Back to the drawing board?

So, I took out the shorter FL rig with the 66mm f/6 scope and the 135mm lens in the hopes that I could have an easier time, a more positive experience.   Nope.

I didn't charge the battery from the previous session to see if I could go two nights
of powering the mount on a full charge.  I think the answer is a qualified "yes".

I had decided to shoot some part of the flux nebula (IFN) near M81/82.   I figured that the proximity to Polaris and the short FL of the system would make it easy to shoot 15 min subexposures.

My plan was to shoot 21 subs at 15 min equaling a little over 5 hours.

After setting everything up, I did a test exposure and there was that awful, familiar vertical trailing.  I changed the calibration step duration from 1000 to 400 in PHD2.   I turned the autoguiding camera about 30 degrees to the left and I re-calibrated the autoguiding.   I watched the PHD2 window and it seemed fine.   It was guiding perfectly and there was no obvious error -- expect that every so often, the guider would send a 500+ms command to move the mount.  I didn't think much of this at the time.

It didn't help that 2-10 mph winds were pushing the laptop tent around.

The next test 15 min exposure showed less trailing.  I decided that the errors were perhaps caused by the wind and that things would calm down eventually.  So, I set up Backyard EOS to shoot 21 subexposures at 15 min each.  800 ASA, F/3.2.   I also changed the calibration step to 660.  

Why change the calibration step again?   Who knows.

Went in, took a nap for about an hour and a half, came out and saw trailing in all of the 14 shots that had been taken.   >sigh<   I did examine the shots and it looked promising as some tweaking with the rudimentary "curves" function in BackyardEOS revealed patches of faint red near M81/M82 and throughout the frame.   But still, every frame showed trailing.

If you looked at the successive frames, it was obvious something was wrong as M81/82 starts out in the upper right and then 2 hours later, they are about 1/3 of the way down on the frame.   In retrospect, it almost seems like there was no (or possibly very poor) guiding in declination. 

I tried other settings in PHD2 and shot another 15 min exposure and I got the same trailing.   It just didn't make sense as I wasn't getting any error messages from PHD2. 

I decided I needed to pack up.  But before I called it quits, I slewed the scope to the Rho Ophiuchi area near Scorpius.   I changed the calibration step to 250 (again why?) and got the autoguiding to work fine.  And I shot two perfectly fine 5 min shots.    I should have tried a 15 min shot, but I was tired and decided to call it a night.

Basically, I had a problem/technical issue and I didn't know how to fix it.   Perhaps, I should have used the 50mm finder/guidescope instead?   I had been out the previous night and I managed to shoot a several dozen 5 min shots of the Leo Trio.   But even on the previous night, there were problems maybe every 8th frame?   Perhaps periodic error is to blame and I should run the Eqmod software to deal with it?     An interesting note is that the Sirius/Heq5 Pro mount has about a 638 sec worm period.   Does that mean that exposures longer than that will always have problems?    If so, then periodic error correction should addresss the issue. 

Hm...


[Later:  I forgot to mention one crucial detail from this session:   I didn't polar align.  In retrospect, that was probably the biggest mistake and it offers a plausible explanation for my problems.  I assumed that since the mount was weighed down by the 50 lb battery that polar alignment would be good enough.    But every time I setup for an imaging run -- even though I keep the mount in the same place -- I move the battery around a bit.  And the act of removing/adding the OTA/telescope surely adds/releases some stresses in the aluminum structure.   I wouldn't be surprised if the mount was off by 2mm in some random direction.   The fact that M81/82 seemed to drift over 2-3 hours of subexposures speaks to polar alignment issues.  Still I'm faced with the fact that PHD2 didn't fix the drift...which in theory it's supposed to do.  I should have shot a 15min exposure of the Rho Ophiuchi area.   The bottom line here is that by not polar aligning at the beginning, I added another layer of unknowns to the guiding problems.   Lesson:  Don't take shortcuts.]