[Craig_]

I got my gear out tonight for first time in months (which was a mistake in hindsight as it was an incredibly damp night) and tonight was my first night to use the ASI Air Plus I got last November (!). Bloody cloud. Anyway, I really struggled with the polar alignment routine.

I have historically always used Sharpcap's polar alignment routine and never had any issues with it. Always able to dial in P.A with incredible accuracy very quickly. Tonight I did the usual - put the tripod down, level it, make sure it's pointing true south, etc. Boot up the ASI Air, at first P.A seems to work OK - it platesolves the initial image, adjusts by 60 degrees and platesolves again, and reports my error to the SCP. All OK so far. But then it just went off the rails after that.

It would tell me, for example, I had 10 degrees 14 minutes 27 seconds error on the azimuth and say 25 minutes 10 seconds error on the alt (these are just rough numbers but are approximately what it was reporting.) I would dial in a small adjustment in the direction it was telling me to, platesolve again and see the error improve - great. But pretty quickly I got to a point where continuing to dial in corrections on alt/az broke platesolving - as though I'd overcorrected - even though it was still telling me to keep correcting in a particular direction prior to it breaking. I was only making small adjustments; I am no newbie to polar alignment having done it in sharpcap countless times. I later figured out that I had to make say a small adjustment on alt, then a small adjustment on az, then alt, then az, etc, and that worked for a while, and then despite still reporting ~8 degrees of total error, got to a point where continuing to make even tiny adjustments on either axis in the directions it was telling me to just broke platesolving.

Any clues what I was doing wrong? At face value it seems to work much the same way as Sharpcap, except in SC I like that you get a continuously updated feed of what you have captured for each PS on screen and it includes arrows showing where you are relative to the SCP - it makes it very hard to go in the wrong direction or overcorrect dramatically. As far as I can tell ASI Air does not offer an ability to actually live view your platesolved images and just shows where you are relative to the SCP on a x/y axis.

If the night hadn't been so unbelievably wet I'd have plugged my laptop in and PS'ed the old fashioned way but I packed up as my gear was already drenched by 7pm. But I'd like to understand where I went wrong with the ASI Air for next time, as aside from this PA snafu it seems like a really impressive device.
Cheers