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Mount Debugging

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Mount Debugging was created by Rick Wayne

Yes, I have engaged in an expedition to scale Mount Debugging almost every time I visit ProgrammerLand. :-)

I am trying to better polar-align my iOptron CEM25P. I have been using the Polar Alignment Assistant (hereinafter PAA) feature in Ekos. Cool tool!

Except that when I go off and guide, I am not getting better results. In fact PHD's Guide Assistant estimates my polar alignment error to be bigger than the initial error shown by the Ekos tool before I corrected, and indeed going back and running the Ekos tool afterwards seems to yield results almost as bad. Too, if I squint again through the polar scope after the process, Polaris is nowhere near where it's supposed to be on the reticle.

I'm at the hypothesis-generating stage, would love to hear some others.
  1. You totally kicked the tripod. (Really, I didn't.)
  2. The tripod settled into the ground over time. (It was on a concrete driveway.)
  3. The Fortune Cookie Reveal -- like a fortune cookie that reports "What you just ate wasn't really chicken", maybe that wasn't Polaris in the polar scope? (It was. Honest.)
  4. I didn't get the star close enough to the indicated dot (but if I do two PAA runs in succession, the second says I'm at least as good as the first)
  5. I should have slewed the scope in DEC away from the Pole, to sweep out a larger sky area for the PAA's capture/solves
  6. It took me too long to adjust onto the dot, so that the star had rotated away from its original position
#6 is at least plausible, given that it takes over 20 seconds between the start of a DSLR exposure and refreshing the screen, the adjustment takes at least 5 minutes. I could use the guidescope instead of the main scope, and buy much much faster refreshes at the cost of some precision (162mm F/L vs. 332mm, but a smaller sensor on the guidescope). The fact that the guidescope is never perfectly coaxial with the main scope should not matter -- right? It's the difference between the images that allows the PAA to calculate the actual alignment.

Any other ideas? TIA!
Last edit: 5 years 10 months ago by Rick Wayne.
5 years 10 months ago #25723

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Replied by Andrew on topic Mount Debugging

Use your guide scope, The refresh rates alone are worth it. Being a little out of collimation is fine, the procedure is only interested in the center of rotation, not what is effectively cone error.
5 years 10 months ago #25777

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