp_time' seconds and turns off the lights and removes comparison mirror when finished.


Internal W-lamp flats

SYS> compmirror in Places the comparison mirror in the beam.
SYS> complamps W Turns on Tungsten (white) lamp. Note that it is case sensitive.
SYS> flat {exp_time} Takes a 'exp_time' seconds flat with the tungsten light.
SYS> multflat {n} {exp_time} Takes a 'n' flat frames of 'exp_time' seconds flat with the tungsten light.
SYS> complamps off Turns off lamps.
SYS> compmirror out Removes comparison mirror from beam.

If the counts are too high for exposure times of less than 1 sec (this may occur when using low resolution gratings in red central wavelengths), then you might need to use the neutral-density filters dedicated to the lamps (0 to 7, where 0 is no filter and 7 is the strongest).

SYS> compfilta 1 Moves the comparison filter wheel A to position 1.
SYS> compfilta 0 Takes off the comparison filter.

At the end of this manual you will find a list with the positions of the neutral-density filters available for the calibrations.

The script runmultflat performs all the steps to take a series of IDS lamp flats (compmirror in, lamps W on, takes multflat, lamps off, mirror out). To run the scrip:

SYS> cd Changes to the home directory.
SYS> runmultflat {n} {exp_time} Does all the steps to take 'n' flat frames of 'exp_time' seconds each one and turns off the W-light and removes comparison mirror when finished.

Spectroscopic sky flats

We recommend to take twilight sky flats.

Although the sky flats present many absorption lines, the sky illumination is more homogeneous ('flatter') than the W-lamp. Thus, twilight sky flats are usually used to determine the slit illumination function (in the spatial direction). Knowledge of this is crucial when observing extended targets or two (or more) targets simultaneously in the slit, and is useful for accurate sky subtraction.

Note that the sky-flats DO NOT replace the W-flats. The W-flats, being free of lines, are necessary for determining the CCD's pixel-to-pixel response.

To take twilight sky flats, telescope should look at the sky light. Leave the telescope at Zenith position in engineering mode (i.e. no tracking). No offsets between individual flats are needed. The dome and mirror petals should be opened and the comparison mirror should be out of the light path.
Aim for approximately 30,000 - 35,000 counts in a single exposure.
For a higher resolution gratings (R1200U, R1200B, R1200Y, H1800V, H2400B), you should start 10-15 minutes before sunset. For lower resolution gratings it is enough to start around sunset.

SYS> compmirror out
SYS> sky {exp_time} Takes a 'exp_time' seconds sky flat.
SYS> multsky {n} {exp_time} Takes 'n' exposures of 'exp_time' seconds each.


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16. Opening Up

  1. Check that the weather conditions allow for opening the dome:

    • Weather should be stable (for about the last 20 minutes before opening) with humidity lower than 90%
    • Wind below 80km/h
    • Local Mast sensor should be "DRY" (NO rain or wet)
    • .
    In case of doubt call WHT OSA for advice.
  2. Set the humidity alarm to 75%. If the humidity is higher than 75% then set the alarm to 90% and immediately close the dome if humidity rises higher than 90%.

  3. Walk at least one floor down, call the lift and turn the lights off.

  4. Open the south doors, latching them safely to the walls. South doors can be opened only if:
    • The humidity is below 75%
    • The wind speed is below 40km/h
    • The wind gusts are below 48km/h
    In case of doubt call WHT OSA for advice

  5. Switch all dome lights off, as well as the lights in the far end of the control room.

  6. Rotate the dome towards the East (in the direction of the doors to the lift) using the DOME ROTATION CW (clockwise) and CCW (counter clockwise) buttons found just right of the UPPER SHUTTER panel.

  7. On the UPPER SHUTTER panel (located on lower engineering rack), use RAISE MICRO until the MAIN OVERTRAVEL light underneath turns off and you hear a 'clunk'. Then push RAISE MAIN until the shutter stops moving. To fully open the upper shutter push RAISE MICRO until the shutter stops moving again.

  8. Push and hold the MIRROR COVER OPEN button. The light below the MIRROR COVER buttons will change from green (closed) to red (open) when finished.

  9. Push the DOME VENT FAN ON button to enable dome ventilation. The red light will go OFF when the ventilator is on. If the humidity rises above 75%, the dome fans must be turned off.

  10. Close the control room blind.

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17. Procedure for a 7-star and single star calibrate of telescope pointing

Using a single star calibration will improve the pointing model, and should be sufficient to use for the rest of your observing run, unless the TCS has to be restarted.
If you find poor pointing on subsequent nights, it could be because the TCS has been restarted during maintenance checks. If this is the case, simply repeat the single star calibrate procedure.

Begin taking image frames with the TV acquisition camera by clicking the TV button. Adjust the exposure times if necessary using the top box, and pressing RETURN.

USER> enter aperture 0 0 0 This centres the aperture on the rotator +32 33 03.8153 centre.
USER> cal faint This sends the telescope to a suitable faint calibration star and begins the 7-star calibration procedure.
HANDSET> Press INSERT key This is to exit the HANDSET menu immediately after it appears in the TCS window

Failing to break out of the HANDSET menu at this point will continue with the procedure of the 7-star calibrate, which is similar to the single star calibrate but using 7 stars, correcting more parameters in the pointing model. Doing the 7-star calibrate takes longer time and it is not needed as it was done and saved already in the previous D-night by an INT SA.

If the star appears directly on the green cross + (which marks the rotator centre), the pointing is fine and you can skip the rest of this section. Otherwise, you need to use the 'HANDSET'  button again to centre the star on the green cross +.


      USE OF THE HANDSET

  • Press the 'HANDSET' button  (INSERT) on the TCS keyboard to enter HANDSET mode.

    If INSERT is not working, type USER> HANDSET to enter HANDSET mode. The key F6 also enters the HANDSET mode, provided the keyboard mapping for the TCS is working fine.

  • Press "F10" to select X_Y offset for Single Star Calibrate.
    The Single Star Calibrate MUST be done offsetting the telescope in X_Y, otherwise the correction may not be applied.

    Note that even when the TCS key mapping is lost, it will be still possible to select any of the ALT_AZ, RA_Dev and X_Y modes.

  • When using the AUTOGUIDER the offset mode needs to be selected with "a" to select appoff (aperture offset) which allows the autoguider to allow handset movements.

  • The '<' and '>' keys will set the offset step in arcseconds, from 0.3 to 100.

  • Pressing the arrow keys will move the telescope in the direction indicated. Wait for the acquisition TV to catch up with each movement before moving again.

  • Pressing the key  INSERT again will exit the HANDSET mode. Alternatively, pressing <ctrl-z> also breaks out the HANDSET menu.

Once the star is well centred on the green cross, exit the HANDSET (by pressing INSERT button) and type:

USER> point calibrate (point calib)

USER> cal anal zero

Typically the rms of the solution will be around 0.01, as only one star was used. Unless the rms of the solution is very high (>0.05), type "Y" to accept. Otherwise type "N" and repeat the procedure.


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18. Focusing the telescope


Below are described the two possible procedures to determine the best telescope focus: i) Focus run using the script and ii) Manual focus run. In both cases it is necessary to point the telescope to a suitable star (V~9-11) at low airmass. You can select a target from the ING Spectrophotometric catalog.

Set the filter configuration to be used for the science exposures (the best telescope focus may change significantly for different filters).

Point the telescope to the selected star:

USER> gocat {SPXXXXXXXX}

Use the HANDSET to centre the star on the centre of the slit (red cross).

Keep the same slit width as you will use for your science observations. If the slit is too narrow (< 1 arcsec) or if the seeing is bad, it might help to open the slit so that we get enough light from the star to focus.

Always set the guiding for focusing, to avoid the star to drift from the slit during the focus run sequence.

Check the exposure time you need to integrate so that you get good signal in the continuum of the star to fit it with a gaussian profile. The exposure time, on the other hand, should be long enough to avoid sampling the seeing variations (longer than ∼ 5 s).

Use fast readout speed:

SYS> rspeed fast

i) Focus run using the script

  1. Call the script that takes the images for the focus run:

    SYS> focusrun.py

    Four questions will be prompted in the screen to set the parameters for the script:

    • Question: what starting value would you like for the focus?
      Example of answer: 15.8
      It is good to set this value ~0.2 mm below the last known focus (see white board). As IDS nominal focus is ~16.0 mm (with no filters), starting with 15.8 mm is usually good choice.

    • Question: what step size would you like for the focus?
      Example of answer: 0.05

    • How many steps do you need?
      Example of answer: 9
      (Note that this is actually the number of images that will be taken)

    • what exposure time (in s)
      Example of answer: 10

    After setting these parameters all the focus run images will be acquired.

  2. In an IRAF terminal run the ids_starfocus script as follows:

    ecl> !ids_starfocus

    (note the use of the exclamation mark '!' at the beginning of this command)

    This script will prompt a short series of simple instructions in the screen to guide you to obtain the best telescope focus. Basically, the script will ask the first image run number (e.g. r1059172) and the number of images taken in the focus sequence. The first image will be displayed in ds9, then you should point the cursor in the continuum of the star, around the center of the image in the dispersion direction (y~2100 pix) and press 'g' to measure the spatial profile at that position. All images in the focusrun sequence will be displayed in turn and for each one a Gaussian fit will be performed and displayed. Once the images are measured, a window will open showing a plot of the measured values of FWHM versus the telescope focus and a parabolic fit. The best empirical and fitted telescope focus values will be printed in the IRAF terminal as well. Check these results, choose the appropriate focus value and close the plot window (you can save the plot if you want, the script will ask).

  3. Once you have chosen the telescope focus set its value by typing

    SYS> focus {xx.xx}

    and set slow readout speed:

    SYS> rspeed slow

ii) Manual focus run

  1. Set the focus to a value 0.2 mm below the nominal focus value:

    SYS> focus {xx.xx}

  2. Take a 10 second exposure labeled with the current focus position. Do not take exposures shorter than 8 seconds to avoid sampling the seeing variations:

    SYS> run 10 "focus {xx.xx}"

  3. Display each image in IRAF:

    ecl> display r{run number}[1] 1; imexam

    Along the dispersion direction, choose a region around the middle of the detector and measure the FWHM of the spatial profile of the spectrum by placing the cursor over spectrum and pressing the 'j' key. Make sure to measure the FWHM of the same point in the spectrum by creating a region in the ds9 - this can be done by a simple left-click.

  4. Keep incrementing the focus value and taking exposures incrementing the focus value by 0.1 mm (or 0.05mm if the seeing is good) and measuring the FWHM until you notice that the FWHM is clearly getting worse.

  5. Once you have found the minimum FWHM, set the telescope focus to the value that gave the smallest FWHM.

    SYS> focus {xx.xx}

    and set slow readout speed:

    SYS> rspeed slow


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19. Target Acquisition


Ensure your target is included in the catalogue loaded in to the TCS (see Loading Catalogues section). To slew to your target type:

SYS> gocat {catalog_target_name}

The telescope will point to that target in your catalogue. Note that spectrophotometric standards and other lists of bright stars are included by default  in the system catalogue

SYS> rotate sky {xxx}

This moves CASS rotator mount to xx degrees, which corresponds to the position angle (PA) of the slit in the sky.

DO NOT try to move to a position angle between 138 and 142 degrees, as it will push the rotator out of its limits. Instead use angles from 318 to 322 degrees.


Press TV in the "SDSU Autoguider on AG0" grey window to start the continuous readout mode of the slit-viewing camera. You can adjust the exposure time for each frame in the top box - press RETURN to initiate the new exposure time.

Use the HANDSET mode (F6) to move the target on to the slit centre (red cross '+').

The field of view of the acquisition camera (AG0) covers an area of approx 75 x 70 arcsec².

TV camera filters (acquisition camera):

There is a set of filters dedicated to the acquisition TV camera. They are particularly useful for bright objects, for a more accurate acquisition.

To use the filters type:

SYS>tvfilt x

where 'x' is the filter position.

The numbers associated to each TV filter are listed in the following table:


Clear

Green (BG38)
2
Blue (BG28)
3
Red (RG630)

Hence,

SYS>tvfilt 2

will deploy the blue (BG28) filter (which is in position 2).

Autoguider camera filters:

There is a set of filters dedicated to the autoguider camera which can be used in a similar way as the acquisition TV camera filters.

To use the filters type:

SYS>autofilt x

where 'x' is the filter position.

The numbers associated to each autoguider filter are listed in the following table:


Clear

Green (BG38)
2
Blue (BG28)
3
Red (RG630)

Hence,

SYS>autofilt 2

will deploy the blue (BG28) filter (which is in position 2).

To save acquisition camera images

Images of the acquisition camera, AG0, can be saved and stored in the same directory that the science images. Note that AG0 and IDS detectors (Red+2 or EEV10) are independent detectors so AG0 images can be taken simultaneously with science images, hence this procedure does not add overheads to observations.

To save AG0 images proceed as follows:

  • After finishing the acquisition and starting to take science images stop the TV mode in the acquisition camera

  • In the orange DAS6 window on the TCS, type the command:
    DAS6@miranda> run [x]
    where "[x]" is the exposure time in seconds. Example: run 30 will take an image of 30 seconds exposure time.

  • Note that the images of the AG0 are not science grade images but they are useful as a reference when doing the data reduction (and they do not take extra time). These images will not have a complete header as the IDS images. These images will be listed in the night log and stored in the directory of the night together with the science IDS images.

  • After finishing the AG0 exposure do not forget to turn ON the TV mode in the acquisition camera.

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20. Guiding


It is strongly recommended that you use guiding if the time on the target is longer than two minutes.

  1. While the telescope is slewing to your science target (including the correct SkyPA), in the Guide Star Search Interface window (GSS2) enter the coordinates of the target.

  2. Select INTCass from the Configuration menu.

  3. Fill in the Rotator SkyPA box with the Mount PA shown on the TCS DISPLAY screen (not the parallactic angle).

  4. Set the aperture offset values to the X/Y HANDSET offsets applied to acquire the target. If no HANDSET offsets were applied then set the aperture to 0.

  5. Click SEARCH.

  6. The GSS2 Interface will now display a list of potential guide stars. Select a guide star ideally between 11-13th mag and highlight the X/Y position which automatically copies text and execute the following commands:

    SYS> autoxy xxxxxxx yyyyyyy

    This centres the autoguiding probe at the X/Y position xxxxxxx yyyyyyy. This is the position copied from the GSS2 in the previous step (to paste it just press mouse middle button).

    SYS> field

    This takes an image in the autoguider and searches for potential guide stars at this position (be aware that some detections can be hot pixels and not real stars!). Sometimes it might be necessary to change the exposure time in the autoguider to obtain a good signal for the autoguider to work properly.

    SYS> guide on star xx

    This will guide on the star marked as star xx, where xx is the number that appears in the Autoguider image after the field has been taken.

    There are also some Action keys: PAGE UP and PAGE DOWN, to invoke AUTO ON and AUTO OFF, respectively.

Note: If small corrections of the telescope position are needed while guiding, use the HANDSET (INSERT on the TCS keyboard) in APOFF offset mode ("a" on the TCS keyboard).

Failing to find guide stars

No suitable guide stars in GSS2 at certain SkyPA

Sometimes it's not possible to find suitable guide stars for the required Sky Position Angle (PA). When this happens, the first step one should take is to search with the opposite slit PA (PA - 180). If this does not resolve the problem and in the case of long exposures where an average PA (e.g. average parallactic angle) is usually chosen, small PA changes can be tried (5-10 degrees). If this also fails, the alternative is to guide manually by opening the HANDSET tool (F6 on the TCS keyboard) and applying the necessary corrections to maintain the target over the red crosshair inside the slit. If the target is not visible and there are other stars in the FOV, then one of them can be used for manual guiding by creating a region around it and keeping it inside that region during the exposure.

Predicted star by GSS2 does not appear in the Autoguider field

The Autoguider field of view is about 80 x 60 arcsec².

Sometimes, it can happen that the predictions of the GSS2 are not accurate (particularly when the x,y offsets are large) and no guide star is seen in the Autoguider field after the probe was moved to the predicted position.

If you followed the standard procedure for guiding and you do not find a guide star in the Autoguider field, try the following workaround:

  • GOCAT to the science target and acquire it into the slit applying X/Y HANDSET offsets.

  • Search in the GSS2 a guide star there, set the aperture offset values to the X/Y HANDSET offsets applied.

  • Move the guide probe to the position provided by the GSS2 and set the Autoguider in the "TV mode" (so it keeps on taking images continuously). Leave the Autoguider in the "TV mode" during the whole procedure until you are ready to start guiding. This is convenient for two reasons:
    • If you need to move the probe to keep the guide star centred you need to see which way it is moving and how far it moves as you move the probe.
    • In case you are doing a blind-offset you will see immediately if the guide star appears or not if the TV mode is already running and you don't have to waste time doing a "Field".

  • If the predicted guide star does not appear on the autoguider window, try making changes to the autoguider probe positions using the command "autoxy {xxxxxx} {yyyyyyy}" and changing the {xxxxxx} and {yyyyyyy} value, until you see the star on the window.

  • As a reference, the Autoguider field of view in Autoguider units is 15000 x 10000.
    An increase of 7500 units in the value {xxxxxx} will move the guide star half of the Autoguider screen to the left. An increase of 5000 units in the value {yyyyyy} will move the guide star half of the Autoguider screen down.

  • Start guiding as soon as possible.


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21. Faint target acquisition

If the science target is too faint to be acquired directly into the slit, then a blind offset should be used.

The limiting magnitude for an effective acquisition is around V = 17 mag, for dark/grey sky brightness and bad seeing conditions (~ 2 arcsecs). If the seeing is good, it can be possible to go a little bit fainter.
Note that the acquisition of fainter targets is possible, but the longer exposure times (>60 secs) on the acquisition TV may not be efficient.

To acquire with a blind offset it is necessary to select a bright target as close as possible from the faint target and include it in the catalogue. To avoid loosing night time, it is highly recommended to have previously prepared the bright targets for blind-offset and have included them already in the catalogue. Nevertheless, if necessary, it can also be done on the fly using source and add commands.

For the blind-offset to work properly it is necessary that the coordinates of the science target and the bright target used for the blind-offset are from the same astrometric catalogue and that the proper motions of both targets are taken into account.

Note:

  • Up to 8 arcminutes, the blind offset has proven to be extremely accurate.
  • Further more, untill 15 arcminutes it still works well (within 0.5" shift).
  • For more than 20 arcminutes, the difference becomes noticeable (the shift can be ~ 1-1.5") and is not recommended unless you will use a wide slit.

Most probably, if you require to use a blind-offset for acquisition, then you will guide during the exposure. Therefore, the procedure to acquire a target and start guiding using a blind offset is as follows:

To be able to start the Autoguider immediately after the blind offset, first you need to find a suitable guide star at the position of the faint target. To do so, proceed as follows:

  • Point the telescope to the bright blind-offset target and set the PA of the science target:

  • SYS> gocat {catalog_blind-offset_target_name}
    SYS> rotate sky {xxx}

  • Acquire the blind-offset target as good as possible. That is, enter the HANDSET mode and centre the blind-offset target in the slit position you would like the science target to be.

  • Search for a suitable guide star in the GSS2 interface, entering there the science target coordinates, the corresponding SkyPA and in the Aperture Offset for X and Y you should write the offsets made with the HANDSET to position the blind-offset target well in the slit and press SEARCH.

  • Choose from the displayed list a suitable guide star and centre the autoguiding probe at its X/Y position:

    SYS> autoxy {xxxxxx} {yyyyyyy}

  • Check now that the blind-offset target is still in the good position in the slit (otherwise fine-tune the position if necessary) and bring the faint science object into the slit with the command:

    USER> blind {catalog_science_target_name}

  • Note that you won't see the faint science object in the acquisition camera.

  • Take an image of the field in the Autoguider and start guiding:

    SYS> field

    SYS> guide on star {xx}

    This will guide on the star marked as star {xx}, where xx is the number that appears in the Autoguider image after the field has been taken.

  • Once the guiding is stable (e.i. the x/y errors do not get lower anymore) proceed to take your science images. Usual guide x/y errors displayed in the TCSinfo are about ±0.1/±0.2 arcsec. Note that these numbers depend on the current conditions (e.i. the guide star, sky transparency, exposure time for the guiding, etc.) and are quote here only as a reference.

Note: Coordinates of both the bright blind-offset object and the faint science object must be in the same astrometric system and both with precision of at least 0.01 seconds in RA and 0.1 arcsec in dec. It is Also important that the coordinates of the blind-offset targets include the proper motions up to the observing date.

Caution: A blind offset should not be executed if the guiding loop has been closed on the reference object. For example, if a bright target in a galaxy or cluster is observed closed-loop, followed immediately by a blind offset to a faint target in the same galaxy or cluster, the acquisition of the faint target will be compromised. Therefore, a correct procedure in this case would be to acquire a reference object again, prepare a guiding star, and without closing a guiding loop apply a blind offset, and start guiding quickly.


If you have problems to find a guide star follow the recommendations at Failing to find guide stars.

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22. Observing at low elevation (Altitude<33°)


If you want to observe at elevations below 33 degrees (zenith distance (ZD) between 57 and 70 degrees) then you need to raise the lower shutter. There will not be any warnings given from the telescope control, so you will have to check the ZD from time to time. With the lower shutter raised it is possible to observe targets with elevation between 20-34 degrees.

  1. Close the mirror petals (if they were opened) to protect the telescope mirror.
  2. Push the yellow button under SELECT MANUAL CONTROL, labelled DOME SHUTRS to get the control of the shutters.
  3. On the engineering rack, under LOWER SHUTTER, push the RAISE MICRO button until the MAIN OVER TRAVEL light underneath goes off.
  4. Follow by pushing the RAISE MAIN button; while raising, you will hear bangs caused by the segments of the shutter catching the next one. Keep the button pressed until you hear the motor stops. This takes approximately 30 seconds.
  5. Then press RAISE MICRO button again for a few seconds until the lower shutter completely fits with the upper shutter.
  6. Release the DOME SHUTRS button, otherwise the dome will no longer track the object.
  7. Go to the dome with a torch and check that the shutters are properly opened, so that there is no gap between the upper and lower shutters.
  8. Open the mirror petals.

You can now observe below 33 degrees elevation.

Remember to bring the lower shutter down again when you go to a new source above 40 degrees elevation. To do this:

  1. Close the mirror petals to protect the telescope mirror.
  2. Select manual control as before with the DOME SHUTRS button.
  3. Push the LOWER MICRO button to start lowering the lower shutter. Keep the button pressed for approximately 10 seconds.
  4. Push the LOWER MAIN button to bring the shutter down as far as it goes.
  5. Push the LOWER MICRO button to fully lower the shutter. Keep the button pressed for approximately 10 seconds to be sure.
  6. Release the DOME SHUTRS button, otherwise the dome will no longer track the object.
  7. Open the mirror petals.

Note: If the bottom shutter is not fully lowered, then the upper shutter will not completely seal the dome at the top and rain/wind will penetrate into the dome.

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23. Observing targets moving at non-sidereal rates


If you want to observe a target that moves at a non-sidereal rate (e.g. a solar system object such as a comet or an asteroid) the TCS needs to be told to track at a different rate from sidereal.

The differential rates in RA, dRA (in seconds/second) and Dec, dDec (in arcseconds/second) in the Equatorial Coordinate System, should have been previously calculated for all times during the night when observations might be wanted, as well as the RA and Dec at these times.

The differential tracking rates are then input to the TCS using the following sequence of commands:

 USER> gocat {object_name}
 USER> diff_rates dRA dDec
 USER> next

Check that the TCS shows that a differential tracking rate has been applied: a line near the top of the TCS Display should say "Differential Rate dRA dDec".

There is no autoguiding mode available for IDS using differential rates. Corrections need to be applied manually to keep the object within the slit (every 2-3 minutes), using the HANDSET.

To return to sidereal tracking (e.g. for standards) issue the TCS command:

 USER> diff_rates 0 0


NOTE: The TCS requires the differential tracking rates to be expressed as:

    dRA = d(RA)/dt         [in SECONDS/sec]
    dDec = d(Dec)/dt      [in ARCSECONDS/sec]

Sometimes, ephemerides are given as:

    dRA = d(RA)/dt x cos(Dec)       [in ARCSECONDS/hour]     (1)
    dDec = d(Dec)/dt                        [in ARCSECONDS/hour]     (2)

Thus, to transform these for TCS input, compute:

    dRA = (1) / (3600 x 15 x cos(Dec))         [in SECONDS/sec]
    dDec = (2) / 3600                                      [in ARCSECONDS/sec]

In case the ephemeris server gives you two options, chose "coordinate motions" instead of "sky motions", so you don't have to divide dRA by cos(Dec) anymore.


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24. Observing Commands


Here follows a list of the most commonly used commands throughout the night. See also the ULTRADAS Dictionary for commands related to exposure definition and CCD parameters settings.

Remember that the lower shutter starts vignetting at ZENITH DISTANCE >57 degrees (ELEVATION <33 degrees) - the system does not warn you! If you need to observe at ZENITH DISTANCE > 57 degrees, please follow the instructions described in Section 22.

talkerBellINT command

The talkerBellINT command produces a beep from the INTICS computer. It is useful to use when you want to be warned that a previous command was finished, for example:

SYS> run 1800 ; talkerBellINT

will produce a beep after the exposure of 1800 sec has finished the readout.

It is case sensitive so it should be written with the capitals (as shown in the example above). Just in case, check it before using it to adjust the volume on the speakers to hear it properly. To check it just type:

SYS> talkerBellINT

Science exposures

SYS> run 1200 "XXXXX" Exposes for 1200 seconds and name the image XXXXX. Note that if you don't specify a comment, the observing log automatically sets as a comment, the target name written in your catalogue.
SYS> multrun 3 120 "XXXXX" ; talkerBellINT Takes 3 consecutive exposures of 120 seconds each. The talkerBellINT will beep after the sequence is finished. See talkerBellINT command section above.

At the end of the exposure, if you want to move to another target:

SYS> guide off Stops guiding.
SYS> guide on Recovers the guiding in the same guide star if telescope is not moved.

If you won't be using the acquisition camera for a while, press Stop in the "SDSU Autoguider on AG0" to stop readout of acquisition camera.

Interrupting exposures

There are three commands that affect observations which are already running. To get the prompt back while an observation is running, press <Ctrl>-z (in the ICS window) and then type one of the following commands:

  • The command abort terminates an observation started by run and similar commands. The observation is not saved to disk. If the run was part of a multiple-exposure sequence (started by multrun etc.), abort terminates the current run and all subsequent runs of the sequence.

    SYS> abort


  • The command finish terminates an observation started by run and similar commands. The observation is saved to disk as if the full integration time had expired. If the run was part of a multiple-exposure sequence (started by multrun etc.), finish only alters the current run. Other runs in the sequence carry on.

    SYS> finish


  • The command newtime alters the demanded exposure-time of the observation currently in progress. If the new demanded time is less than the time already exposed, then the exposure ends immediately as if the command was finish.

    SYS> newtime {new-exposure-time}


If you were running a script that will execute more ICS commands than taking exposures (e.g. turning on calibration lamps, setting the calibration mirror, etc) you have to terminate the script. To finish the script you can try:

SYS> <Ctrl>-c

If this does not work then you can do:

SYS> <Ctrl>-z

Then check the suspended jobs by:

SYS> jobs

and kill your script via:

SYS> kill %n

where n is the job number (not the PID!).

Sometimes just kill %n is not enough. In this case you should use kill -9 %n.


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25. Observing scripts

The observers could use their own observing scripts to observe a given sequence, given an object (ex. obj1) was previously defined in the catalog, using standard observing commands.

First, from your laptop you have to FTP your script (example johnscript) to the INT system:
      sftp intobs@intdrpc1
Second, you have to change directory to:
      sftp> cd /home/intobs
Third, you have to put your script there:
      sftp> put johnscript
Fourth, change its permission for execution there:
      sftp> chmod 555 johnscript
Finally, from the INT ICS terminal in the same /home/intobs/ directory, you can run the script by simply entering its name at the prompt, namely:
      SYS> johnscript
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26. Examining Data

Note: If you plan to reduce your data on the INTDRPC1 remember that you must not operate on the images stored in the /obsdata directory (in particular, NEVER move or delete the image files).  You can create a directory in the /scratch folder (e.g. /scratch/inta/20111005) or in the /reduction/local folder on INTDRPC1, and copy the images there to proceed with your own data processing. This should not be a substitute for backing up your data as these files are periodically wiped clean.

Data format

In IDS data from Red+2 and EEV10 detectors the y-direction (detectors columns) corresponds with the dispersion direction while the x-direction (detector rows) with the spatial direction.

In Red+2, the wavelength range in the images goes from blue to red. Lower y-pixel positions correspond to lower (bluer) wavelengths and higher y-pixel positions correspond to higher (redder) wavelengths. For the EEV10 this is inverted, hence lower y-pixel positions correspond to higher (redder) wavelengths and higher y-pixel positions correspond to lower (bluer) wavelengths.

The spatial x-direction remains the same in both detectors.

IDS images are MEF files. The full image header and the spectrum are on the extention [1].

Images from AG0 acquisition camera, are not science grade images and they will not have a complete header as the IDS images. These images will be listed in the night log and stored in the directory of the night together with the science IDS (Red+2 and EEV10) images.


Manual image check with IRAF

First, close any active IRAF sessions on the INTDRPC1 computer. Then issue the command iraf in a terminal window. This will open an xgterm window, a ds9 window and execute IRAF automatically.

The IRAF interface on the Data Reduction System (INTDRPC1) is used to examine the data. From the IRAF prompt, make sure you are in the correct directory (today's directory can be found at the bottom of the udas_camera_mimic display on the ICS) or change to it by:

ecl> cd /obsdata/inta/yyyymmdd

where yyyymmdd is today date in the format year-month-day.

Use the following IRAF command to display the image:

ecl> display r242645[1] 1 ; imexam

It loads the 2D spectrum of image number r242645 in the ds9 window. Note that for Red+2 detector images, the spectral dispersion goes from blue (lower y-pixel positions) to red (higher y-pixel positions). For EEV10 detector images, spectral dispersion goes on the opposite way, from red (lower y-pixel positions) to blue (higher y-pixel positions). The imexamine IRAF command allows for quick examination of the data.

Useful imexamine key commands are listed below. The letter has to be typed:

- 'j' for Gaussian fit along a line (spatial direction)
- 'k' for Gaussian fit along a column (dispersion direction)
- 'v' for vector cut; click start and end
- 'c' for column cut
- 'l' for line
- 'e' for elliptical plot
- 's' for surface plot
- 'm' to obtain pixel statistics on section around cursor
- 'r' for radial profile
- 'q' to quit imexam

For a complete imexamine help:

ecl> help imexam

Checking the data quality

Before observations, specially at the beginning of each run, it is important that observers make a quality check of their data:

  1. Take an arc with a slit width narrow enough (1 - 1.5 arcsec), display the image in IRAF, and check the FWHM of several single arc lines with imexamine and 'k' letter typed over each arc line. Check the final FWHM and compare it with the expected FWHM for the slit projected to 2 pixels at detector in IDS Gratings tables (7th column). The final FWHM differs slightly for each detector, and also for each grating due to the grating magnification. For example for Red+2 detector, R150V grating and 1.03 arcsec slit width, FWHM should be around 2 pixels for each arc line. You should find the same FWHM, 2 pixels, for Red+2 detector and H1800V grating, but with 1.4 arcsec slit width. Make sure that your measurements meet expectations. An example of the good and bad spectrograph focus with a slit width of 1.5 arcsec, grating R400V and EEV10 CCD can be seen on this picture.

  2. On a point source exposure (for example of a standard star or a star used for focusing the telescope, after the telescope focus is set to the best value), check also the spatial profile of your spectrum. Display the image in IRAF, and with imexamine use 'j' letter typed over the spectrum. Measure the spatial profile close to the center of the CCD, that is around pixel y=2100, to avoid regions close to CCD edges where the optical quality is worse. Check that the final profile is Gaussian (no double peaks or asymmetries present), and also that the FWHM of spatial profile agrees roughly with the seeing on site. In general the seeing at INT is worse than the seeing at WHT DIMM, which is measured at different site, with a different technique and close to Zenith. The seeing is typically around 0.5 arcsec higher at INT than at WHT DIMM. The spatial scale on IDS with Red+2 detector is 0.44 arcsec/pixel, and with EEV10 detector 0.40 arcsec/pixel.

  3. If you find that FWHM of arc lines is much larger than expected, or your spatial profile is not Gaussian, it is likely that the spectrograph set-up has to be corrected. Ask your support astronomer for help.

Quick-look spectrum extraction

Note: To use the ids_ql task first copy the required data to a scratch area, e.g. /scratch/inta/"directory".

You can run the IDS quick-look script at IRAF as follows

ecl> ing

ecl> ids

ecl> ids_ql rxxxxxxx zzz

where the image name is given without the '.fit' extension and zzz is the approximate x position of the spectrum on the CCD (not dependent on binning). The script carries out an optimal extraction (takes ~ 1 sec) and displays the spectrum in the iraf graphics window using splot, so all the usual keystrokes are available. No wavelength calibration is provided.

Note that the Signal-to-Noise you calculate for your spectrum might be under-predicted with respect to the estimation from the Exposure Time Calculator. It might needs some update including new throughput test results. Last throughput test was performed in 2011 when commissioning the Red+2 detector. It has been a longer time since last throughput tests was carried out for EEV10. The reflectivity of the optical surfaces might have been degraded over the years. The reflectivity degradation might affect in a different way at different wavelength ranges and resolutions (gratings).


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27. Closing down at the end of night

  1. Check that the acquisition camera AG0 and the autoguider are not reading out (press Stop in both windows).

  2. Push the DOME VENT FAN STOP button to turn off dome ventilation. The red light will go on when ventilator is stopped.

  3. Push and hold the MIRROR COVER CLOSE button. Check the mirror petals close fully (the light will also change from red (open) to green (closed)).

  4. Bring the Telescope to zenith and the rotator to a convenient position by typing:

    USER> park zenith
    USER> rotate sky 0 

  5. During winter, in case of possible snow or ice, rotate the dome to 212 degrees:

    USER> dome 212

  6. When in the TCS info screen the telescope appears as STOPPED, switch the TCS to engineering mode by typing:

    USER> eng

    The ENG/COMP push button should now be illuminated with a yellow light.

  7. On the Engineering Rack, close the dome shutter pushing LOWER MICRO until you hear a 'clunk'. Then push LOWER MAIN until the shutter stops moving. To fully close the dome shutter, push LOWER MICRO again until the shutter stops moving. If the lower shutter is open, it must be closed and lowered before the upper shutter.

  8. Turn off OIL PUMP from the engineering rack. The light will be green when oil pump is off.

  9. Fill the IDS cryostat following the same procedures as at the start of the night. Leave the telescope parked at zenith.


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28. Closing Down in a Hurry

If it starts to rain/snow, the humidity rises above 90% or the winds above 80km/h you will be forced to shut down in a hurry. If this is the case:

  1. FIRST OF ALL: Close the mirror petals

    Push and hold the MIRROR COVER CLOSE button. Check the mirror petals close fully (the light will also change from red (open) to green (closed)).

  2. Close the dome

    • Select manual control pressing the DOME SHUTRS button on the Engineering Console.

    • If the lower shutter is up, it must be lowered before closing the upper shutter:
      Push on the LOWER SHUTTER panel the LOWER MICRO button for a few seconds. Then LOWER MAIN until the lower shutter stops moving. Finally push the LOWER MICRO button again to fully lower the shutter. Keep the button pressed for approximately 10 seconds to be sure.

    • Close the upper shutter:
      On the Engineering Rack, close the dome shutter by pushing on the UPPER SHUTTER panel LOWER MICRO until you hear a 'clunk'. Then push LOWER MAIN until the shutter stops moving. To fully close the dome shutter, push LOWER MICRO again until the shutter stops moving.

    • Release the DOME SHUTRS button.

    Note: If the bottom shutter is not fully lowered, then the upper shutter will not completely seal the dome at the top and rain/wind will penetrate into the dome.

  3. Stop the current exposure and read out.

    Break out of the command and return the SYS prompt by doing, on the ICS window:

      SYS> <ctrl-z>
    Then type:
      SYS> finish
    If you were using a 'mult' command then the command finish will not stop the remaining exposures of the sequence. The sequence must be aborted with the command abort:
      SYS> abort
  4. Close the south doors if they are open.

  5. If the telescope is shut down for a long period of time then:

  6. Park the telescope using the command:
     USER> park zenith
  7. Turn off the oil pumps. Do not forget to turn them back on before you move the telescope again.

  8. Shut off the fans.

  9. If abandoning the telescope due to bad weather then:

    IMPORTANT NOTE: For safety reasons, if the observer decides to leave the INT telescope anytime during the night (between sunset and sunrise) he/she should ensure to call to the WHT telescope to inform this to the WHT TO.

    • Check/perform all the steps of the procedure Closing Down at the End of the Night.
    • Fill in a fault report with the time you filled IDS cryostat so that the Operations Team can refill it first thing in the morning.
    • If abandoning due to high humidity turn the alarm off (middle setting) to prevent it sounds during the whole night.

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29. Saving Data

Observing data can be saved either on DVD, directly to your laptop or hard-drive. You only need to write your copy disk. DVDs can be burnt on either of the two Linux public computers in the control room (INTDRPC1 and INTDRPC2).

Recording data on DVDs:

Please refer for details to the following document (also shown on the wall to the right of INTDRPC1): http://www.ing.iac.es/Astronomy/computing/recording.html.

Direct to Laptop:

Data can be transferred directly to your laptop through the INGEXT network. This can be done file by file using the scp command from your laptop:
         $> scp intguest@intdrpc1:/obsdata/inta/yyyymmdd/r{number}.fit /your/directory
Of course the * can always be used as a wildcard. Alternatively the rsync command can be used to copy all the files from the directory on intdrpc1 to a directory on your laptop. Running the command another time then updates your laptop's directory only with the new data. From your laptop type:
         $> rsync -av intobs@intdrpc1:/obsdata/inta/yyyymmdd/ /your/directory
The password can be found on the screen of the computer. For both actions intdrpc2 can also be used.

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30. Creating the Night Log

Fill in the nightlog which is accessed from the observing logger window. It is important to include the breakdown of observing time: Fill in any downtime that was encountered (bad weather, technical problems, etc.) and note the time lost. Don't forget to click "create".


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31. Filling the Operations Logbook

The printed logbook in the control room contains fields which must be filled out during the night:
CCD cryostats: Initials and local time for filling the CCD(s).
Telescope focus and reference temperature (Internal Temp in the meteorological data screen).


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32. Leaving the Building

Before leaving the building, please switch off all major lights in the control room and in the kitchen area. Check that no electrical devices are left on in the kitchen, i.e. sandwich toaster, coffee machine, etc.

IMPORTANT NOTE: For safety reasons, if the observer decides to leave the INT telescope anytime during the night (between sunset and sunrise) he/she should ensure to call to the WHT telescope to inform this to the WHT TO.



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33. Observers handover check

Ready to do it alone? Please check you are familiar with the following tasks:

  • checking the quality of your data
  • use of intercom and telephone
  • safety precautions when using liquid nitrogen
  • weather precautions, knowing when the dome must be closed
  • observing at zenith distance between 57 and 70 degrees
  • opening and closing the dome
  • moving the telescope in engineering mode
  • starting up and shutting down the observing system
  • knowing about the most common faults and how to solve them
  • writing/copying your data at the end of every night
  • filling in fault reports
  • filling in log book in control room
  • producing the observing log
  • filling in observing feedback form at the end of your run
If, after reading through this guide, the troubleshooter and the fault database, you are still having problems that you cannot solve, contact your support astronomer on the first night of your run. On subsequent nights, or if the support astronomer is unavailable, call the WHT Telescope Operator using the phone number on the whiteboard.

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34. Neutral Density Filters for Calibrations

Neutral density filters in the A&G box dedicated to the lamps.
 SYS> compfilta {position} 
 SYS> compfiltb {position} 

Where {position} is the requested filter position (0 to 7).
This moves comparison lamp filter A (B) to the position requested. Position 0 is clear, i.e. no neutral density. The command compnd can be used to change both comparison filters A and B to generate the required neutral density. The command change_agb can be used to see the names of the filters currently mounted.

For compfilta


empty (clear)

0.24
2
0.61
3
0.80
4
1.74
5
3.00
6
Opaque6
7
Opaque7


For compfiltb


empty (clear)

0.33
2
0.50
3
0.89
4
1.20
5
2.10
6
3.30
7
Opaque7

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35. Acknowledgements

Credits should be given to the INT Support Astronomers, WHT operators, ING ops-team staff and INT observers who have contributed to improve this manual along the years.

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Contact:  (IDS Instrument Specialist)
Last modified: 15 September 2021