lock042

Yes and we have made tests with this camera.

In your case, you do use sensor not cooled and with a lot of glowing. As we said in the post. We encourage users doing tests before as we are speaking about modern sensors. For example, what I'm saying is TRUE for modern DSLR. Try to make a 60s dark and a bias with a DSLR. Level is the same. Astrophotography evolves, sensors too.

It's look like you have some leak of light... Here an example of 294MC non cooled, It is less stable but not like you: Shot with sharpcap

Do you have your offset set to 0???

@vlaiv: just to make sure. We are talking about modern CMOS sensors. As we explain in the post it is not true for old CCD sensor where the bias could contain linear gradient

It contradicts common beliefs. But it is normal and this is why I encourage people to make tests!! The dark at 300sec come from the 294MC and NINA: 23:58:12: Reading FITS: file DARK_300s_G120_O30_T-10C_bin1.fit, 1 layer(s), 4144x2822 pixels 23:58:17: Running command: stat 23:58:17: B&W layer: Mean: 1922.3, Median: 1919.0, Sigma: 125.5, AvgDev: 4.9, Min: 1862.0, Max: 65532.0 Others example come from 294MM. In the post we did not show dark with longer exposure of 5s because it was not the purpose of the post.

yes

Mean is a non robust estimator. Median is a better one. Here you have what you want. The level of a master dark at 5sec you can compare with the previous image: Then in the the table here you can see median evolution:

This not because you will repeat it's wrong that is really wrong :).

Yes. Example in the post are done with 294MC. And dark of 300s has same level than bias, except in the ampglow flash

You're right, but in your example you take a flat underexposed and a very high dark current to best match what you are saying. Anyway, I take the example of a basic non cooled camera I have: Canon EOS 100D. level of bias: 2048 (2^11). level of dark (60s) : 2044. It is the same especially when you compare to the flat. Then in this case take a constant that correspond to the value you want. We encourage users to test it. I'm sorry but it works, and it works well. Saving process time and disk space. Because yes, this is not a issue of noise. Did you read the second link I gave you?

Or just a constant. You can't beat it. Wrong. We wrote a tutorial here: https://siril.org/tutorials/synthetic-biases/#appendix-understanding-how-the-flats-correct-the-lights if you want to take a look. The appendix details computation. Absolutely not. The most important in the process is the level you subtract to the image to have a proper calibration of data (and offset has same level than dark, you can check by yourself). Just test it and you will see. And please, post the results here.

In fact that depends more of your ampglow (do you see ampglow flash in your masterflat?). Take a look at our figure 3: even if you do have some thermal signal you don't care. Don't forget your flat is full of light and the thermal signal is not a problem like it could be with your light frames.

From a pure noise point of view, dark flat adds more noise as we show in the link. However, it is probably negligible. But why make unnecessary frames when you can avoid it with synthetic biases?

Hello, Behind this provocative title we have wrote a post about dark flats. Indeed, more and more, I see the term master dark flat all over the forums and I would like to explain why you shouldn't do it. This is here: https://siril.org/2021/12/enough-with-dark-flats/

That should always be applied on linear image.

In fact, Siril if is free (as in beer), it is, above all, free (as in speech). And if fact, it is not really free (as in beer), because users are invited to make donation (of course, only if they want) but it is a kind of price. Really nice picture btw. I like it.

Hello. We have a great tutorial that explains everything in appendices on how works the flat correction, and why in some cases, you over-correct it: https://siril.org/tutorials/synthetic-biases/#appendix-understanding-how-the-flats-correct-the-lights

@Somerled7: https://siril.org/faq/#how-can-i-combine-different-exposures-on-the-same-object

This is because we never should try to stack different exposures in sametime... DSS is doing that, that's right. But for me this is a big mistake. You need to stack consistent frames. So, stack each exposures to produce different images. And then, merge the image withing GIMP. I guess you shot M42.

Oh and looks like you use an old version of Siril.

Hello. In Siril you can remove the background on each light. It is really better than removing after stacking.

Thank you so much for the feedback :). Yes we have worked a lot on the new website and tutorials, so very happy you like it!

Hello. With the release of the new version of Siril (0.99.8.1) we have updated our website at www.siril.org. Also, we have updated a lot of tutorials especially one that should really help beginners!! You can have a look here: https://siril.org/tutorials/tuto-scripts/ Please, do not hesitate to share it, and to write feedback.

The new website is : https://www.siril.org ;).