Ad Astra Observatory

A,

Meridian flips don’t work on my mount. The RA motor lags by several

degrees in clockwise (RA+) on every slew.

I tested to see if the error got larger when jumping back and forth
without recentering in between, but strangely it didn’t — the star was
always in more or less the same place, off by 2 or 3 degrees in RA- from
where it should be. About half the finder width.

So I played with the weights/balance, and frustrated myself badly. I

figured out some things that are worrisome:

1) The reticle is about 1# lighter than the camera, so the scope is all
off-balance while the reticle is in place.

2) The (*&%(&*$*) reticle was not centered in the (*$(*#$*^$) FOV, so
when I centered a star, swapped in the camera, and refocused, the star
was way off to one side in the camera FOV. I fixed this (by adjusting
the reticle).

3) I worried that the offcenter reticle was screwing up my polar
alignment/pointing model, but after rebuilding the model with a centered
reticle, I found that this was not a problem (which is the only success
I had during the night).

4) I played with the balance (but later realized that it was all
worthless because I was doing it with the reticle in, so adjusting to
that was stupid…) and I *think* that I got the meridian flip working a

little better, but I’m not sure. One way or another, it was nowhere near
centered, but maybe at some point I could get it to be within the
eyepiece instead of within the finder? Can’t quite recall.

5) I have what I fear is a serious balance problem, because when I slew
in RA, in one direction (I think RA+), the star will stop when I release
the button. But in the other direction, the star keeps moving for
several seconds after I release the button. It’s like it’s doing

backlash compensation or something? I’m more worried that this is a
balance problem. Have you seen this kind of overrun?

6) I have the clutches tightened down as hard as I can get them, but I
can still grab the RA axis and shift it by several arcmin — I’m pretty
sure this is the backlash in the axis, and probably not something I can
do anything about..?

7) Even though my pointing model says A: -2 E: -1, I’m getting a
significant amount of drift over 30min. The drift is both in RA (which I
can attribute to periodic error, and is thus guideable) and DEC (which I
attribute to polar misalignment, but could be something else). It’s
obviously less than it was, but it’s probably 10′ over 30min.

8) At one point, I freaked myself out worrying about cable tension, so I

removed all the wires from where they were strapped to the mount. I need
to redo my wiring harness.

In all, last night was one of those “two steps back” kind of affairs. As
it sits, the camera is in place in focused, and the mount is in theory
polar aligned. But there’s no pointing model, the mount is clearly
off-balance, and I am *not* ready to image tonight, even unguided.

sigh. need help.

I was going to call you last night, but I decided to give you a night
off of tech support. 🙂

J