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3.7 Indexing

It is very possible that you will not have to Index the telescope before you find your first object. The telescope has a good memory of where it was when it was last parked so you should be able to target your first field and go directly there. You might want to center it up a little bit and then Reset the Encoders (E button in ACE).

However, if your field does not show up in the CCD image on your first attempt, try this: First, do a Zenith Park (Z button) and then Home the telescope (the dark blue house button). This takes a minute or two, but it will find the RA and Dec Home switches at the Zenith and then reset the encoders to that known position. The pointing should be within 30” of your field when you move next time. This works 95% of the time, but if for some reason it doesn’t work you have to do a little more advanced work:

Go up into the dome and identify a bright star through the slit. Center that star in the Telrad bullseye using the Hand Paddle on the East wall upstairs. Then center it in the finder scope cross hairs. Make sure the finder scope end cap is off and the cross hairs are illuminated. Then go down stairs and center it in CCD. It’s a good idea to put a narrow band filter in before you expose the CCD to a bright star. Take a test exposure of about 1/10 second.

The star should be visible somewhere in the CCD field. Center in the field using the set buttons on the soft Hand Paddle in ACE. You can then find the coordinates of that star by right clicking on the ACE interface and bringing up the Bright Stars Telescope Object File (Bright Stars.TOF). Select your star from this list by double clicking on it. Once you have the star entered into the coordinate field and the star is centered in the CCD, you can then Reset the Encoders (E button in ACE) to this position.


next previous contents
Next: 3.8 Centering the X-Y Stage Previous: Biases

Updated: 9/14/99