New AP1100 Guiding Great on Very Windy Night

Mark Lamb

Last night, my new AP1100 (base) peformed great on very windy night.  I got the AP1100 a couple of weeks ago, and I am very early on the learning curve.  Per George's recommendation, I have yet to try any of APCC modeling, and using it just as I would my G11.  I was imaging with a tiny scope, Vixen FL55ss at 237mm, f/4.3, and using my QHY268M capturing the Question Mark nebula in narrowband, using 8 min subs.

A couple nights earlier, I tried using an old ST80 (just purchased) as a guidescope, but the results were not that good, even though PHD2's total RMS was in the 0.4-0.5" range.  I had to throw out ~40% of the subs for eccentricity.  I did not know if the issue was the night's bad seeing (~2.9" according to MeteoBlue; the worst I had encountered in 3 years) or the long focuser cantilever on the ST80; I had to add ~100mm of M42 extensions and rack the focuser fairly far out to focus.  Previous attempts with a generic 60mm/240mm guidescope did not have eccentricity issues, though sky conditions were much more typical at ~1.5" seeing.  

My 1st attempts using the AP1100 with a generic 60mm/240mm guidescope was similar to my G11 guiding with OAG, but more consistent.  It is nice to have practically zero backlash compared to my G11's ~800ms typical (400-1200ms range).  My only disappointment so far is the single bad night using the ST80 as guidescope, but I do not think the AP1100 had anything to do with the bad results.

With the single night's bad experiment with ST80 guiding, I decided to use a QHY OAG instead of guidescope.  Even with the bad wind conditions, PHD2's total RMS was in the 0.2" range, and I only threw out 1 of 60, 8 min subs, and the sub that I deleted was not that bad.   Even though it was very windy, the online seeing estimates were in my typical range at ~1.4".  So here on, I will be using an OAG even on my very short FL scopes.

I know I benefited from the very tiny FL55ss lack of much wind surface, but I had to add much to get it balance in DEC, as well as balance in RA.  I am glad I got the 10" combo saddle instead of the larger saddle, as this tiny scope train gets very back heavy with OAG/CFW/QHY268.  I end up mounting the FL55ss on back end of a 14" DUP using a camera mount clamp, with additional pair of ~140mm CNC rings with 8" Vixen bar on top (very forward on DUP) with heavy Vixen clamp on the Vixen bar and Losmandy D clamp attached to the underside of the DUP.  For AP, I guess one can never have enough additional clamps, bars, tubes, etc....

I am very please at how the AP1100 without encoders handled last night's windy conditions!

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