Reading these instructions does not mean that you are qualified to operate this instrument! For training, email Elizabeth or call x56555.

New instructions for the operation of the 20" will appear here once the installation and alignment are complete.

Old Instructions

Starting Up
Operating the 20"
Common Problems
Shutting Down


Starting up

If you plan to use the ccd to display or take images, the computer needs to be wheeled out of darkroom 1104. The set up and use of the computer and ccd is on a different page.

  • Loosen nuts on the two stops at the base of the yoke and slide them down (1 & 5). Re-tighten the nuts so they don't fall out.
  • Turn on the telescope power. The main switch is on the base of the telescope on the east side (2). If something doesn't work right, there is also a switch on top of the yoke that may need to be turned on (3).
  • Turn on the ccd camera coolant cooler. It's the power strip by the tan box on the side nearest the computer (4).
  • Turn on the computer (6). The camera coolant cooler MUST be on before you turn on the computer!
  • Turn on the sidereal drive. The switch is located on the telescope control rack in the northwest corner of the bay (7).
  • Set the right ascension circle:
    • Point to a bright star that you know the name of
    • Look up its coordinates in the Observer's Handbook.
    • To set the RA circle, you need to loosen the screw holding the glass cover on and remove the cover.
    • The setting circles are Vernier scales. Notice the RA circle has a tiny piece of another circle just above it. The RA circle is marked in 5 minute intervals. The piece above it is marked in half-minute intervals. Say we want to set the circles for 8 h 17 m (don't worry about seconds - it's not that accurate). You first line the 0 up to the nearest 5 minutes, in this case 8 h 15 m. The image on the left shows 8 h 15 m. We still have 2 m to go, so look at the 2 on the upper piece and determine which line it is closest to on the RA circle. You then line the 2 up with that line. The image on the right shows 8 h 17 m.
  • Put the RA cover back on over the RA circle.
  • Check the declination circle to see how inaccurate it is. It was last known to be about 0.4 degrees off.

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Operating the 20"

  • There is a lever with a white knob on the end of it near the Declination circle (8). This is the Dec clamp. Be sure to loosen it when you try to move the telescope and then to tighten it when you're done because the telescope will not track properly if it is not tight. Up is locked.
  • There is not an RA clamp.
  • The telescope can be very difficult to move. There is a bar sitting on the polar axis just above the RA circle (9). You can pull it away from the axis and use it as a lever to move the telescope.
  • There is a knob on the paddle that says "Circle Lamps" (10) This controls the lights over the RA and Dec circles.
  • The focus is the top switch on the paddle (11). It's marked as " secondary motion" (because it is actually moving the secondary mirror in and out).

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Common Problems

It is not unusual to have the following occur. Sometimes the problems are easy to fix, sometimes the problems require major work. If you have any problems and cannot fix it easily, please note it in the log book and let Elizabeth Warner know.

  • You see absolutely nothing through the eyepiece (12).
    • Check that you really did remove the lens covers for both the primary and the secondary mirror.
    • The flip mirror inside the CCD may be set so that light is going to the camera and not to the eyepiece. Turn the silver knob by the eyepiece until you hear the clunk as the mirror switches positions (12a).
  • The telescope does not track and you do not hear the drive at all even after you turn it on:
    • Usually this can be solved by playing with the voltage supplies. There is a digital read out with amber numbers (13) near the camera cooler which is hooked up to a voltage supply (13b) sitting on the telescope base. There is a switch on the read out which will switch the display back and forth between + and -. The voltage supply should be adjusted so that the read out shows +15 00 and -15 00, or is at least very close to that. The drive does not work if the + and - voltage supplies are too different.
  • You cannot move in either RA or Dec with the paddle controls.
    • First check to be sure the Dec clamp is tight.
    • Be sure the RA speed switch is switched to fast (14a) or try pushing the Dec slew speed button (14b) while you try to move.
    • If none of this works, it's probably related to a driving problem and needs to be reported.
  • You cannot change the focus (the motor probably went out).
  • You can change the focus, but stars appear like tiny lines instead of point sources (this is caused by excessive vibrations in the drive mechanism).
  • You hear the drive motor on but the telescope does not track (a pin probably got sheared off in the drive mechanism).

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Shutting Down

  • Turn off the sidereal drive.
  • Turn off the computer.
  • Turn off the ccd cooling system.
  • Turn off the main telescope power.
  • Put the telescope in its home position and tighten the stops.
  • Put the lens covers back on the primary and secondary mirrors as well as the finder scopes.

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