Ad Astra Observatory

When I am building a Pointing Model in the Gemini (where you select and center bright stars and then the Gemini figures out hot to GOTO properly), the “residual error” which is displayed after each alignment seems to start large (~30′) and then get smaller until it reaches some plateau (I can often get it to drop to 0′ or 1′).

I have not been able to figure out whether this “goes to 0” means that:

1) I have a sensibly perfect polar alignment, or
2) I have a horrible polar alignment, but now Gemini knows how to compensate for it.

I worry about my polar alignment, so I have been trying the polar alignment tools that Gemini provides.

There are 2 polar alignment tools in the Gemini menu.
Polar Align Assist requires *no pointing model*.
Polar Axis Correct requires *pointing model to be set up with at least 5 stars*.

I was going to do Polar Axis Correction, so I set up my pointing model. When I set up the pointing model, this is what happens:

1) cold start
2) goto bright star -> synchronize
3) goto another bright star -> additional align (this is the important part) A: is usually like 34′ and E: is similar, maybe 20′
4) goto a third star -> additional align now A: is something like 14′ and E is 1′ or so

5) goto a 4th, 5th, etc. star, meridian flipping as necessary At some point, I get A: 0′ and E: 1′ and then I stop building the pointing model.

So the question is, am I building in a correction for a misaligned polar axis into the pointing model? I’m unsure why the errors seem to get smaller and smaller as I put in more stars.

What I’m saying is that I think that I’m misreading those numbers. They are not telling me that my *polar alignment* is great, just that the *pointing model* is good enough to overcome my crappy polar alignment.

I need to get this part figured out. I think my polar alignment is off.

I need to do my “CCD alignment” routine again. One problem that I’m having is that I have no earthly idea how to get the Gemini to go at 2x sidereal. I’ve sent James Bielaga an email asking him how to get that
done. Without getting the drive to turn off in one direction, the alignment routine will not be as accurate.

I did the polar axis correction routine over the weekend. It suggested I move the polar axis some in azimuth, which I expected. BTW, my polar alignment scope still says that Polaris is in the wrong spot. I’m not sure what to make of that. I didn’t try any long exposures. I’m so tired right now that I kept bumping into the mount and screwing up my pointing model.