lock042

@Spaced Out: a positive answer could help all the community :).

Hello @Spaced Out. As indicated in the topic, you need to check the dither option. If you made a stack with Siril, in 32bits mode, you wouldn't have needed it, though. In order to improve the documentation, could you send me your stack output image (WeTransfer), and give me the rights to use it for the Siril documentation?

Yes this is allowed. Siril is free, open source, under the GPL3 license terms.

Please update. This behavior will disappear.

Ok. Sorry but I stop here. This assertion is so wrong that I couldn't go further. Have a nice day.

We are talking about removing dark flat to flats. We don't care about light pollution. This is my whole point. We are just talking about flats here. Of course darks are very important to remove all unwanted signal to light frames.

Be careful. Your ampglow can be negligeable at 1.8s, like with 294MM. If you look your image very stretched, of course you will see it, but statistics don't lie.

Everything is explained here: https://siril.org/tutorials/tuto-manual/#background-extraction

Did you tried to remove background on each sub? It works pretty well. Siril works only with monochrome or CFA flats.

To change working directory you can use the "home" button at the top.

Try relative path. I know it works in script mode.

Could you send a screenshot please?

Symlink do work with windows development mode on. But conversion does not change pixel value.

Uncheck the "normalize output" button.

OK, what you were asking for before is not the test you have been doing, as nowhere in your procedure you were asking to subtract a master. What I gather from your experiment is that: First line is the stats of a single bias Second line is the stats of same bias with a constant value subtracted Last line is the stats of same bias – a masterbias. Fair enough, it makes “more sense”. At least if the discussion from the start had been about calibrating biases… which is not at all the point. So here is the test that we have been talking about. Made 200 darkflats of 0.9s, matching the flats done for a session from last summer. ZWO ASI294MC, gain 120, offset 30, T -10C for reference. Stacked 1, 10, 25, 50, 100, 150 and 200. Yes, of course, the std decrease with increasing subs… Then checked the stats of a flat (1st CFA channel only, it would not make sense on a color sensor to measure all channels altogether) from which I have substracted a synthetic offset of 1920 and masterdarkflats made with 50, 100, 200 stacked frames respectively. And here-below the results: I’m not even going to claim that there is significant reduction in noise in the calibrated flat, because the stds are probably within the uncertainties. But to be honest, this kind of measure is the basis for questioning the usefulness of using darkflats (or bias) to calibrate the flats. I hope this will encourage others to test with their setup. So now I think we've done enough testing (here and with the post). We're not forcing anyone to adopt synthetic bias, but we've shown in different ways that it's worth a try.