Astap solve failure after meridian flip

Hi - this is the first time I have been able to use my kit since November 2020. Just persistent cloud. Trying to keep positive.

Anyway, imaging M82 tonight and folowing a meridian flip at around 10.50 local time, ASTAP would not solve folllowing the flip. The sky was clear and lots of stars in M82 region. I switched to Platesolve2 and got a solve in under 1 second.
Anything I can do to improve reliability with ASTAP?

My setup uses the G18 catalogue, a celestron C14 and 0.8x reducer with an SBIG stt8300M camera

fov is roughly 25 x 20 ish arcmin

thanks for any help. It would be even greater help if someone can solve the weather…

The FOV is small. It could be the numbers of stars visible or the binning.

For a FOV of one degree an exposure time of 5 seconds is fine but 25x20 arcmin is 7 times smaller area. Just expose longer, 20 or 30 seconds.

Keep also binning low, not more then 2x2.


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Paul, my fov on my main scope is bigger than yours at about 50x70 arc mins and I image at F/5. ASTAP works with a 5 second image at 2x2 binning and the only time it has failed has been because of clouds or my stupidity! But I guess if you are imaging at F/8 or F/10 then, as Han suggests, doubling, tripling or even quadrupling the exposure time might be needed to get a decent signal. Odd that it’s only after the meridian flip though.

thanks for replies, most of the time things work fine, I just get odd occasions where ASTAP can’t solve. I appreciate my small FOV as a galaxy imager is potentially a problem, so I’ll try increasing the exposure time. Presumably the effect of that will be that the image will be deeper and include some fainter stars for use by the algorithm.

Just thinking out loud, would it be a useful new feature for SGP if there could be an option for us small FOV folks to say increase Platesolve exposures by a factor which we could choose in the equipment profile e.g 1.5X or 2x and this choice would become active if a plateslve failure occurs? This would optimise platesolve time, so e.g. in my case I would say that solves work > 95% of the time so I could keep my current 12 sec exposure. If PS fails, then the option kicks in.

The reason I think this would be good is expecially for unattended solves which have the potential to terminate an imaging session. Personally, Since March 7th 2020, I have only had two sessions due to cloud cover or bright moon and these two were both in late March 2021 - a nearly 5 month gap between imaging sessions. Increasing cloud cover seems to be a trend. So from my perspective (and many others I guess) anything which helps to keep a rare imaging session alive is welcome. What do you think about the idea? If it’s viable I’ll put it in a features request post.


Paul. I’ve just remembered another reason for plate solve failures, and the is the mount settling time. I think I’ve now set my EQ6R-Pro at 15 seconds otherwise I can occassionally get streaks rather than stars and ASTAP doesn’t like that (none of them would to be fair). You may already have this covered, but it was just a thought. Terry

thanks Terry, I have a MESU 200 roller mount, so had my settling time at 5 seconds, i’ll try increasing that - perhaps might be able to get an idea of how long is required from a PHD2 graph…