Saturday, October 5, 2013

CalStar - 2nd night

I spent the day trying to figure out what is wrong with my scope:

  • I checked the flatness of the image - minimum tilt
  • Cleaned the OAG prism
  • Cleaned the corrector plate (very careful - there was a lot of sand and dust on it)
  • Took exact latitude and longitude from the GPS system
  • Checked all mechanical connections on the mount
Then at the beginning of the night, I continued to focus on improving the guiding (if I can't figure it out, I could go home).

I used AlignMaster for polar alignment again. I did 3 iterations and in the last iteration, the correction was minimal. Verified collumation - good (below 1").

Mark Scrivener and John Wainwright gave me a couple of good tips:
  1. Use the ASCOM driver for guiding - not through the RJ45 cable
  2. Disable guiding commands in PHD and just see where the guidestar moves
  3. Guide (or test) with the main camera - not the Lodestar. This rules out any issues with the OAG or such.
I calibrated PHD near the equator and ran it without guiding. It showed an almost perfect polar alignment - even after 10 minutes, the trendline looked completely horizontal. And the RA trendline went up very straight and smooth. So, the scope is fine, polar alignment is great. Repeated the same with the lodestar - same result. So, the OAG is fine too.

When I was almost ready to declare defeat, one of my neighbours came over to me and asked what was wrong. I walked him through everything. He then wanted to look at my PHD parameters. And he pointed out that my "Max Duration" was too low (I had it at 200). He recommended to set it to 800...
... and voila! Suddenly guiding errors dropped below 0.2 arsec!!! AAAAAHHHHHHH!

I then started guiding again. Watched it for a little - looked really good.

I woke up at 1am to check if SGPro started imaging the 2nd target - worked!!!

And then in the morning, I found out that at 2am guiding completely stopped!!!!!! NOOOOOOOOOO!!!

But the images from the first target were now MUCH better:
This is much better. Although for a 1x1 binned luminance subframe it's still a little blurry.