University of Michigan - Department of Astronomy

Version: scope

Coordinate Systems and Telescopes

You must complete the planetarium or celestial sphere part before doing this section

Preliminary question:

How would you tell what system a telescope is set up to use? (hint: both systems have an up-down coordinate (horizontal axis) and a rotating coordinate. Figure out what direction the axis points for the rotating coordinate.)

Part 1: The 0.4 m

Your GSI will take you upstairs to the observatory dome. Look at the how the telescope is set up and answer the following questions.

  1. What system (equatorial or alt-az) is this telescope set up to use? How can you tell?

  2. Which axis (RA, dec, alt or az) does the telescope have to rotate around to track an object?

  3. What direction does that axis point (i.e. if you put your head by the bottom of the telescope mount and look in the direction that axis is pointing, what is the azimuth?)

  4. What is the angle of that axis? Why?

  5. Which direction does it rotate: clockwise or counter-clockwise? Is this the same direction as the Earth? Explain.

Part 2: the C8

For this part, your GSI has set a telescope on a table in the classroom. The tripod will also be available to look at. This telescope can be used as either an alt-az or an equatorially mounted (RA-dec) telescope.

  1. Which system does this telescope use as it is here (sitting on the table)?

  2. Which axis would it have to move to track an object? Explain.

  3. The "wedge" on top of the tripod is used to make this telescope use the other coordinate system. What are the numbers on the wedge for?

  4. What angle would you have to set the wedge to for viewing here in Ann Arbor?

  5. What angle would you have to set the wedge to for viewing on: (a) the equator (b) the arctic circle and (c) the south pole? Explain.

  6. The only motors in this telescope are in the base, which moves the RA or az axis. If you wanted the telescope to track on its own, which system would you use? Why?

  7. If you want it to track, you must also align the axis properly. Label the sketch with the direction the axis has to point (cardinal point, not a number)

tripod with wedge

Last modified:5/11/05