Astropixel Processor - Critical warning flat field calibration

[BrendanC]

Hi all,

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

Edited April 2, 2022 by BrendanC

[symmetal]

I always create the masters separately as I reuse the flats many times until new dust spots become noticeable so haven't come across this issue.

When you receive this error it's worth checking the file listing at the bottom of the APP screen to confirm that the correct flat darks have been assigned to the correct flats, (and in the correct session if multiple sessions are being integrated).

I use the automatic assignment feature of APP when loading files, which requires the frame type and filter to be correctly identified in the fits file header. In the past I've taken flats while mistakingly labeling them as lights in the capture program, so requiring manual assignment in APP.

As your integrations work some times and produce the error on others, I can only think that the assignments are different. I assume all the APP integration options are the same each time. I find it a bit annoying that default option settings are applied each time you start APP and any different options you want have to be set every time. Also the working folder has to be changed from 'Documents' every time. 

Alan

[BrendanC]

3 hours ago, symmetal said:

I use the automatic assignment feature of APP when loading files

I haven't heard about this. How does this work? I must say, without a user guide, APP is not the easiest package to get to grips with...

[symmetal]

2 hours ago, BrendanC said:

I haven't heard about this. How does this work? I must say, without a user guide, APP is not the easiest package to get to grips with...

When you load your image files instead of clicking the channel they correspond to just have the 'apply filter Header tag...' box ticked as shown below. It will then assign the files to the correct channel depending on the information stored in the fits file header. This is quickest if all your lights are in the same folder, all the flats are in another folder, so one click will load all the lights selected, another click loads all the flats selected. For darks they still have to be assigned to the relevent colour channels as you've been doing as there's nothing in the fits header that says which channels they will correspond to. Dark flats will auto allocate if there is sufficient fits header info.

I also use master flats, darks, and flat darks previously created with APP and the master flat darks fits headers are labelled such that they can be auto sorted to channels.

You can have all your lights, flats, and possibly flat darks in the same folder and APP will assign them all with a 'select all' and a load click, but this can be a bit awkward to manage and keep track of what's what.

Thinking about it, although I haven't tried it, it may also be possible for darks to be auto assigned too, if the exposure info in the darks fits header can be matched to the exposure info in the lights. Whether APP does this I don't know. Will have to try. 

Alan

 

[BrendanC]

Interesting, thanks!

[tomato]

Much as I applaud the software authors who provide automation of file loading and assignment, I’ve been caught out too many times to put my faith in them. As I am fortunate to have the time to do this, I load all my lights and master calibration files separately and manually assign them in APP. Takes a bit more time certainly, but no head scratching should a processing warning arise.