Mar 28 2026 APP 2.0.0-beta40 will be released in 7 days.
It did take a long time to have the work finished on this and it will have a major performance boost of 30-50% over 2.0.0-beta39 from calibration to integration. We extensively optimized many critical parts of APP. All has been tested to guarantee correct optimizations. Drizzle and image resampling is much faster for instance, those modules have been completely rewritten. Much less memory usage. LNC 2.0 will be released which works much better and faster than LNC in it's current state. And more, all will be added to the release notes in the coming weeks...
Update on the 2.0.0 release & the full manual
We are getting close to the 2.0.0 stable release and the full manual. The manual will soon become available on the website and also in PDF format. Both versions will be identical and once released, will start to follow the APP release cycle and thus will stay up-to-date to the latest APP version.
Once 2.0.0 is released, the price for APP will increase. Owner's license holders will not need to pay an upgrade fee to use 2.0.0, neither do Renter's license holders.
Hi,
I keep noticing that I get this error message, as per this thread: https://www.astropixelprocessor.com/community/main-forum/critical-warning-flat-field-calibration-can-not-be-performed-correctly-2/
My flats and dark flats are actually created by the same plan! One with the scope covered, one not. The gain, offset, duration etc are, by definition, identical. So, how is this possible?
Furthermore, this happened today, and out of curiosity I just started the integration again - and now the message hasn't appeared.
In the past I've worked around it by creating the masters in a separate integration, but I don't like 'workarounds' and I don't understand why this is happening.
It sort of wouldn't matter I guess, if the final image popped out OK. However, I'm having a heck of a time trying to get decent results from my new ASI1600, and this is just one of several issues I'm trying to iron out.
Can anyone shed some light on this please?
Thanks, Brendan
Just to confirm, you are running the latest version of APP?
Hi Vincent, Brendan;Â
I was getting the same message under 1.083.2 (MacOS), which is the latest version.
I just diregarded by clicking OK and calibration went fine. I had different ISO & exposure times for Lights/Darks vs Flats/Darkflats though, while Flats/Darkflats were the same ( just as in Brendan's case) I suspect, APP is compairing Lights vs Flats / Darkflats hence complaining, but this would not be valid. Can you confirm?
Cheers,
Jochen
Just to confirm, you are running the latest version of APP?
1.083beta
@brendan What data do you get this warning with? Narrow band or wide band or OSC? You only indicate that you're using an ASI1600 but not if it is mono (MM) or color (MC). What exposure time do you use for the lights?
The warning is shown when APP detects that pixels are clipping to zero in the lights after applying the calibration files. When the warning is shown, you can switch to the console window which will tell you exactly how many pixels are clipping. What number do you see? Mind, you'll need to use the latest version of APP, not the beta. So please upgrade to 1.083.4 (Windows) or 1.083.2 (Linux and Mac).Â
I suspect, APP is compairing Lights vs Flats / Darkflats hence complaining, but this would not be valid. Can you confirm?
This is not exactly correct depending on how you interpret "comparing". APP applies the calibration files to the lights and then detects that some pixels in the lights are clipping to zero. The warning is shown when 100 or more pixels clip. Usually this indicates a too short exposure time for the lights. In any case, the warning certainly is valid.
@wvreeven OK, I just upgraded and will take another look tomorrow. Thanks for responding.
The data was broadband, and the flats were between around 1.3s for the L, 5s for the R and G, and 2s for the B. The lights were 60s for the L, and 180s for the R, G and B.
The message is quite confusing however, because it doesn't mention that clipping is an issue, it just says that there are differences in the flats and dark flats, which there really were not.
I also don't understand why it was then possible just to run the stack again and it worked?
When the warning is shown, you can switch to the console window which will tell you exactly how many pixels are clipping.
I can't switch to the console! There's just the message, with the OK button on it, and no way to switch to the console that I could find.
I clicked OK and then stopped the processing anyway, and this is the last few minutes of the log. I can't see any mention of pixel counts?
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Hi Wouter,
when Darks get applied to the Lights, isn't "Adaptive Pedestal" designed to prevent them clipping to zero?
wouldn't that be a solution to prevent this error? Also, If it was clipping to the LSB instead of zero, Flat Calibration would still be valid.
Also, the BPM should remove any Dead pixels in the lights prior Flat Calibration, so how comes there are so many left? Should we lower the dark Kappa value?
Thanks,
Jochen
I clicked OK and then stopped the processing anyway, and this is the last few minutes of the log. I can't see any mention of pixel counts?
Unfortunately not. You'll need to scroll up in the console to see the number of clipped pixels.
when Darks get applied to the Lights, isn't "Adaptive Pedestal" designed to prevent them clipping to zero?
Yes it is and APP makes a sensible estimate of the pedestal to apply. If then still at least 100 pixels clip, the warning is shown. Without the pedestal, probably tens to hundreds of thousands of pixels would clip.
What it boils down to is this: the master dark has a mean value and a standard deviation. The standard deviation is there because of the natural, statistical fluctuations in the dark current. When the master dark and the pedestal get applied, all pixels are supposed to have a value larger than zero. In some (and potentially too many) cases it is not which indicates that the lights have not been exposed long enough.
Also, If it was clipping to the LSB instead of zero, Flat Calibration would still be valid.
Correct, but as explained the pixels actually clip to zero.
Also, the BPM should remove any Dead pixels in the lights prior Flat Calibration, so how comes there are so many left? Should we lower the dark Kappa value?
Yes, in such a case the kappa value should be lowered.
OK, well, I just reloaded all the data, expecting it to show the warning again so that I could look at the log, and it's gone right through to star analysis no problem. I don't understand this.
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