Preparation for observing by the Telescope Operator

The following checklist is for normal operation in good weather conditions. However, some of the following actions should be done also in bad weather. Remember that the dome may not be opened in adverse weather conditions, i.e. with strong winds over 80km/h, with more than 90 percent humidity, with ice on the dome (which can fall in), and with high outside dust levels. Note that, if at night the humidity drops quickly from 100 percent (after rain or dense fog), the dome will be opened only at below 80 percent, in order to give the dome structure time to dry up.

1. When convenient, e.g. in the afternoon, input any long catalogue files that the observer may require, such as seeing standards or target lists for the observer, by typing at the user interface console:

   INPUT filename

   where filename is the name of the catalogue (Section ). If a file extension is not specified, it is assumed to be `.CAT'. A maximum of 500 objects can be entered.

2. During or after dinner discuss with the observer(s) any special requirements they may have, and determined at what time they want to open up. Good communication between the TO and SA and the observer(s) is essential for a smooth operation of the telescope.
3. With the telescope at Zenith (Cassegrain) or Access Park (Prime) position, fill the CCD dewar(s) with liquid Nitrogen. This is normally the first thing the Telescope Operator does after dinner. Note that the dewars have to be topped up whatever the outside weather conditions.
4. Check that the INPUT fan on the ground floor and the EXTRACTOR fan on the second floor near the telescope base are both on. The latter fan can be reached via the small Coude room, opposite the CLIP Centre (beware oil on the floor!). If the fan is not working, switch it on by pressing the green start button. This will also start the INPUT fan on the ground floor. Both fans are essential in the control of the dome temperature and hence the dome seeing.

   Obviously, when the dome may not be opened because of adverse weather conditions, these fans must be or remain switched off.

5. Close all doors and pull down the blinds in the library and the restroom.
6. Switch off all unnecessary white lights. Safety lights will automatically come on at various points in the building.
7. In the afternoon, as soon as the outside temperature becomes lower than the inside temperature, open the dome as follows, in order to thoroughly ventilate the dome interior: Turn the dome slit position to the East (azimuth = 90 degrees) and raise the Upper Shutter to an aperture of about 1 metre. Press the RAISEMICRO on the Engineering Rack until the MAIN OVER TRAVEL indicator light switches off, and then press the RAISEMAIN button until the required aperture is made.
8. Remove lids from the fan ducts (if necessary) and start the dome fans, subject to current practice. Replace fan covers if it clouds up.
9. Open the dome fully by pressing again the RAISEMAIN for about 10 seconds; the MAIN OVER TRAVEL light should now be on again. Further, the dome lights should be extinguished to avoid throwing unwanted light in the direction of the other telescopes when the dome is rotated.
10. Execute the encoder ZEROSET procedure, in order to obtain the hardware zeropoints of the Ferranti Encoders. This procedure consists of carefully moving the telescope in engineering mode through zenith in both RA and Dec, and is described in detail in section .
11. Open the cover of the Finder by pulling the cord, and attach the ring to a rivet located on the mirror cell nearby.
12. If working at Cassegrain remove the Primary Mirror Plug as follows:  
    1. Change over to engineering mode by pressing the ENGCOMP button on the Telescope Control Desk.
    2. Move the telescope to the North Horizon Limit; use an Hour Angle of exactly 24.00 hours, so that the telescope needs to be moved in Declination only.
    3. Press the Declination QM (Quick Motion) button on the Engeneering Rack until the green light comes on to signal that the mode is engaged. The corresponding light of the SM (Slow Motion) button must be off. If wanted, one can adjust the quick motion speed by turning the QM RATE dial just above these buttons.
    4. Press the Declination + button, which actually moves the telescope, until the alarm sounds as sign that the telescope has run into a limit. Now press the Accept button on the Control Desk to switch the alarm off.
    5. Turn the key-operated LIMIT switch on the Engineering Rack to the O/R position (limit override). The key no.6 must be inserted before the switch can be operated. (If the Key is not in the switch, it will be in the Key Press, which in its turn can only be opened by the Duty Officer!)
    6. Repeat steps d) and e). This time there will be no alarm, but the telescope will halt in horizontal position when it runs into a second limit switch.
    7. Use the ladder on the observing floor to get at the primary-mirror plug. Place the ladder such that it fits within the two brackets on the bottom half of the cube. Climb into the cube and remove the plug. Put the ladder in a safe place on the dome floor.
    8. Press the Declination - button to move the Telescope back to the the pole position at declination 90.
    9. Turn the LIMIT switch to the NULL position and push the Declination SM button.
    10. Change over to computer mode by turning the spring-loaded key on the Control Desk against the spring for a moment. Subsequently, press the ZP on the System Control panel on the Control Desk in order to park the telescope at zenith.

        Beware! If no ZEROSET was done previously, or if there are problems with the encoders, the telescope can move to an incorrect position when sent to zenith in computer mode. Therefore, keep an eye on the RA and Dec gauges or check the telescopes behaviour through the control room window. Alternatively, move to zenith in engineering mode.

13. If not yet done before, change over to Computer Mode by turning the key on the Control Desk to the right against the spring. The COMP light should come on and the key will spring back to its original position. If the COMP light does not come on check that:
    1. both RA and Dec slow motion (SM) clamps are engaged (indicator lamps on Engineering Rack, bay 5).
    2. the RESET button has been pressed after an emergency stop.
    3. No alarms are active.
14. If it is dark enough, switch on the TV cameras and their corresponding monitors (Finder and, if appropriate, Cassegrain) and the Autoguider, using the buttons on the control desk (see figure ).
15. Open the secondary-mirror cover and primary-mirror cover IN THAT ORDER (something might drop from the Top End!), by operating the PRIMARY MIRROR COVER and SECONDARY MIRROR COVER OPEN buttons on the Engineering Rack. The secondary-mirror cover button needs to be pressed only once but the primary mirror cover button must be kept depressed until the OPEN light is illuminated. Further, note that the secondary-mirror cover must also be opened when operating at Prime Focus.
16. If SET, GUIDE or INCREMENT rates other than the defaults are to be used, enter these via the User Interface (see Section ) and press the corresponding buttons on the Telescope Control Desk to `activate' the new values.
17. Focus the telescope (section ). In Cassegrain mode, this is done by visual inspection of the image of a bright star on the Cassegrain TV (which is accurate enough). The focussing procedure for Prime Focus work uses a sequence of 7 short exposures on the CCD (under ADAM control) of a star for different focal positions to determine the best focus setting. The FOCUS procedure is described in detail in section .
18. Perform a Single star SNAFU on a star near the zenith in order to determine a software zeropoint for the Pointing Model (see Section ). The Telescope Operator will normally take a star from the SAO Catalogue within 2 degrees from zenith with an eye on the ensueing determination of the finder zeropoint (very important for Prime Focus work).

    The SNAFU at the Cassegrain Focus is done as follows:

    1. Enter the coordinates of the star at the User Interface (see section ): use the SOURCE command and use object name e.g. SS.
    2. Drive the telescope to the object: make the SNAFU star the next object with the command NEXT SS and press the SRCE button on the Telescope Control Desk.
    3. Wait until the telescope is tracking accurately.
    4. Type at User Interface:-

       SNAFU

    5. Turn up the gain of the Cassegrain TV until the star is clearly visible and use the handset to place the star at the required reference point (usually the Grinnell crosswires).
    6. When satisfied with the SNAFU star's position, press the ack button on the Control Desk (Bay 2, Rack 3) to reset the collimation corrections in the pointing model.
    The SNAFU at Prime Focus is done completely differently by means of a test GLANCE exposure on the prime focus CCD, under ADAM control (see section for more details):
    1. Startup ADAM (See the Prime Focus User Guide)
    2. Move the rotator to position angle 180 with the ADAM command ROTPOS 180.
    3. Slew the telescope to the SNAFU star, as for Cassegrain mode.
    4. Take a test GLANCE exposure of the field (1-5 seconds; use filters if the star is very bright). The CCD image will appear on the LEXIDATA and the star should be obviously visible near the centre of the chip.
    5. Use the MOVESTAR command, and locate the star with the cursor. ADAM wil now calculate a position correction and send those via the link to the Telescope Control Computer. The telescope will move to the corrected position: the star will move on the Finder TV image.
    6. Mark the position of the star now on the Finder TV screen with a felt pen or similar marker.
    7. Now send the telescope again to the original position by pushing the SCRE button.
    8. Type at the User Interface:

       SNAFU

       and move the telescope with the handset such that the star image on the finder will coincide with the position marker.

    9. Press the ACK
    The reason behind the last three steps is that allthough ADAM sends the corrections to the Telescope Control Program, this does not update the pointing model zeropoint. That is done in the same way as for Cassegrain mode during the last three steps.
19. Finally, determine the Finder Zero Point with the telescope still pointing to the SNAFU star:
    1. Select the Finder on the TV monitor on the Control Desk.
    2. The SNAFU star must now be visible at, or very close to, the centre of the finder field. It's position corresponds to the centre of the Cassegrain field.
    3. Press the MENU button and select "SET FINDER ZERO POINT".
    4. Put the cross upon the star with the Grinnell joystick (on the Control Desk).
    5. Press the Enter button; this sometimes has to be repeated.