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!

Christopher M

Nice.  Thanks for the comments Mark.  Let me/us know when you put a longer package on the 1100.
Myself I'm working with a new Stowaway on an old G11 Digital mount and waiting until I can swing an 1100.  It too is windy here on the prairies.  My friend put his RedCat w ST-8300/FW8 package on his AP900QMD and it is a rock, which is no surprise.

For comparison tonight it is far more windy than anticipated.  Average is about 7mph, erratic, gusts to 20-23mph.  My 1100AE is carrying a 4" refractor so not a big sail like my C11 would be.  So far I'm running at 0.67" RMS with peaks at 1.4/1.48" and the stars are round at 100% (not completely so at 200%). 

The graph looks awful compared to a calm night, but it is coping reasonably we.. 

Here's what the wind has been like since I started: 

That's measured about 3' off the ground beside the scope.  Here's a small crop at 100% (1.4"/pix scale): 

I don't know how much of this is the encoders reacting, how much is just that it is well built, but very happy.  I got the encoders to do better in wind (since our dry season is more windy than the wet, ironically). 

Very happy. 

Open to suggestions of guiding parameters for wind.  I think I'm chasing the wind tonight with the settings, frankly, but hoping it will die down.  Normally I get around 0.2-0.25" average at 3s intervals. 

Wind is still the enemy, but I am more prepared than I used to be with the new AP mount.  Thank you!