question about multiple sessions

[Clarkey]

I would agree that out if all calibration frames, flats are most critical. But if you take flats you might as well takes dark flats as most software will easily do both. Darks can be done at anytime so it makes sense to do them for cooled cameras. Bias frames are easy so no excuses there. Therefore you might as well do all of them😁. Jobs a good'n.

[StuartT]

6 hours ago, tooth_dr said:

You have some nice data there, and without calibration data looks good.  You have some badly out of focus stars at the top of the image so I wonder did you keep a dodgy sub or two?

Personally I find calibration frames (dare I say it) essential for post processing.  I dont think you are dithering either between exposure - there is some walking noise evident also in the images - I find calibration really helps here if you prefer not to dither.

Are you taking your flats correctly?  If you are getting such negative impact with the flats is it possible that your arent taking them correctly or if you are taking them correctly then the focuser and or camera has moved between taking them and the lights?  Light leakage would be something else to look at.  I can see how it would appear that on the surface calibration data is doing harm, but I dont think I've come across a situation where it's harmed my data (talking specifically about set point cooled data, as with DSLRS its different) - unless the calibration data was wrong ie temp, duration, wrong camera data used etc.

What do you think?

thanks.

I think the flats were shot ok. I used the flat wizard in NINA. But they were from a diff session with the camera removed in between. So I guess they didn't match well.

[ollypenrice]

2 hours ago, Clarkey said:

I would agree that out if all calibration frames, flats are most critical. But if you take flats you might as well takes dark flats as most software will easily do both. Darks can be done at anytime so it makes sense to do them for cooled cameras. Bias frames are easy so no excuses there. Therefore you might as well do all of them😁. Jobs a good'n.

I'm not sure that bias are useful with CMOS cameras...  They certainly are with CCD, however.

Olly

[StuartT]

And presumably, darks can just be built up into a library (provided the temp and gain matches)?

So only really flats and dark flats need doing then and there (before dismantling the rig, I mean)?

[x6gas]

21 minutes ago, StuartT said:

And presumably, darks can just be built up into a library (provided the temp and gain matches)?

So only really flats and dark flats need doing then and there (before dismantling the rig, I mean)?

You can indeed build up a dark library and re-use them for a good long time (a year or more - cameras do evolve and get more defects).  Some software (PixInsight for example) will adjust the way darks are applied to compensate for different exposures etc but I prefer to take matched darks still.

Now that said, today's cooled astro cameras are so quiet that you can definitely get away without using darks and just using hot/cold pixel correction in software.

Using flats was probably the single thing that improved my images the most even though.  I tend to cheat though:  I make sure everything is super clean so I take flats with an EL panel and reuse them.

[Clarkey]

28 minutes ago, StuartT said:

So only really flats and dark flats need doing then and there (before dismantling the rig, I mean)?

Yes.

 

51 minutes ago, ollypenrice said:

I'm not sure that bias are useful with CMOS cameras

I was talking about DSLR's really, where they are more beneficial without fixed temperature darks. I would not bother with them for cooled astro camera's

[StuartT]

4 hours ago, x6gas said:

You can indeed build up a dark library and re-use them for a good long time (a year or more - cameras do evolve and get more defects).  Some software (PixInsight for example) will adjust the way darks are applied to compensate for different exposures etc but I prefer to take matched darks still.

Now that said, today's cooled astro cameras are so quiet that you can definitely get away without using darks and just using hot/cold pixel correction in software.

Using flats was probably the single thing that improved my images the most even though.  I tend to cheat though:  I make sure everything is super clean so I take flats with an EL panel and reuse them.

 

4 hours ago, Clarkey said:

Yes.

 

I was talking about DSLR's really, where they are more beneficial without fixed temperature darks. I would not bother with them for cooled astro camera's

oh wow! this is great! so now it sounds like I can dispense with both bias and darks (as I have a 2600MC Pro). So I really only need to do flats and dark flats. 

Excellent!