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Setting Up the Telescope in the Afternoon

You should plan to start setting up for your nights observing in the afternoon before observing at a bare minimum. This will allow you to contact the technical staff to help you before they leave for the day.

  • check that the instrument is working properly, taking Bias frames, dome flats, and dark frames.
  • You may also want to check the focus of the imager. This can be done by bringing an internal mask into the beam, and turning on a back illumination light. The holes in this mask can be focused by moving the imager focus control on the Imager control PC up and down until the points of light are as small as possible.
  • Finally check to make sure the telescope is working properly
    1. Make sure the Console on and Power on buttons (located above the CD player) are illuminated. If not - turn them on.
    2. Hit the BREAK key on the telescope computer to get the login prompt.

    3. Log in as TELESCOPE. The password is written in the back of the CCD temperature book.
    4. Give the observer ID. You can create your own or just use someone elses. If you are using the IMAGER I can recommend BRIAN or JEN, if using CASPIR, try PETER or WOOD. It doesn't really matter who you log in as ... you can always reconfigure parameters on the command line.
    5. At the TEL> prompt, type STARTUP. The telscope will start up by itself and return the TEL> prompt when finished. If the WARNING or ERROR lights (located above the telescope display screen) come on.
    6. Type display config to view the configuration of the telescope.
      • Make sure you are set up for the correct focal station:
        • DBS - Nasmyth A
        • IMAGER - Nasmyth B
        • CASPIR - Cassegrain
        If the focal station is wrong, you can change this by typing:
        configure focal_station nasmyth_b
        at the TEL> prompt.
      • Unless you are doing something unusual, you will need to use the rotators. Make sure you have plenty of twisting space. Good values to set the rotator limits to are -520 - +520. If the limits are set to less than this type:
        configure rotator_ccw_limit -520
        configure rotator_cw_limit +520
        You also need the rotator to rotate with the field of view:
        configure rotator_reference position_angle

      NOTE: Complete information about configuring the telescope is contained in the COMMANDS REFERENCE MANUAL and the OBSERVERS MANUAL which are located in the console room. You should refer to these texts if you want to know how to configure something.

    7. Type display to return to the telescope display screen.

      Filling the Dewars

      THE DEWAR NEEDS TO BE FILLED EVERY TWELVE HOURS. DO IT AT THE START AND END OF THE NIGHT. IT IS THE OBSERVER'S RESPONSIBILITY TO MAKE SURE THAT THE DEWARS ARE FILLED.

      You should also ask the technical staff in the afternoon whether you need to keep additional dewars cold for the next observer.

      FOR SAFETY REASONS, WHEN FILLING THE DEWAR, PLEASE WEAR SAFETY GOGGLES AND USE THE GLOVES PROVIDED. AVOID STANDING UNDERNEATH OR VERY CLOSE TO THE DEWAR SINCE LIQUID NITROGEN WILL SPILL OUT WHEN THE DEWAR IS FULL.

      Opening up

      To Make the telescope point properly, it is necessary to zero point the pointing, and to define an aperture which the telescope knows is the center of the field you are interested in.

      Calibrating the Pointing

      The first things you have to look for are the pre-determined offsets for each instrument. These are written on the white-board under telescope offsets. Before fiddling the pointing you should enter these. Type:
      calibrate pointing a b
      e.g. calibrate pointing -46 -514

      Next, go to a bright star with position supplied in the Astronomical Almanac which is usually near the computer console, and make sure that you either see it in the TV guider, or

      Take an image with whatever imaging device you have (TV/GUIDE CCD/TIPTILT/CCD) and see that it is where it is supposed to be. If it isn't, move the telescope so that star lands where it should, and then either press the calibrate pointing button on the console, or type calibrate point at the telescope prompt.
      If the star is no where to be seen, try a bright globular cluster - it is much easier to centre up on.

      Calibrating an Aperture

      At the telescope prompt type calibrate aperture aa
      where aa can be any name.
      Follow the ensuing instructions. Centre the star on the screen/CCD using the telescope controls (mark with a marker on the screen to remind you where this is). Once you have told the program that this has been accomplished, it will rotate the telescope a 120 degrees. While it does this, if you have a detector (e.g. autoguider or tiptilt) that has a small field of view, it will usually rotate the star out of your field of view. It is best therefore to try to keep the star within the box using the telescope control. When it has finished rotating, recentre the star on the marked point, and then continue.
      Answer N to question about defining a slit. You do not want to calibrate orientation, and don't worry if the star moves out of position once calibrating is done.
      At the end of this procedure, aperture aa is defined and is automatically selected as the current aperture. That means that the telescope is moved to align this position with the optical axis.

      CICADA - The Computer Interface

      1. Log on to the Sun station named mouldy as yourself. You should already have an account on the system. If not, you will have to submit an account request.
      2. In an xterm, type cicada &. Cicada is the software which controls the CCD instrumentation.

      3. Under the menu Start observing, select Imager. This will bring up the AM3200 Controller Window

      4. If a warning box appears concerning user-defined FITS keywords from a previous cicada session, choose to display the FITS keywords window. If this window does not appear, under the Options menu, select Show Fits Keyword Window.

        Here you enter non-default keywords that you want in the headers of the FITS images. Most of the standard iraf keywords are automatically put in, but you MUST enter the keyword FILTER and the value in this box. The filter keyword is not automatically put in the headers at the moment since Cicada does not directly control the filter wheel.

      5. You will need to start up an Ximtool for Cicada to display things in. This Ximtool is owned by Cicada - you must start up another private Ximtool elsewhere if you want to reduce your data. To get Cicada's Ximtool, under the Tools menu select Start Ximtool.
      6. The default parameters in the Cicada (AM3200) window need to be set to something reasonable...
        • Filename prefix I usually leave this as ccd - the images are then called ccd0001, ccd0002 etc... You can change this to whatever you want.
        • Run Number This is the number of your first image and will increment by 1 as each image is taken.
        • X bin, Y bin The 2.3m has a scale of ~ 0.3" per pixel. Hence for most work 1x1 binning is fine.
        • Overscan columns I recommend at least 100.

          Since the field of view of the Imager is much smaller than the CCD, you will need to set the values below in order to window the detector to the size of the field.
        • X-offset-1, Y-offset-1
        • Width-1 , Height-1

        If this is the first night of your run you will need to clear the data disk and have a directory owned by you created. To do this, under the Tools menu select Start Teldisk. Then select Clear Disk. This will create a directory called /data/mallorn/cicada/ yourusername. If this does not happen, please contact sysman@mso.
      7. To tell Cicada where to put your images (the default is your home area - and you won't fit many images in there), under the Options menu, select Preferences. Then type in the path of the directory you want the data to go into. e.g. /data/mallorn/cicada/ yourusername.
      8. Initialise the CCD hardware at the start of each night and every time the bias level is considerably higher or lower than it should be (this should happen rarely with the new controller). Under the menu Actions, choose Initialise CCD Hardware. Two windows will pop up as it initialises, a Temperature etc window and a Voltages window. Once the voltages window appears - initialisation is complete and you can dismiss these 2 windows. Check the bias level to make sure everything is fine.
      9. If you wish to change the gain for your images, under the AM3200 menu, select Edit Gain Values. It is advisable that you talk to the Technical Staff before doing this, as they know what the current status of the detector is. You will need to re-initialise the hardware once you have changed the gain value.

        Data Calibration

        Like any CCD system, certain data calibrations are recommended for proper data reduction, and some data calibration data is good to make sure there is nothing wrong with your data. We recommend taking
      10. A Dark Frame (600s). There should be essentially no dark signal if things are properly working.
      11. A series of 10 Biases. The bias level should be around 1000-1200 counts if the hardware has been initialised properly.
      12. A series of twilight flats (although lots of exposures in V, R, and I will allow you to create a data flat by medianing of your data set).

        13. Taking data

        Taking Data at the 2.3m is as easy as making sure the imager is correctly configured, and then using cicada to take an object exposure. Configuring the imager is done on the left last computer on the main desk - the monitor is labelled IMAGER/DBS.
        1. This is usually left open either for the DBS or the IMAGER. If it is DBS mode, select from the top left corner, the DBS menu and EXIT. This will leave you with a DOS prompt.
        2. Type imager. You will have a grey screen with 2 menus. Go to Imager and then select Control/Status (or F6). This should bring up a screen with lots of columns topped with M1, M2 etc.. A few important bits...
        3. Slide: This moves the autoguider camera around its focal plane. -52 is a good place to keep it so that it can see a pick off mirror outside the CCD FOV. 0 places the small camera in the centre of the imaging field where it almost completely vignettes the CCD.
        4. Turret: Clear for imaging, but other modes available for focusing up the instrument, or testing instrument during the daytime, when used in conjunction with the Back Illumination: in
        5. T100 Filter: one place filters can be placed
          6. Tilttune: for tuning the ramp filter?
        6. T50 filter: another place filter can be placed. (usually clear) CBeamFocus: 0 by default, but should be tuned during the day using the mask on the turret with the back illumination, if you are using filters in the T50 area.
        7. PBeamFilter: U,B,V,R,I Here is where you change your filter if you are using the standard UBVRI.
        8. Camfocus: 0, but should be tuned to make sure telescope is in focus using the mask on the turret with the back illumination turned on.

          9. Focussing the Telescope

          First, you should, during the day, ensure that the instrument is in focus. This is accomplished by putting a mask in with the turret on the Imager control PC, and turning the back illumination on. You can then take a very short image of this mask with the CCD, and adjust the Camfocus (or CBeam focus if you are using filters in this part of the imager) so that the mask appears as a series of sharp dots on the CCD.
          There are two main ways of focussing the telescope. A quick and dirty way which seems to work quite well if you are using the DBS/Imager, and a more involved (and more typical) process if this isn't working for you.

          Quick & Dirty

            The idea here is to use the auto-guiding camera of the Imager (or you may find it easier to move the telescope over the Nasmyth A, and use the DBS autoguider), and image a star in realtime, adjusting the focus until the star is in focus. You should, if the seeing is 2" or better, be able to adjust the focus to about 4 units with this method.

            The more standard approach

            Take a series of images, offseting the telescope between each image, and then read out the image. You can then use IRAF, or GIT to see which image is the best, and move the telescope to that focus value. Make sure that cicada is set to not readout/flush images between exposures, but flush the image manually at the beginning of the first exposure! The board may give you some guidance where to put the focus. I increment by about 4 units of focus, and make sure you do a different offset on the last exposure, so you know which is your first image.

            Saving Data to Tape

            1. There is 1 DAT drive and 1 EXABYTE drive located on mudslide. You should have brought your own DAT or EXABYTE tapes with you on which to save your data.
            2. In an xterm on mudslide type:
              • allocate mt0 - for the uncompressed DAT drive
              • allocate mt1 - for the compressed DAT drive
              • allocate ex0 - for the uncompressed EXABYTE drive
              • allocate ex1 - for the compressed EXABYTE drive
            3. Put your new tape in the relevant drive
            4. CICADA saves the imager files as fits files so you can either write these with IRAF or tar them onto the tape. I always tar them onto the tape. The command will be something like:
              tar cvf $TAPE dec11/* if we use the example of the data put into a directory called dec11.

              Shutting Down the Telescope

              The telescope is made to shutdown very quickly an efficiently

            5. Simply typing shutdown at the TEL> prompt will completely shutdown the telescope for you. Watch the computer screen to make sure everything shuts down OK.

              If you get a message that says Telescope not safe to leave unattended then try starting up the telescope points 3,4 and 5 again and then shutting down once more. If this message still comes back, go out into the dome and make sure that the primary mirror cover is closed and that the dome shutters are closed. Then write a telescope fault report and leave it up to the technicians.

              If the dome is not closed, it is best to call for help.

          1. Make sure you have filled the dewar/s!. If you shutdown and you need to rotate the instrument to fill a dewar, you must restart the Telescope control.
            At the end of your run, please leave a observing report so that we can know how things are going, what can be improved, etc.