If this is not the case or something goes wrong with the system ask the TO, the SA or the DE.  (Instructions for starting up and shutting down the observing system can be found here.)

If you plan to reduce your data on the fly please consider that you can't work with the images stored in the /obsdata directory. You can create a directory in the /scratch filesystem (e.g. /scratch/whta/20040110) and copy the images there to proceed.

    TO> bfold 0      (to observe in the red arm only, dichroic and mirror out of the beam)
    TO> bfold 1      (to observe in the blue arm only, mirror in the beam)
    TO> bfold 2        (to observe in both arms simultaneously, dichroic in the beam)

- Set the gratings to the correct central wavelengths as in the following example

    TO> cenwave blue 4500          (sets the central wavelength in the blue arm to 4500 Å)
    TO> cenwave red 6500              (sets the central wavelength in the red arm to 6500 Å)

- Select the slit width

    TO> slitarc 1.0    (sets slit width to 1.0 arcseconds.  Maximum possible width is 22.0 arcseconds.)

- Select the dekker mask. Note that the long slit module of ISIS has a slit length of 4.0 arcminutes.

Whilst observing a dekker slide is normally inserted above the slit to mask off the slit ends.  This reduces ghosting in ISIS and it is therefore recommended that the dekker is used. To check if the dekker is in place ask your support astronomer or, looking at the mimic display, check that the dekker status CLEAR and not OUT.    If the dekker is OUT you may move the dekker slide into the beam at the correct position using the command

    TO> dekker 8

- Introduce a blue blocking filter in the red arm of ISIS. Your support astronomer will advise if one is needed to prevent contamination of the red spectrum by second order light.  The status of below slit filter slides which contain these filters can be checked on the mimic display.

    TO> rfilta 3  (introduce the GG495 blocking filter)

- Select slit mode to observe (remove the comparison mirror in case it is in)

    TO> agslit

- Select comparison mode to take lamps (introduce a mirror in the beam to drive the light from the lamps into the spectrograph)

    TO> agcomp

3.2  Controlling ISIS mechanisms from the GUI

In addition to the control of ISIS mechanisms from the WHTICS console command, there is a GUI that also allows to control them. Manuals of the new ISIS Control System and the A&G Control System that explain how to use the GUIs can be found here and here.

The use of the GUI is very simple, A number of icons buttons are used throughout the GUI in order to perform specific tasks.

The GUI has several windows, the relevant for the ISIS user is here

Back to the top

• Data acquisition commands
  Some of the most important commands related to data acquisition are listed below (arguments are denoted by <>):
  • run <camera> <int time> <"title">
    Takes a run and saves it in: rxxxxxx.fit.
    E.g. run blue 600 "N157 B", takes a 600s exposure with the blue arm and store it in the output file (e.g. r240976.fit). The title of the fits file is set to "N157 B".

  • multrun <camera> <m> <int time> <"title">
    Same as run but repeats the run sequence m times and generates m output files.

  • flat <camera> <int time> <"title">
    Takes a run and set the OBSTYPE header parameter to FLAT.

  • multflat <camera> <m> <int time> <"title">
    Same as flat but repeats the run sequence m times and generates m output files.

  • arc <camera> <int time> <"title">
    Takes a run and set the OBSTYPE header parameter to ARC.

  • multarc <camera> <m> <int time> <"title">
    Same as arc but repeats the run sequence m times and generates m output files.

  • bias <camera> <"title">
    Takes a run and set the OBSTYPE header parameter to BIAS.

  • multbias <camera> <m>  <"title">
    Same as run but repeats the bias sequence m times and generates m output files.

  • glance <camera> <int time>
    Takes an exposure and saves it in s1.fit. This file is overwritten when a new glance is taken.

  • scratch <camera> <k> < int time> <"title">
    Takes a run and saves it in: sk.fit.k is an integer within the range 1-99. The scratch file sk.fit is overwritten when a new scratch<k> is taken.

  • abort <camera>
    Abort an exposure. The data is not saved to disk.

  • finish <camera>
    Terminates an exposure and save the data to disk.

  • newtime <camera> <int time>
    Change the length of an exposure (e.g. newtime 900)

  The arguments above stand for

     < camera>    Indicates which CCD you want to use, the red or blue ones. Enter red or blue.

     < int time>    Integration time in seconds.

     < "title">        Title of the exposure recorded in the image header (optional argument).

Back to the top

5.1 Setting the CCDs from the observing system (WHTICS)

Before starting the calibration images in the afternoon you should have to set the redout speed and the windowing of the CCD camera.

- Set the detector readout speed to slow or fast (as desired) by typing for example:

    TO> rspeed <camera> slow

Have a look at the blue and red for details on the operational characteristics for each readout speed.  Normal observations are usually done using the slow readout speed. Be careful as the default velocity is fast and you have to set to slow before starting to take your calibrations in the afternoon.

- Windowing the CCDs. Note that the ISIS detectors cover more than 4 arcminutes in the spatial direction. It is therefore necessary to window each CCD to an appropriate length by defining an effective slit length. 

    TO> window red 1 "[585:1550,1:4200]"   (3.5 arcminutes for red arm+REDPLUS)

    TO> window blue 1 "[585:1550,1:4200]"   (3.2 arcminutes for blue arm+EEV12).

- Binning the CCDs.

    TO> bin red 1 2   will bin x1 in the spatial direction and x2 in the dispersion direction.

Once the CCD windows have been defined, the system will automatically create and save two files, one for each CCD, which contain the window, bin and readout speed parameters. The default file names are udas_REDPLUS.cfg and udas_EEV12.cfg. Different names can be used with:

    TO> saveccd <camera> <filename>

To load the CCD parameters use:

    TO> setccd <camera> <filename>

To load the default CCD configuration files just omit the field <filename>.

Please bear in mind that other useful data as both collimator focuses are not saved. The setccd command is especially useful after issuing a dasreset. This command resets the software and hardware of a CCD camera (e.g. when one camera stops working):

    TO> dasreset <camera>

After a dasreset the bin, window and readout speed data of the reset camera will be lost.

5.2 Taking arcs

    TO> agcomp

    TO> complamps cuar+cune

and take a test exposure:

    TO> arc red 5 test

This exposure will allow you to compute the exposure time to obtain a reasonable intense arc and to define the CCD window such that no dekker vignetting is seen. The same procedure with the blue arm. Take into account that usually long exposure times are needed in the blue.

5.3 Taking lamp flats

Before taking flats turn off all the dome lights and close the courtains in the control room.

    TO> agcomp

    TO> complamps w

and take a test exposure:

    TO> flat red 1 test

This exposure will allow you to compute the exposure time to obtain a reasonable intense flat. Flats should not be brighter than 42000 ADUs. DO NOT MAKE exposures shorter than 1 s. When using low resolution gratings in the red arm, the use of a neutral density filter is needed. ND filters can be put in place with e.g.

    TO> compnd 0.8   (to remove the ND filters just do   TO> compnd 0)

Once the proper neutral density filter and exposure time is set, do a multflat:

    TO> multflat red 11 5 "good flat"&

5.4 Taking bias

Before taking bias turn off all the dome lights and close the courtains in the control room.

    TO> agcomp

    TO> complamps off

    TO> multbias red 11&

    TO> multbias blue 11&

5.5 Taking sky flats

In case you need sky flat you should fo them in twilight. Ask the TO to open the telescope and point it to a blanck field and do

    TO> agslit

and take a test exposure to decide the exposure time:

    TO> sky red 1 test

Note that the sky brightness varies very fast and you will probably have to change your exposure time between exposures.

Back to the top

6.1 Focusing the telescope

To focus the telescope point to a bright star (V=9-10, it can be one of your standards) and open the slit to 8 arcsecs

    TO>slitarc 8.0

In this way the profile of the spectrum will be defined by the seeing not by the slit. Take an image with one of the arms

    TO>agslit

    TO>run red 5 test &

Look at the image to check if the level of counts is correct and execute

   TO>focusrun <camera> <num_exposures> <exp_time><start_position> <focus_increment>

Typical values are

   TO>focusrun red 9 5 97.7 0.05

This will take 9 images of 5s exp. time changing the focus of the telescope between images starting with focus 97.7 and incrementing by 0.05 the focus value before every image. All images are saved and you can determine the best focus by analyzing the spectral profile of them. Once the value of the focus is determined (e.g. 97.85) set the value of the focus by

   TO> focus 97.85

6.2 Taking spectra of an object

First select the slit mode and slit width 

   TO> slitarc 1.0

   TO> agslit

Ask the TO to point to the object (you can give him in advance an object list with the coordinates of the objects you plan to observe during your run). Also tell him the Position Angle you want for the slit. The TO will take an image of the slit with the TV camera and will use it to center your object in slit. If your objects are faint (V>20) it is a good practice to center a brighter object in the field close to the target and do offsets. In this case compute the astrometric offsets in advance to save time. Once your object is in the slit do

   TO> run red <exp_time> "<comment>" &

   TO> run blue <exp_time> "<comments>"&

6.3 Night calibrations

If you need arcs of lamp flats during the night proceed as in #5.

6.4 Observing bright targets

If you need to observe bright targets you can use the main neutral density filters in the light path, common for both red and blue arm. Take into account that these neutral density filters are not uniform, mostly outside the useful area of the chip. The table below indicates the area of the chip in pixels where the filters were observed to be "gray". In addition to the non-uniformity all these filters have small-scale structures, difficult to be removed by flat-field correction. If there is a need to use these filters, flat-fields should be taken to mask regions with small-scale structures out. To insert the main neutral density filter, use the command:

   TO> mainfiltnd 2

to insert 0.3 neutral density filter (see the table below). The available options are the following:

mainfiltnd	ND	useful window
1	0	-
2	0.3	[500:1600,1400:2800]
3	0.9	[500:1600,1900:3000]
4	1.3	[600:1600,1400:3000]
5	1.8	[500:1600,1400:2800]
6	3.0	[1050:1550,1900:3000]

6.5 Quick-look spectrum extraction

Run the ISIS quick-look script at IRAF with e.g.:

   ecl> ing

   ing> isis

   isis> isis_ql r1234567 252

where the image name is given without the '.fit' extension, and the last number on the line 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.

Back to the top

You can either write your data on a DVD (~4 Gb)

• Get a DVD from your support astronomer or TO, and put the DVD in the DVD burner (located in the computer room)
• Just follow the instructions.

OR on a DAT tape (~12.5 Gb)

• Get a DAT tape from your support astronomer or TO, and put the tape in the DAT drive in whtdrpc2
• Open up an xterm and cd /obsdata/wht?/YYYYMMDD
  
• Use the tar command to write the data tape; e.g. : tar -cvf /dev/rmt/0lbn .