Losmandy G11 Gemini II - need help with guiding
Patrick Spencer
I just purchased a new Losmandy G11 mount with Gemini II. The mount is beautiful and built like a tank, but I’m struggling achieve the level of guiding performance I was hoping for.
I’ve tried to be as careful as I can with basic setup procedures. I read the Gemini instructions, and used PHD2 new equipment wizard, so I believe the settings are correct.
Last night was clear with no wind, no wildfire smoke (yay!), and pretty good seeing, so I got a few hours of data that seems relatively unaffected by weather-related variables.
I ran Guiding Assistant and did 2 “baseline’ guiding runs. The reported polar alignment errors were 2.1 arc-min and 1.5 arc-min, so PA doesn’t seem to be an issue.
The best RMS I got was 1.07” and 1.08” Many other segments were 1.3” - 1.4”
The RA error is noticeably higher than the DEC error in many segments.
I have limited experience interpreting PHD2 logs beyond the basics. I would greatly appreciate anyone would would be willing to look at my guiding log and advise if you see any issue I can address and hopefully resolve.
Additional details on my situation in case they’re helpful:
Guide scope resolution = 2.99”/pixel (200mm scope + ZWO ASI290MM)
Imaging location: SW Colorado Springs, elevation 6100, Bortle Class 5
Thank you very much for any help!
Patrick Spencer
TheDesert IsPatient
bw_msgboard
Hi Patrick. I don’t see much here to be alarmed about. Based on the Guiding Assistant results, I think your seeing wasn’t very good although it slowly got better as the night progressed. If we look at the later sequences, the RA rms is higher than Dec but I think you should still have gotten sufficiently round stars in your images. The RA performance is mostly constrained by the residual periodic error, which looks to be around 10 arc-sec peak-peak. You can see that here:
You can see the primary contributor aligns with the worm period of the mount but there are also contributions at lower frequencies. I don’t know if those are harmonic frequencies for this mount, but your best bet would be to attempt a high-quality periodic error correction curve. But as I said, I don’t see anything “wrong”, just things than can probably be refined with a bit of effort.
FWIW, I’ve read that the Colorado Front Range is often plagued by poor seeing conditions, so you should probably keep that in mind when you’re setting your own expectations for guiding results.
Good luck,
Bruce
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Patrick Spencer
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bw_msgboard
Sure thing, Patrick. It will take some careful reading and a bit of time to get a high-quality PEC curve programmed but it is usually worth the effort.
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Brian Valente
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