What would be an acceptable image rejection rate?

Draco

The past 10 days I imaged almost every night with, for me, disappointing results. At best I could achieve 55% rejected images on an object but most of the time the percentage would lie between 75 and 85%. That resulted in an imaging night of say 7 hours getting me 75 minutes of data! That can't be right, can it? And all that because stars becoming stripes and the image is rejected. What to do; send it back?

starnet

Draco Welcome to my world. Yes, leveling, low azimuth, wind and so on will influence the image rejection rate, but what I do not get is this - during a single, say 30 minute session, pointing to the same target, no wind to speak of, the S50 alternates about every few minutes or so between almost 100% success rate and maybe just one 10 second frame out of five. On average, I was never able to achieve more than 50% stacking success rate on exposures longer than 5 minutes or so. And it is also firmware dependent, I got my S50 in December last year and I vaguely remember much better success rates in the spring than what I am able to achieve now.

satch984

1 on 3 rejected is ok

Max-OP

Stay away from the zenith. The frame rate rejection is much higher there, that is just a fact of an Alt-Azimuth mount. Shorter (10) second exposures will yield lower frame rate rejection as there is less chance of tracking errors. I experience very low frame rate rejections by following these guidelines.

xfirf

Check if you can avoid shaking through wind or check the table / place where it is placed to be strong enough against vibrations and see if it helps. Also try not to extend the legs to be more stable.

support

Hello, I am very sorry for the unpleasant experience.
Seestar stack failure, which is related to many factors, such as wind, ground vibration and other environmental factors.
If you shoot the target near the zenith, then the field spin will be more serious, which is also easy to lead to stacking failure.
It is also recommended that you use the default exposure time of 10 seconds, longer exposure time will easily cause the star to be stretched out.
Finally, it is recommended that you check the level of the equipment.
I hope I can help you.

LA3QMA

support Is it possible for you to post the work logic on how the current firmware is deciding on how/when to drop frames? I guess some feedback from many of the more experienced users in this forum could give the developers some ideas if its possible to make this more robust.

Simplesimon

starnet

I have the same issue sometimes, but not always. I think it moves the arm a fair distance every five subs for dithering, and because the gears have so much slop, it takes a while for the slack to be taken out.

This phenomina also appears to be affected by the location of the target in elevation and azimuth.

Maybe someone from ZWO could confirm this?

altazastro

If only they would let us save ALL the frames (as it was briefly possible with an experimental feature ages ago), then one could stack them offline and achieve higher rates. Offline stacking is bound to work better: I mainly use Astro Pixel Processor and it is relatively slow but very efficient, while realtime stacking, moreover running on the limited CPU and memory of the S50, clearly produces a higher frame drop rate.
I asked ZWO more than once to reinstate the possibility of saving all the frames, but so far to no avail ... and I do not believe it is all that difficult!

marvindj

altazastro

"Offline stacking is bound to work better".

Just curious what you mean by "better"? I'm newish and have been searching for a generic description of the stacking algorithm.

Do you mean offline would be "faster" given additional hardware resources which may be available? Do you mean the stacking algorithm implementations would be "better" resulting in a final FITS file with more accurate representation than the S50's stacking implementation can generate?

If by chance you have a link to an algorithm description, I'd really appreciate the pointer.

Thanks

stormynorm

Last week I was imaging at a spot under a very busy airway, when T CrB was aligned with it the unit was dropping a lot of frames. Went to M16 for a while then back and it was fine.

starnet

I have been taking a lot of 10 minute exposures attempting to create my own wide field mosaics since ZWO is taking their time to come up with this feature. On average, it takes 15 minutes to take a 10-minute exposure.