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INT/WFC Operation Manual


  1. Introduction
  2. Areas of the telescope
  3. Safety
  4. Preliminaries
  5. Moving the telescope out of access park
  6. Moving the telescope into access park
  7. Zeroset
    1. Complete zeroset
    2. Abbreviated zeroset
  8. Initial TCS Commands
  9. Loading catalogues
  10. Pixel binning
  11. Detector windowing
  12. Readout speed
  13. Filling the cryostat
  14. Biases
  15. Opening up
  16. Flat fields
    1. Twilight sky flats
    2. Dome flats
  17. Single star calibrate
  18. Focusing the telescope
  19. Observing
    1. Acquisition
    2. Filters
    3. Guiding
    4. Dithering
    5. Exposing
    6. Observing at elevation <33 degrees
    7. Apertures
    8. Observing scripts
    9. Moving targets
    10. Examining data
  • Closing down at the end of the night
  • Closing down in a hurry
  • Saving data
  • Creating the observing log
  • Filling the logbook
  • Leaving the building
  • Observers' handover check
  • 1. Introduction

    In this guide, the following syntax will be used:
    1. The system prompts will appear in the text as type writer fonts, in the following format:
       USER> Commands to TCS (window on Telescope Control System)
        SYS> Commands to ICS after startobssys
      (Instrument Control System, pink window)
         ecl> IRAF commands
          $> Any other terminal window eg: xgterm
      Typewriter text indicates that exact command should be used. For variable input, curly braces will be used, e.g {your_input}. So, where the example might say:
        SYS> sky {time}
      to take a sky flat of length {time} seconds, at the prompt you would type:
        SYS> sky 10
      to take a sky flat of length 10 seconds.
    2. Words in green correspond to actual buttons to be pressed.
    3. Words as hyperlinks go to corresponding pictures or further details.

    2. Areas of the telescope

    The control room is located at the top floor (3rd floor) of the building, and has the following key areas:
    1. The Engineering Rack, with all manual movement controls.
    2. The Engineering Console (photo1, photo2) which contains the dome lights, engineering button lights, Emergency Stop and reset buttons, and the Computer/Engineering mode switch. There is also the TV showing the inside of the dome, and the speakers providing the sound.
    3. The ICS Screens, (Instrument Control System). A Mosaic of the various ICS windows can be seen here: ICS Windows
    4. The Meteorological Data Screen.
    5. The Whiteboard, containing lots of details and information.

    3. Safety

    1. IMPORTANT: Before starting work at the telescope please make sure you read this safety information. Please print and read safety checklist for INT visiting astronomers very carefully. If you agree with all the items, please sign it and hand it to your support astronomer.
    2. Please use a lone worker alarm and follow the lone working guidelines when you are observing alone at the INT. They can be found on the back wall of the control room, on a white rack (see this photo of the lone worker device. They are specific to each telescope so should never be taken away. The orange buttons should only be pressed in a real emergency.
    3. You must follow the instructions given to you by the support astronomer or the WHT Telescope Operator (OSA), eg. abandoning site in bad weather or regarding the operation of the telescope and instrument. They are responsible for your safety.
    4. There is a laser curtain installed in the lift that will cause the elevator to stop if the light path is broken by a person or object. If this happens you may be stuck in the elevator. Also, due to its age, the lift is not reliable. For these reasons we recommend that you don't use the elevator outside the Operations Team working hours (9:00 - 15:30), nor on weekends.

    4. Preliminaries

    1. In the control room, first check the Operations Logbook for any restrictions that may be still in force. In the upper-left corner of the Operations Logbook, write the names of all observers who will be at the telescope during the night.
    2. Turn on the dome lights (MAIN ON/OFF) from the Engineering Console and raise the control room blind.
    3. Make a visual inspection of the observing floor (and the balcony above the control room if the telescope is at access park) to check that the telescope is free to move e.g. no ladders or steps are close to the telescope or test instruments connected.
    4. Clear any emergency overrides by pressing the RESET button next to the EMERGENCY STOP button on the console. If the light does not clear, check for emergency stop buttons that may have been pressed.
    5. Turn on the OIL PUMP from the engineering rack.

      IMPORTANT: The oil pump must be switched off at the end of the night, or when the telescope has not been moved for more than an hour (e.g. during bad weather).

    6. In any browser, open the new ING Observing Log system, to see in near real time the acquired images and allow you to complete the night report at the end of the night. The section on creating the observing log tells you about how to complete the night report, and to save the night log at the end of the night.

    5. Moving the telescope out of access park

    On the engineering rack:
    1. Turn the DEC QM variable speed control fully clockwise.
    2. Turn and hold the limit key-switch clockwise in the OR (override) position following the next few steps. The limit key-switch causes the slow motion clamps to re-engage.
    3. Push the DEC QM button to go back to Quick Motion. Note that both the SM and QM lights are lit when in Slow Motion. It is in Quick Motion when only the QM light is lit.
    4. Push the DEC[-] button. This will move the telescope up and away from the balcony.
    5. When declination is below 90 degrees you may release the limit key-switch. If the audible alarm sounds, push the ACCEPT button on the Engineering Console to mute it.
    6. To bring the telescope to zenith manually continue to push the DEC[-] button and stop at DEC=28d 45' (+/- 1 degree). This needs a bit of experimenting because the telescope will not stop immediately when you release the DEC[-] button. The telescope is now at zenith.
    7. Push the DEC SM button to re-engage the slow motion clamps. When Slow Motion is activated only the SM light is lit.
    8. Alternatively, once you are out of the override limit, switch to computer mode by turning the key on the Engineering Console. In order to do this four conditions must be met:
      • There must be no alarms pending (press the RESET button next to EMERGENCY STOP on the Engineering Console to clear).
      • The oil pumps must be switched on.
      • The telescope must be out of the override limit.
      • The declination and hour angle must be in Slow Motion (DEC[SM] and HA[SM]).

      Now, type:
       USER> park zenith 
      To park the telescope at zenith.

    6. Moving the telescope into access park

    1. If the telescope has been zeroset since the last time the TCS was re-started then in Computing Mode type:
       USER> park zenith 
      There is no problem if an alarm starts to ring, just acknowledge
       USER> ack

      After the telescope stopped at Zenith, move it to the park position:

       USER> park ap1 
      If you're not sure then try typing the commands: if the telescope hasn't been zeroset it won't move.
    2. Switch to Engineering Mode by typing:
       USER> eng
    3. At the Engineering Rack, turn the DEC QM (Quick Motion) variable speed control fully clockwise, to quicken the process.
    4. In order to move to 106 degrees (access park), using your left hand, turn and hold the limit key-switch clockwise in the override position following the next few steps. The limit key-switch causes the slow motion clamps to re-engage.
    5. Push the DEC QM button to go to Quick Motion.
    6. Push and hold the DEC[+] button; the telescope will then stop at access park by itself. There is no danger in keeping the DEC[+] button pressed.
    7. Now you may release the limit key-switch.
    8. Bringing the telescope down may cause an alarm to activate as the mirror nears the vertical. Push the ACCEPT button on the Engineering Console to mute the alarm.

    Had the telescope not been zeroset since the last time the TCS was re-started then the entire procedure would have to be done in Engineering Mode:

    1. You would first switch the telescope to Engineering Mode, as in point (2) above.
    2. Using Quick Motion you would move the telescope first to zenith. At zenith the telescope should be vertical, with the HA synchro indicator pointers at the "12 o'clock" position (HA = 0h), and the DEC indicator pointers around the "9:50" position (DEC = 29d).
    3. After this, using only the DEC controls, you would bring the telescope down towards Access Park, still in Quick Motion. The telescope should end up pointing in the direction of the control room window.
    4. Only when the telescope can no longer move any further down you need to start using the override key switch, after which the procedure is as above, from point (4) onwards.

    To avoid having to do this it is easiest to park the telescope at zenith before re-starting the TCS, should you be forced to do so.

    7. Zeroset

    The "Complete zeroset" of the telescope should be done only in the afternoon of the first night of your run by the SA. It can be also executed after any TCS restart or when the pointing is poor. Remember to park zenith the telescope first. 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.

    IMPORTANT: During all runs, the "Complete zeroset" must be run only by the INT SA student astronomer on the first night. It is not necessary to zeroset the telescope by the visitor observers during any another night. Visiting observers only need to run the "Abbreviated zeroset" in order to inherit the TCS pointing model from the previous night or the INT TCS default one. If a "complete zeroset" is required for the reasons stated above, then the observers should contact the WHT OSA for help.

    IMPORTANT: Record an encoder log whenever the complete zeroset is done. The command sequence should be (in the TCS User window):
     USER> LOG ENC ON 10 
      ... Perform the complete zeroset ... 

    7.1 Complete zeroset

    1. Park the telescope at the zenith position (see section on moving the telescope out of access park), and switch to Engineering Mode using the command:
       USER> eng
    2. Check that the pointers on the Engineering Rack are on the correct sides for the zeroset, as indicated by the labels. If they are not you should move them to the correct sides using the HA[+]/[-] and DEC[+]/[-] buttons. The light above each dial will flash as the telescope moves through the zeropoint. This should be done in slow motion (SM).
    3. In the TCS User window, enter:
       USER> zeroset ha target         [or: zero ha tar]
       USER> zeroset dec target        [or: zero dec tar]
      n.b. These commands need to be typed in pair. If you type only one and then zeroset only that axis, it won't work.
    4. Using the HA[+]/[-] and DEC[+]/[-] buttons with slow motion (SM) selected and the SM variable speed control set to about half-way, move the telescope so that the synchro dial pointers move through the zeroset marks in both axes. This should be done in the same order they were typed, hour angle then declination.
    5. The TCS will beep if the zeroset is successful. The yellow LEDs mounted above the synchro dials will also briefly flash at the same time confirming that the telescope has been zeroset.
    Note: Occasionally when moving through the zeroset position the yellow LED will flash but the TCS computer does not beep to acknowledge the zeroset, or vice-versa. If this happens, finish the entire zeroset procedure. Then move the telescope back to the pre- zeroset position, and redo the zeroset.
          USER> cal def                   Loads the default TCS pointing model.
    Use on the first night of run.

    7.2 Abbreviated zeroset

    On subsequent nights of the observing run, and if the TCS has not been restarted, load the previous TCS pointing model:
          USER> cal last                  Loads the previous TCS pointing model. Should
    be used on all subsequent nights of the run.

    8. Initial TCS commands

    These should all be typed now so that the telescope is ready for the night's observing. If the focal station is not the one you expect, contact your support astronomer.
          USER> show focal                Shows the focal station setup.
          USER> focus {x}                 Sets focus to a good value,
    where x is the value shown
    in the log book and on the whiteboard.

    9. Loading catalogues

    Start by checking which objects are loaded into the TCS current list of targets.
          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, see the TCS catalogue format page for more information. They can be created with any text editor, and should be saved as {your_catalogue}.cat, with no capital letters in the filename. 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 (one or more), but no tabs, and there should be no spaces or punctuation other than an underscore in the object name. 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/  
    and then, from the instrument control system:
          SYS> cp /home/intguest/{your_catalogue}.cat /int/cat 
    The catalogue can then be included using the command:
          USER> include {your_catalogue}   
    Note that the .cat extension is not required.

    It is also possible to add and remove individual objects using the following commands:
          USER> source sn1987a 05 35 27.9 -69 16 10.00 J2000  Creates object. 
          USER> add                                             Important! Loads
    object into TCS.
          USER> remove {object_name}                            Removes object.  
          USER> out file {your_catalogue}                       Writes the contents
    of the current TCS
    catalogue to file.
    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.

    10. Pixel binning

    Binning is possible in all 4 CCDs and windowing on CCD4 only.

    WFC binning can be set with the following commands:

          SYS> bin 1 1   (1x1 pixels, no binning, by default, pixel scale=0.33") 
          SYS> bin 2 2   (2x2 pixels, pixel scale 0.66")
          SYS> bin 3 3   (3x3 pixels, pixel scale 1.0")

    Be aware that binning increases the noise by a factor of 2-5. For the last binning noise and gain values, please check the CCD Quality Control pages. The following plots show examples of binning and noise on CCD2:

    CCD2 bin 2x2 slow
    CCD2 bin 2x2 fast

    Readout times for the whole 4 CCD mosaic for different binnings and readout speeds are provided in the following table:


    11. Detector windowing

    For time resolved photometry windowing data can be a useful way to reduce readout time. Note that only chip 4 of the WFC can be windowed. The window size can be set with the command:
           SYS> window {n} "[{x1}:{x2},{y1}:{y2}]"
    To enable this window type:
           SYS> window {n} enable
    and to disable type:
           SYS> window {n} disable
    The window size and whether it's enabled can be seen on the GUI.

    NOTE: Please do not attempt to use the entire CCD4 as a window (with or without any binning option). This will crash the system.

    WFC windowing is possible only on CCD 4. To set binning window [X1:X2,Y1:Y2] (with X and Y coordinates to cover the necessary region (CCD coordinates of chip #4) around the object, type:

           SYS>  window 4 '[X1:X2,Y1:Y2]'

    where (X1,Y1) and (X2,Y2) are the physical corners of the window defined around the object. To disable this window, type:

           SYS>  window 4 disable

    For example, to define a small central 1'x1' window in CCD4, one should use:

           SYS>  window 4 '[934:1114,1960:2140]'

    To define a small central 5'x5' window in CCD4, one should use:

           SYS>  window 4 '[569:1479,1595:2505]'

    While to define a central 10'x10' window in CCD4, one should use:

           SYS>  window 4 '[168:1988,1190:3010]'

    NOTE: By defining a central window, the overscan information is lost. In order to keep the overscan, one should define the window close to the edge of the CCD4 overscan region BIASSEC='[10:2150,4105:4190]'.

    For example, to define a 1'x1' which includes the overscan, one should use:

    sys> window 4 '[934:1114,3830:4190]'

    which includes in Y both the 180-pixel window and the original overscan from Y=4105 to 4190.

    Once again, CCD4 is the only chip that can be windowed.

    Moreover, one can define four different windows at the same time on CCD4 (provided they do not overlap), namely window 1, window 2, window 3 and window 4. Remember, these are not related with the four chips.

    Regarding reading time for different size windows, we measured the following times in slow mode:

    Whole CCD4  (2154x4200 pix) - 46 sec  
    10'x10' FOV (1820x1820 pix) - 18 sec 
     5'x5'  FOV (910x910 pix)   -  6 sec 
     2'x2'  FOV (360x360 pix)   -  4 sec 
     1'x1'  FOV (180x180 pix)   -  3 sec
    NOTE: Binning and windowing at the same time will cause the system to crash.

    12. Readout speed

    Check that the readout speed being used is correct. This can be changed either from the SYS prompt using the commands:
           SYS> rspeed slow   
           SYS> rspeed fast   
    or from the GUI by pressing the 'fast' or 'slow' button. The fast readout speed is ~10s faster than the slow. However, the fast readout adds read noise to your image, so if looking at faint objects for which it is the dominant source of noise then slow readout is recommended.

    13. Filling the cryostat

    IMPORTANT: Wear safety helmet (with visor), apron and gloves when filling cryostats (photo)

    IMPORTANT: The cryostat on WFC should be filled at least every 16 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 16 hour limit. If for any reason the observer at INT cannot ensure that the cryostat will be filled within 16 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 the ING schedule.

    Please take extra care when working with dewars, particularily with the follwoing points:
    • 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 filled more than 30% should be used;
    • Ops-team fill the dewars before the weekend, so only create a fault report (FR) if both dewars are below 30% on a working day which is NOT the last working day of the week (typically Friday);
    • Users must not completely empty any Dewar;
    • The 30% full Dewar will be used in case the silicon filling tube brakes on the Dewar in use.
    • Please wait long enough (at least 5 minutes!) before removing the silicon tube (the silicon tube should NOT be frozen when it is removed, otherwise it will break).
    These are the steps to fill the cryostat:
    1. The dewars are located at the balcony, and the telescope must be in access park for this procedure (see section on moving the telescope into access park).
    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 smaller dewar can be used. Take care with the hoses as they are prone to breaking when cold.
    4. Check the pressure gauge: the pressure should be between 0.5 and 1.5 bar. Again, use the smaller dewar if this is not the case.
    5. Wheel the dewar carefully into position opposite the prime focus, with the earth wire, filler tube and pressure gauge at sensible positions.
    6. Connect the dewar to earth; use the earthing point on the hand rail to the right of the telescope.
    7. Fully insert the filler tube into the cryostat hole, going through the metal triangle, under the plastic tie.
    8. On the dewar top, check that the GREEN pressure build valve is closed. Then open the BLUE decant valve.
    9. Vapour will come out of the cryostat continuously while you are filling it. However, it is not full until liquid nitrogen is seen to be spilling out onto the floor. You will hear this as well.
    10. Close the BLUE valve.
    11. Wait a couple minutes 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.
    13. Always note down in the Operations Logbook what time the cryostat was filled and the initials of your name.
    14. The cryostat must be refilled before the start of the night's observing, and again in the morning before you leave. In the event of leaving the telescope early (e.g. due to bad weather) fill the cryostat, then fill in a fault report so that the cryostat can be filled again in the morning by the operations team.

    14. Biases

    It is recommended to take a series of biases. Follow this sequence:
    1. Turn dome lights off.
    2. Close primary mirror.
    3. As extra precaution, place a narrow-band filter if any in the wheel.
             SYS> bias                               Take a bias frame.
    4. Obtain the bias level and the readout noise in an area free of cosmetics and compare with the values recorded at WFC CCD Quality Control. Use imexamine, key 'm' in IRAF. Check also for any noise patterns, make a cut in a column and a row using 'c' and 'l' respectively using IRAF's imexamine.
    5. If happy, take a series of biases using the multbias command.
             SYS> multbias {n}                        Take {n] biases.
    6. To cancel type
             SYS> abort
    If gone for dinner, leave a note on the observer's desk about biases being obtained.

    15. Opening up

    1. Check that the weather conditions allow for observations: the humidity is below 75%, the rain sensor is "dry" (no rain), and the weather was stable for at least 20 min.
    2. Set the humidity alarm to 75%. If it's already above that level set it to 90%.
    3. Check the binning, readout speed and windowing have been set correctly.
    4. Check that the IRAF window and Observing Log are both showing the correct directory for the night you are observing.
    5. Fill in the 'Who Goes There?' window with your proposal number and the name of the PI.
    6. Open the south doors, and the double doors between these and the dome for ventilation, if humidity is below 75%. If the wind speed is >40 km/h, or you close for bad weather, the south doors will need to be shut again. It is the observer's responsibility to shut them at the end of the night.
    7. Turn off the lights in the area between the control room, the dome and the south doors, and the control room corridor.
    8. Ensure the lift (elevator) is at least one floor down and turn its lights off. Do not take the lift after 15:30 or during weekends.
    9. Take the stairs back up and turn the lights off at the far end of the control room nearest the south doors.
    10. Using the CW (clockwise) and CCW (counter-clockwise) buttons on the lower engineering rack rotate the dome so that it points east, away from the sun. This should leave the dome over the doors on the left as you look through the window. Note that there is a compass laminated onto the desk in front of the Engineering Console.
    11. Turn the dome lights off on the Engineering Console.
    12. On the Engineering Rack, in the Upper Shutter panel, use RAISE MICRO to raise the shutter slowly, until you hear a 'clunk' and the Main Overtravel light turns off.
    13. Now use RAISE MAIN to raise the upper shutter, until another 'clunk' is heard, and the shutter stops moving.
    14. To fully open the upper shutter RAISE MICRO must be used again, until the 'clunk' is heard and the shutter stops moving.
    15. Push and hold the PRIMARY MIRROR OPEN button at the engineering rack until all the petals are fully open. The telescope needs to be at or near access park in order to make sure they have opened fully.
    16. Turn the DOME VENT FAN on, on the Engineering Rack, to provide further ventilation. This should be turned off if the humidity rises above 75%.
    17. Move the telescope out of the override position (see section on moving the telescope out of access park).
    18. Close the control room blind.

    16. Flat fields

      A set of twilight sky or dome flats should be acquired at least once per run to reduce WFC images. Preferably, they should have between 20,000 and 30,000 counts illumination, which could be measured in IRAF/DS9 with imexam (by pressing "c" for column cut over the DS9 window).

    16.1 Twilight sky flats

    1. Include the blank fields catalog ("Table of 38 blank fields for sky flats" - newblank38 catalogue) using:
       USER> include newblank38   
      You can see the content of the catalogue but eitehr typing 'more /int/cat/'.
    2. Move to an appropriate star field from the catalog using:
       USER>  gocat {field name}
      The field should have its RA within 1 hour of the current sidereal time, which is shown on the TCS Display window. If possible choose a wfc or wfs field, as these were especially chosen to be blank over large areas for the wide field camera. If one is not close enough, then one of the other fields will do.
    3. Select the appropriate filter using the GUI, remembering to first use narrow filters, then broadband filters, and typically moving from blue to red within each group in the evening. In the morning this will be the opposite way around. For instance, at sunset twilight, the following order is recommended: U, V, B, Sloan g, Sloan r, and Sloan i.
    4. Use:
        SYS>   ftest 2
      to perform a two second windowed glance. This will read out almost instantly, allowing the sky levels to be determined using IRAF on the data reduction machine using:
         ecl> display s1[1] 1; imexam
      By hovering the pointer over the background and pressing m the pixel values will be displayed, for the area covered by the pointer. The ideal level for the flats is between 20,000 and 30,000 counts, though anything from 10,000 to 40,000 counts should be useful.
    5. When the background drops to an appropriate level a flat field can be taken using the command:
        SYS>   sky {time}
      with the time expressed in seconds. Times shorter than 2s or longer than 120s are not recommended for flats. Remember that with the same filter, assuming the level was good for the flat just taken and you are using slow read out mode, the exposure time will need to be increased by a factor of 1.5 to account for the dropping background brightness in the evening. In the morning, of course, the exposure will need to be decreased by a factor of 1.5.

      The sky level can now be checked in IRAF using the command:
         ecl> display r{number}[4] 1; imexam
      again, using 'm' to check the sky level. The {number} can be seen on the GUI. The fourth extension is viewed because this shows the middle CCD of the mosaic.
    6. It is customary to offset the flats taken in the same filter, so that the images can be combined to remove stars later. This can be done using the command:
        SYS>   offset arc {arcsecRA} {arcsecDEC}
      with {arcsecRA} and {arcsecDEC} being the number of arcseconds you want to offset by. Note that {arcsecRA} and {arcsecDEC} are absolute values (based on the last gocat pointing) and not relative values (not based on the last offset). Therefore a different offset will be needed for each flat in the same filter to avoid having multiple flats in the same place.
    7. When changing filters the ftest script can again be used to check the sky levels so the correct exposure time is used for the flat.

    Autoflat is an automated flat fielding script. Using the commands given below, the script takes a list of filters, prioritises them and acquires the number of flats requested. If the sky is too bright/dark for a given filter it will skip that filter and continue to check the next one. Once all flats have been taken or the sky level is out of range the script will end. A summary of the successful flat fields is printed at the end. Be aware, the script does not work with windowing or binning.

       SYS>   autoflat num_flats_per_filt rspeed f1 f2 ... fn
    where: num_flats_per_filt represent the number of flats in each filter, rspeed is the CCD readout speed (slow or fast), and f1, f2, ..., fn are the filter names for filters 1, 2, ...., n

       SYS>   autoflat 5 fast r stY stB Hbb 
    This will attempt to take 5 flat fields in fast readout speed in the filters Sloan r, Stromgren Y, Stromgren B and H-beta.

    The script does not work yet for the following filters: WFCWash51 (#223), WFCStrHbN (#225), all the NOVA filters. For these filters, flat fields shall be taken manually.

    The script can be aborted using Ctrl+C. After breaking the script, please check the binning, readout speed and windowing, as they are changed as part of the normal functioning of the script.

    The autoflat script aims to fulfill the following criteria: MAX counts: 40,000; MIN counts: 20,000; TARGET counts: 30,000; MAX exptime: 120s; MIN exptime: 1s.

    The filters are prioritised first by bandwidth into broad (B) and narrow (N), then each group of B and N are prioritsed according to central wavelength, typically blue-to-red in the afternoon and red-to-blue in the morning.

    16.2 Dome Flats

      Dome flats could be acquired if twilight flats could not be taken for some filters. For this, the dome shutter should be closed, mirror petals opened and the right filter selected.
       USER> park flat    Sends the telescope to the right position for dome flats
      The telescope should now point to hour angle 0 0 0, declination +80 0 0. Now move the dome to position 242 by typing the command:
       USER> dome 242     Sends the dome to the right position for uniform illumination
      The main dome lights must be off, and the dimmer lights should be on using the black control located to the right as you leave the control room to the dome. The knob of the dimmer lights should be turned somewhere at 2/3 or full position (100%). In the WFC Dome Flat Assistant we give a table for some guides about exposure times to be used with the WFC and different filters.
             SYS> flat {time}                        Take a dome flat of {time} seconds.
             SYS> multflat {n} {time}                Take {n} dome flats of {time} seconds.

    17. Single star calibrate

    On the first night, the default pointing model should have been loaded in the initial TCS commands, and it is likely to be accurate. However, it is good to check it and make an additional correction with the following procedure.

    First, check the lower shutter which should be in the low (default) position and point to a bright star (you can use one from the system catalogue.

    SYS> agwin acq pos 1032 512Sets readout to the centre of the autoguider chip.
    SYS> autotv onTurns on continuous readout mode.

    On the autoguider window mark a cross in its centre by selecting TOGGLE CENTRE CROSS from the SETUP menu.

    USER> enter aperture 0 1065 -42Changes the telescope pointing to the autoguider centre by redifining aperture 0.
    USER> cal faintSends the telescope to a suitable calibrate star.

    When the HANDSET menu is enabled on the TCS window, then type <ctrl-z> on the TCS window to break out of it.

    If the star appears right on the cross-hairs then the pointing is okay, and the rest of this section can be skipped. Otherwise, press the HANDSET button (INSERT key of the keyboard) to centre the star on the cross-hairs in the centre of the autoguider window. Use the arrow keys on the keyboard to move the telescope.

    IMPORTANT: In case no star is visible in the autoguider window, check on the GUI if the camera shutter is open. Follow instruction about no stars seen in the autoguider window section of the troubleshooter.

    Please note:

    1. Given the orientation on sky of the autoguider field of view, arrows move the telescope in a way that can get the observer confused. So lower the moving increment rate on the TCS window to the lowest value and do a test first. Think of it as moving the centre cross to the star, and not the star to the centre cross.
    2. Pressing an arrow key once moves the star by the increment size value shown on the TCS window, near the top. The increment can be changed by using the '<' and '>' keys.
    3. After pressing a key, wait until the autoguider window has refreshed showing the new position.
    4. In case the star is either too faint or saturated, then the exposure time can be changed by going to SELECT -> INTEGRATION TIME -> SELECT FROM MENU. If still saturating, considering using a narrowband filter, if there is any on the filter wheel.
    Once the star is well centred, press HANDSET and type:
          USER> point calibrate           Writes the new pointing model to file.  
          USER> cal anal zero             Loads the new pointing model 
    The rms of this solution is typically 0.01, because only one star is being used. Type 'Y ' to accept.

    Prepare the telescope pointing back to the centre of chip 4:
           USER> enter aperture 0 -251 326
           SYS> autotv off                Turns off continuous readout mode. 
    IMPORTANT: If the pointing is still bad after the single star calibrate, then refer to bad pointing section in the troubleshooting guide. guide. First try zerosetting the telescope again, the default calibrate and then the 7 star calibrate if necessary.

    18. Focusing the Telescope

    The typical "default" WFC focus is around 43.35 and the last night value is written on the white board. If the seeing is unstable (changing rapidly) or bad (> ∼2 arcsec) do not attempt to focus the telescope. Instead, you can adopt the focus from the last night. If you need to determine focus values in more filters, use preferably broad band filters first, which need lower exposure times, and afterwards narrow band filters, if sky conditions are stable. Otherwise you could rely on filter offsets if they are known in the filter database. Focusing in narrow band filters needs longer exposure times (at least 2-3 times or more) than in broad band filters.

    To determine the best telescope focus select a suitable field (e.g. one of the WFC photometric standard fields, check visibility using LANDSCAPE). Choose either a field close to your first target, or continue using the same field as the single star calibrate. Sometimes these fields can be too crowded and in that case try a suitable blank field.
       SYS> gocat {suitable standard field}  
    Then make sure the camera is not binned or windowed (disable any eventual defined window),
       SYS> window 4 disable
    and run the focus script.
        SYS> focusrun &  
    IMPORTANT: If you are focusing on one only filter, then run the focus run in a suitable filter. A broad-band red filter is desirable since it will have the best FWHM for a point source.

    IMPORTANT: After the fucusrun, it is important to check that the detector configuration was correctly restored and it is recommended to take a glance to confirm.

    A dialog box will pop up and the appropriate values may be filled in and a focus run started. The default values should be good, but the recommended values are:
    Number of exposures (n)      =        9 
    Focus start value            =        0.2mm below last known focus (see white board)
    Step size                    =        0.05 mm 
    Exposure separation          =        10 arcsec 
    Exposure time                =        15 sec 
    1. Hit RUN. All n exposures will be taken on the same frame, giving lines of repeated stars. There is a double space between the first and second exposures to make them easily identified.
    2. Accept any error box messages and close the focus run window.
    3. Load the IRAF package wfc_ql, if not already loaded:
         ecl> wfc_ql
    4. Next, type:
         ecl> wfc_starfocus
      to compute the best focus value from the focus run. It will ask you which run number the focus run is, and the number can be found on the GUI. It will know all the values you selected for the run.
    5. It will ask you to identify as many first stars as you want, 10-12 being typical. This is done by placing the cursor over the first star of a set (the star image more distance in a row of exposures) and hitting 'm'. Make sure that the whole line of stars is on the CCD, and that the stars you pick are clear single stars and not obscured or saturated. Pressing 'q' when finished produces a graph showing what it believes to be the best focus value. Quit display window with 'q' before closing it.
    6. Set the best focus value at the end of the focus run using the command:
            USER> focus {value}
      If the target is needed back at the original position then the gocat command will need to be repeated.
    7. Enter the value obtained on the whiteboard and in the log book.
    8. If, after running the focus script, the stars are still very unfocussed or doughnut-like instead of point-like, then the focus run can be done again using a larger step size and more steps as appropriate. A 0.1mm step size with 11 steps may be a good next try.

      19. Observing

      This section acts as a glossary of standard commands, but is organised into progressions of tasks and order of use.

      19.1 Acquisition

      Loading catalogues and objects is described in the section Loading Catalogues. To move to one of these objects:
             SYS> gocat {object}            Telescope will slew to that object,
      which must be loaded into the TCS,
      and track it, e.g.
             SYS> gocat 92-248              Moves the telescope to the Landolt field
      92-248 which is stored in the system catalog.

      19.2 Filters

             SYS> filter {filter}           Changes filter. Use the same acronym
      as seen in the GUI wheel, e.g. Ha, r.
      Alternatively, just click on the filter
      wanted in the GUI.
      A de-focus term will automatically be applied when you change filter. It can take a few seconds to finish changing focus, and this can be seen on the TCS information screen.

      19.3 Guiding

      IMPORTANT: it is strongly recommended to use guiding for exposures longer than two minutes.

      Check that the autoguider tv-mode is off. If it is on, type:

             SYS> autotv off
      When the gocat command has been executed to slew to a new field then a list of guide stars will appear in the Talker window. This list can also be seen by entering:
             SYS> more /tmp/gsc.out
      If this does not occur then check that the auto predict is on (see section on finding guide stars in the troubleshooter).

      The guide window size can be set in the GUI under the SETTINGS tab. A size of 120x120 pixels (resulting in a sky field 45"x45") is recommended.

      A guide star of appropriate magnitude should be selected from this list. To guide on this star use the command:
             SYS> guide on pixel {x} {y}
      with {x} and {y} being the same values as before. If the guide star doesn't appear within the window you can try a larger window size (for instance 180x180 pixels under "Settings" on the GUI) or do the following:
             SYS> guide off
             SYS> agwin acq pos {x} {y}
             SYS> field
      This centres the AG on the position where the guide star should be and searches for potential guide stars within that field displayed. They will be marked and numbered on the autoguider. Sometimes this command needs to be issued twice before it works.

      To guide on one of these stars, use the command
             SYS> guide on star {n}
      where {n} will be a number assigned to each star, being 1 the brightest. Be aware that the field command often picks up artifacts, so you should always check that you are guiding on a real object. For this reason it is recommended not to use scripts for setting up guiding.

      It usually takes some time to turn the guiding off (SYS> guide off). If it takes too long, then use <ctrl-c> to exit it, then check guide job ID number and kill this process:
             SYS> autotv off
             SYS> jobs
             SYS> kill -9 %n
      where {n} is the job number (not the PID!). The command to turn the guiding back on is:
             SYS> guide on

      Before starting the exposure it's important to leave the autoguider to settle. When guiding, the TCS will display A/G on rather than tracking, and show the x and y errors in the guiding. These should be allowed to drop below 0.3, though if the seeing is bad the errors may not get lower than 0.5. It can take a few readout cycles for the errors to be displayed in the TCS. If you do not see them then the guiding is not working.

      IMPORTANT: After setting a new exposure time for the autoguider, you should close the popup window with the buttons provided and NOT the X button (at top right of the window), since doing the latter prevents display of the popup again.

      IMPORTANT: When using long autoguider integration times, then increase the wfc_ag_sequencer time before readout to be integration time + 9s.

      The aim of the so-called "autoguider sequencer" (the wfc_ag_sequencer program) is to avoid extra noise (interference) on science images if they are read out while autoguider is reading out. The following two cases are possible:

      Observing programs using guiding (exposure times longer than 2-3 min), the sequencer must be always used, so the sequencer should remain active (red flag checked) during the whole run. Also note that any TCS restart will start the observing system with the sequencer active by default.

      When observing guiding for time-series measurements, it is best to change the command in the sequencer to "guide on pixel {x} {y}" where {x} and {y} are the coordinates given when starting the guider. This will help minimise drifts between exposures.

      Observing programs not using guiding (only tracking) for their short science exposures (less than 2-3 min) should un-mark the sequencer by pressing in the small window on red click button (un-press it) to dis-activate. Also, observers should un-mark this option after each TCS restart.

      Moreover you want to turn off the autoguiding. This can be done using the command:

             SYS> guide off
      By default in guiding mode, the sequencer stops autoguiding 10s before the WFC science image readout, in order to avoid this noise, but you can change this value (thought, it should not be less than 8s). If you do not need guiding for your science, then you should stop the autoguiding and sequencer using the above two actions, or using the following sequence commands:
             SYS> guide off 
             SYS> jobs 
      then look for which job is connected with wfc_ag_sequencer, and type:
             SYS> kill -9 %n 
      where {n} is the corresponding job number. If you decide to guide later because you are doing longer exposures, if the sequencer GUI is not on screen then it can be started using the command:
             SYS> wfc_ag_sequencer & 

      19.4 Dithering

      Dithering can be done in several ways, and which is most useful will depend on whether you are guiding or not, and the size of the offsets.

      Offsets can always be applied using the command:
             SYS> offset arc {arcsecRA} {arcsecDEC}
      Note that the {arcsecRA} and {arcsecDEC} offset shifts are in the RA and DEC directions, expressed in arcseconds. The offsets are relative to the telescope catalogue pointing (the pointing provided by the gocat command), and hence, if you keep issuing the same offset, then the telescope will not move.

      If you're not using guiding this will be the easiest way to perform all your offsets. If you are, however, then complications can arise, because guiding must always be turned off before using the offset command, otherwise the guiding will move the telescope back to its original position.

      If you're guiding and making offsets small enough to keep the star within the field of the autoguider, then the field command may be used to locate it once again:
             SYS> guide off
             SYS> offset arc {arcsecRA} {arcsecDEC}
             SYS> field
             SYS> guide on star {n}
      Where {n} is the number assigned to your guide star.

      If your dither positions extend over a range >1 arcmin then you will probably find the guide star moving out of the field. In this case the easiest thing to do is calculate multiple dither positions for the object you're looking at beforehand, and then load them from a catalogue. Doing this allows you to gocat to each new position, and when the gocat command is used new positions for the guide star will automatically be calculated. There is a tool on the NASA Extra-Galactic Database (NED) to help you convert offsets into RA and Dec.

      Then use the commands:
             SYS> guide off
            USER> gocat {new_dither_position}
             SYS> more /tmp/gsc.out                  Find suitable guide star.
             SYS> guide on pixel {x} {y}
      Remember to let the guiding settle before starting your exposure, so that the errors shown on the TCS display are <0.3.

      Please note that if you want to mosaic images using all four chips then, because of the chip gaps, you will need to offset by at least 30 arcseconds in both x and y. This is due to the layout of the chip, which can be seen here: offsetting in just x or y merely causes you to move along the gaps.

      There are some dithering scripts WFCdithtrack and WFCdithguide for a 2-point, 4-point and 9-point pattern in either tracking or guiding. The script WFCdithguide is capable for both small dither offsets (max half guiding window, by default 10") and larger offsets (larger than half guiding window, but having longer overhead time).

             SYS> WFCdithtrack
             SYS> WFCdithguide

      The scripts will ask for the necessary parameters.

      Should you have any questions about dithering please direct them to your Support Astronomer, preferably in advance of your run.

      19.5 Exposing

      IMPORTANT: Before taking any sky exposure, make sure the dome has finished rotation to the new target, checking in the TCS Display window that the DOME label is not flashing!
             SYS> glance {time}                      Take a glance of {time} seconds. 
      Stored as s1.fits always, ie. it will overwrite former glances. Use it to check you're on the right field or to estimate exposure times before the actual run.
             SYS> run {time} {"comments"}            Take an exposure of {time} seconds
      with the {"comments"} added to the
      header of the fits file.
      For multiple biases, flats, skyflats, runs or glances, simply prefix the command with 'mult' and put the number desired directly after the command, e.g.
             SYS> multrun {n} {time} {"comments"}    Take {n} exposures of {time}
      seconds, adding the {"comments"}
      to the files' headers.

      There are three ways to interrupt a running exposure. Type

             SYS> <Ctrl>-z

      to get the prompt back 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, and other runs in the sequence carry on. So for ending a multrun exposure you need the command abort instead.
             SYS> finish

      The command newtime modifies 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 and the last exposure is saved to disk.
             SYS> newtime {new-exposure-time}

      If you are running a script, you need to type:
             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.

      19.6 Observing at elevation <33 degrees

      Remember that the lower shutter starts to vignette at telescope elevation lower than 33 degrees. So if you wish to observe at a zenith distance between 57 deg and 70 deg, or elevation 33 deg and 20 deg respectively, then you need to raise the lower shutter.

      The system does not warn you so you will have to check the zenith distance (ZD) on the TCS window from time to time. Also be aware of the INT pointing limits.

      If you need to observe at elevation <33 deg then the lower dome shutter must be raised. Follow these instructions:

      The lower shutter is raised in the same way as the upper shutter, using the respective buttons in the engineering rack, in the section labelled 'LOWER SHUTTER'. Press RAISE MICRO and then RAISE MAIN. RAISE MICRO can then be used again to raise the lower shutter to the top.

      IMPORTANT: You must close the mirror petals anytime you move any dome shutters. Remember to open the mirror petals afterwards.

      Consider if opening the lower shutter is essential. Opening up takes around 10 minutes and the image quality will decrease due to observing through higher air mass. Furthermore, as the lower shutter is very large, it blocks a large fraction above preventing observations at higher elevations.

      IMPORTANT: Remember to bring the lower shutter down afterwards, as you will not be able to observe above 34 degrees elevation if it is left in the raised position.

      19.7 Apertures

      With a gocat command the telescope is sent to the RA and DEC specified for the object, so that this object appears in the middle of the centre chip (CCD 4). Occasionally, it may be desirable to centre the object in a different position, and for this apertures can be used.

      Aperture 0 is an absolute measurement and sets the centre, from which point all other apertures will be measured. This is the default pointing for the telescope and it is set at the center of CCD4, or -251" 326" from the optical axis (rotator center). All other apertures have values relative to that aperture 0. Apertures 1-5 point to the middle of chips 1-5 (where 5 is the autoguider). This means that aperture 4 is defined as 0 0.

      To see a list showing the different apertures set, use the command:
            USER> show apertures
      ap 0 -251 326 nominal aperture, object centred on CCD#4
      ap 1 704 5 centre object on CCD#1
      ap 2 357 -1043 centre object on CCD#2
      ap 3 -701 -10 centre object on CCD#3
      ap 4 0 0 nominal aperture, object in centre of mosaic camera
            (shifted from centre of CCD#4)
      ap 5 1316 -368 centre object on AG-CCD (X=1032, Y=512)
      ap 6 251 -326 centre object on RC (rotator centre)

      If, for example, you wanted to have the object you're pointing at to appear in the centre of chip 1, then simply gocat to that object and then type:
            USER> aperture 1
      This pointing will only be used for one command before reverting to its default pointing, so the aperture command should only be issued just before you want to use it.

      If it's necessary to reset the pointing of the telescope for more than one target, and you don't want to keep re-typing the aperture command, then it is possible to redefine aperture 0 so that it has this new value as the default pointing. Extreme care should be taken when doing this, however, to return the telescope to its normal pointing afterwards. Also note that when this is done apertures 1-5 will no longer point to the centre of chips 1-5, since those values are set relative to aperture 0.

      The command for doing this is:
            USER> enter aperture 0 {x"} {y"}
      In general, this should only be necessary if a seven star calibration has to be performed, and this procedure is explained in detail in the Troubleshooting Guide.

      19.8 Observing scripts

      Observers can use their own observing scripts to observe an object previously uploaded to the catalog using standard observing commands (example of guiding with small dithering is provided here: wfcsamplescript).

      What follows it's an example of how to save a script to /home/intobs/:
            sftp intobs@intdrpc1
            sftp> cd /home/intobs
            sftp> put <your_script>
            sftp> chmod 555 <your_script>
      Finally, from the INT ICS terminal in the same /home/intobs/ directory, you can run the script by this simple invocation:
            SYS> johnscript

      19.9 Moving targets

      Moving targets (such as asteroids, comets or planetary satellites) could be observed with the INT in both tracking or guiding modes using non-sidereal (differential) telescope moving rates.

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

          diff_RA = ΔRA/dt in SECONDS/sec 
          diff_Dec = ΔDec/dt in ARCSECONDS/sec 

      For instance, if rates are provided as

          diff_RA' in ARCSECONDS/hour 
          diff_Dec' in ARCSECONDS/hour

      Then the following transformations are needed:

          diff_RA = diff_RA' / (3600 x 15 x cos(Dec)) 
          diff_Dec = diff_Dec' / 3600
      In case ephemeris are provided as "coordinate motions" or "sky motions", choose the former so you don't have to divide diff_RA' by cos(Dec).

      The differential tracking rates are then input to the TCS using the following sequence of commands:
       USER> gocat {object name}
       USER> diff_rates diff_RA diff_Dec
       USER> next
      To return to sidereal tracking (e.g. for standards) issue the TCS command:
       USER> diff_rates 0 0
      IMPORTANT: The science exposure time when using guiding at differential rate is limited by the object's differential tracking and the maximum WFC available autoguider window size (recommended below 120x120 pixels, namely 40" box size).

      19.10 Examining data

      The standard way to examine the data is with IRAF on the INTDRPC1. If IRAF is not already running, then type iraf on a terminal window. This will open an xgterm window, a DS9 window and execute IRAF automatically.

      The data being collected will be stored in the directory shown on the GUI, usually /obsdata/inta/yyyymmdd with the last directory being the date on which the night starts.

      IMPORTANT: Data can be looked at in the /obsdata directory but not reduced, and must also never be moved or deleted. If you plan to reduce the data on that machine then it should be copied to a /scratch directory, in which you can make your own directory, as an exmaple /scratch/intdrpc1/<your_name>.

      Data can be displayed on DS9 using the command:
              ecl> display r{number}[4] 1
      This loads the contents of extension 4, corresponding to CCD4, of image r{number}.fits to the DS9 display. The {number} for the exposure is found on the GUI, or in the night log. If the exposure was windowed then the image will be written into extension 1. If a glance was taken instead of a run, bias, or flat then the image will have been written to file s1.fits and it will overwrite it everytime a new glance is taken.

      The image can then be examined using the imexam task:
              ecl> imexam
      Useful imexam keys include:

      v vector cut; click twice
      c column cut
      l line cut
      e elliptical plot
      s surface plot
      a text statistics
      m pixel statistics on section around cursor
      r radial profile
      q quit imexam

      These imexam keys are listed somewhere on the desk.

      Alternatively, the display and imexam tasks can be combined in one line by using a semi-colon:

              ecl> display r{number}[4] 1; imexam
      Or abbreviated as:
              ecl> displ r{number}[4] 1; imexam
      IMPORTANT: To match the standard sky orientation North up, East left, in DS9 one should rotate CCD1, CCD3 or CCD4 images by 270 deg (on DS9 Zoom/270 at the top menu), while CCD2 should be rotated by 180 deg (on DS9 select Zoom/180 at the top menu).

      If you want to display all 4 different buffers (corresponding to the four CCDs) at once, then this can be done using the command wfc_display from the IRAF package wfc:
              ecl> wfc_ql
              ecl> wfc_display r{number}
      The 'tile' option must be selected under frame tab on DS9. Note that the IRAF package 'wfc' is loaded only once, no need to load it everytime you issue wfc_display.

      An example of finding chart server to identify the CCD4 field is DSS STScI. Enter the RA and Dec corresponding to the INT pointing, set height=11, width=22, file format GIF, and retrieve image. The resulting star chart should match exactly the WFC CCD4 (as displayed in B/W and rotated 270 degrees in DS9).

      Use the following command to ring a bell sound after finishing an exposure, for example:

              SYS> run 20; talkerBellINT

      20. Closing down at the end of the night

      1. If running, stop the autoguider:
          SYS> guide off
        The sequencer should also be turned off by depressing the enable button on its GUI.
      2. Bring the telescope close to access park by typing:
         USER> park zenith
        followed by:
         USER> park ap1
      3. Push and hold the PRIMARY MIRROR CLOSE button. Check the mirror petals fully close (petals can be seen moving through a gap in the telescope structure).
      4. Push the DOME VENT FAN STOP button to turn off dome fans, if on. The red light will go on when the fans are stopped.
      5. In case of ice or snow conditions, move the dome shutter to the South

        USER> dome 212

        so ice can melt by solar heat.

      6. Once the telescope is 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. If lower shutter has been raised close the shutter using LOWER MICRO, then LOWER MAIN, then LOWER MICRO until you hear a 'clunk' at each step.
      8. Close the upper dome shutter pushing LOWER MICRO until you hear the 'clunk', then LOWER MAIN until the shutter stops moving, and makes a 'clunk'. To finish closing, press LOWER MICRO until the shutter stops moving.
      9. Bring the telescope fully down into access park (see Moving the Telescope into Access Park).
      10. Turn off the OIL PUMP from the engineering rack. The light will show green.
      11. Close the South doors if they have been opened.
      12. Fill the WFC cryostat following the same procedures as at the start of the night, and leave the telescope at access park.

      21. Closing down in a hurry

      If it suddenly starts to rain or snow, the humidity rises above 90% or the wind speed is above 80km/h, you will be forced to shut down in a hurry. If this is the case:
      1. Stop the current exposure and read out:
          SYS> <Ctrl>-z
          SYS> finish
      2. Close the mirror petals.
      3. Park the telescope using the command:
         USER> park ap1
      4. While the telescope is moving hit the DOME SHUTRS button next to the Engineering Console, so the dome shutters can now be moved at the same time as the telescope.
      5. Close the dome (as in the section Closing down at the End of the Night), remembering to close the lower shutter before the upper if it was raisen.
      6. Shut the fans off, if on.
      7. Close the South doors, if open.
      8. If you were using a 'mult' command then typing finish will not stop the remaining exposures from being taken, and the run must be aborted. This can be done by typing 'abort':
          SYS> <Ctrl>-z
          SYS> abort
      9. Release the DOME SHUTRS button on the Engineering Console for the dome shutters. If you forget to do this the dome will not track with the telescope next time the telesope is in operation.
      10. Visually check that the telescope has returned to ap1 correctly without twisting. If it has not, then issue the commands:
         USER> park zenith
        followed by:
         USER> park ap1
      11. If shut down for a long period of time then turn off the oil pumps. Do not forget to turn them back on before you move the telescope again.
      12. If abandoning the telescope due to bad weather then fill the cryostat before leaving, and fill out a fault report including the time so the Operations Team can refill it first thing in the morning. Note that only time lost due for technical reasons should be included in the fault report.
      13. If abandoning due to high humidity turn the alarm off (middle setting) to stop it going off all night.

      22. Saving data

      You can save your data directly to your laptop, an external USB device or ftp. Please refer to Transferring and Recording Observational Data for details.

      23. Creating the observing log

      Fill in the night report (even if the weather was bad and you could not observe!) by selecting 'night report' which is situated in the observing logger window on the ICS monitor. Fill out all fields, and when done hit 'create log'. A copy called is put in the observation directory so you can copy it when copying your data, and there is an option to email it to a comma-separated list of addresses. Please contact your support astronomer for copies of your log if you forget to do the above.

      Since June 2022, the new ING Observing Log web-based night logging system must be used to enter and show any night reports. Go to, which should load by default the current INT night form - otherwise, please type for example, and change the date 20221110 accordingly.

      The web log loads all the images in near real time (including the ones most recently taken). At the end of the night, if you scroll down the page to the end, you will see the button End-Of-Night Report (leave active or eventually change to INT under the other button Choose telescope), which must be pressed to get displayed the Night Report form, able for completion. Please complete all fields there, then scroll down the page at the bottom, and then press the two buttons Save to database and Save to /home/lplogs!

      24. Filling in the log book

      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 cryostat.

      - Breakdown of observing time: fill in any down-time that was encountered (bad weather, technical problems, etc.) and note the time lost.

      - The last focus used during the night. This can be found next to focus on the TCS display.

      25. Leaving the building

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

      26. Observers' handover check

      Ready to go it alone? Please check you are familiar with the following tasks:
      1. Use of telephone: numbers on right edge of whiteboard.
      2. Safety precautions when using liquid nitrogen.
      3. Weather precautions, knowing when the dome must be closed (also on whiteboard).
      4. Observing at zenith distance between 57 and 70 degrees (see troubleshooter).
      5. Opening and closing the dome.
      6. Moving the telescope in engineering mode.
      7. Starting up and shutting down the observing system.
      8. Knowing about the most common faults and how to solve them.
      9. Writing your data to an external hard drive or dvd at the end of every night.
      10. Filling in fault reports.
      11. Filling in the log book in control room.
      12. Producing the observing log.
      13. Filling in the observing feedback form at the end of your run.
      If, after reading through this guide and the Troubleshooter, you are still having problems you cannot solve then you can ring the WHT OSA. Numbers are found on the whiteboard.

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    Contact:  (WFC Instrument Specialist)
    Last modified: 01 April 2024