Saturday, April 20, 2013

The Things We Forget

I pulled Big Bertha out this evening to do some observing, since we had a pretty clear sky.  To my disappointment, putting four more casters under it did not solve the problem of smooth motion across the chip seal.  Perhaps the wider wheels are going to be necessary -- or just store it in the main garage, where it can roll on concrete.

I also decided to use the digital setting circles -- and to show you how long it has been since I used it, the Celestron Advanced AstroMaster would not turn on.  The 9V battery that powers it was completely dead.  When I opened the case, I found that the battery was leaking, but fortunately, the battery compartment is well isolated from the rest of the components.

Then I powered it up and tried to use it.  The way the Celestron AAM works (and I suspect many of the similar products) is that when you power it up, it asks you to set the declination of the scope to 0 degrees, hit enter, then select two or more bright stars, point the telescope to each of them, then hit enter.  And it produces nonsensical results tonight.  Huh?  This used to work.

So I started Google-ing for instructions.  I may have found the answer -- a really thorough review of the Celestron CI-700 and the Celestron AAM written, in 2007.  The important quote that may explain why this wasn't working:
The operating instructions that came with the Advanced AstroMaster also leave a bit to be desired. At the beginning of the manual (what might be considered the quick start section), it tells you to hit the ENTER button when you see the “SET DEC=0” prompt. Later, in a more detailed section, it tells you that you need to move the declination axis to the zero degree setting. It also appears that you need to start out with the declination axis at 90 degrees, then move it to 0.
Of course, the mount was never at 90 degrees when I started the AAM.  It was usually pretty close to 0.  This may explain the problem, especially because I suspect that the AAM uses rotation through 90 degrees to calibrate the encoders.

And here, in a copy of the Celestron AAM manual, on page 7, is a warning that for a German equatorial mount (like the CI-700):
[T]he first alignment star must be east of the meridian.
 And of course, every alignment star I used was west of the meridian. 


  1. Hi, I have aquired a Celestron Celestar C8 Deluxe that has an Advanced Astro Master, I have not been able to get it to work, I have seen nothing in the manuals about having the scope DEC at 90 when powering on, did doing that correct your AAM?

  2. Thanks, I just tried that and it still didn't work.