27 hours on M27

[DaveS]

and rechecked my flats, it's only the first sub of the list that is zero seconds, all the others are 2.0 sec like the dark flats.

[DaveS]

Here is a single unstretched Oxygen flat

Flat-0021O.fit

[andrew s]

15 minutes ago, DaveS said:

OK, just checked the capture setting, and it was set to 16 bit, so that source of error is cleared up.

What offset are you using on the camera? Regards Andrew 

[DaveS]

According to the ZWO ASCOM driver it's set to Offset 10. Too low?

[andrew s]

6 minutes ago, DaveS said:

According to the ZWO ASCOM driver it's set to Offset 10. Too low?

Yes at your gain you have a read noise of 3 to 4e rms with a gain of 5 e/adu giving 15 to 20 adu rms. Try something like 50 to 60. Check you darks are not clipped at zero but show a good gaussian like distribution .

Regards  Andrew 

[DaveS]

The Darks are showing a comb-like gaussian distribution with a min ADU 0f 163

[andrew s]

20 minutes ago, DaveS said:

The Darks are showing a comb-like gaussian distribution with a min ADU 0f 163

I suspect  the comb is due to the quantisation noise I mentioned above. I run my ASI 1600mm with 16bit raw gain 139 offset 50 bandwidth 80.

Regards Andrew 

On second thoughts it may be the stretch from 12 to 16bit that causes the comb.

Edited October 7, 2020 by andrew s

[DaveS]

7 minutes ago, andrew s said:

I suspect  the comb is due to the quantisation noise I mentioned above. I run my ASI 1600mm with 16bit raw gain 139 offset 50 bandwidth 80.

Regards Andrew 

OK, the bandwidth is 80, and the gain zero but the offset is 10. The files are 16bit raw.

[andrew s]

Dave here is a very short dark of mine 0.5s You can make it looked combed if you stretch it enough. Regards Andrew

Regards Andrew

[Laurin Dave]

52 minutes ago, andrew s said:

Dave here is a very short dark of mine 0.5s You can make it looked combed if you stretch it enough. Regards Andrew

Regards Andrew

Same for mine on individual subs but the Master Dark created from them is fine...  If the minimum ADU in your darks is 163 then therein lies a problem as the minimum ADU on your Oxygen sub is 48..  so if you calibrate without a Pedastal there will be Black clipping ...  I don't understand why your Dark minimum is so much higher than your Light minimum , the FITS header gives no clue as it doesn't show the Offset.

Anyway here are two calibrations of the raw Oxygen sub..   the first using the Dark posted above with no Pedastal and the second using the same Dark but with a Pedastal of 250 (which gave a minimum value of 2)... No flats....  the second one looks pretty good to me and 9 hrs of that ought to give a cracking Master, clearly best to do with the matching Darks you are generating.  Your filters are impressively clean - but best to use them because of the ASI1600's checkerboard pattern.

HTHD

Dave

 

Dave

[DaveS]

OK, I was wrong about the minimum ADU, re-reading the hiso it runs from 114 to 450 odd.

How do I add a pedestal in AA? Or can I do it in <axim during capture.

Damn, I should know these things, I've been imaging long enough.

[andrew s]

30 minutes ago, DaveS said:

OK, I was wrong about the minimum ADU, re-reading the hiso it runs from 114 to 450 odd.

How do I add a pedestal in AA? Or can I do it in <axim during capture.

Damn, I should know these things, I've been imaging long enough.

Learning is a life long process and at my age relearning is now dominant. 😱

Just to be clear, if your lights were exposed at the same temperature and exposure as the lights then they should have a higher mean level (I know you had temp difference). If they don't  something is wrong. I always take darks in the dark and telescope covered to avoid light leaks.

Don't use scaled darks with CMOS as amp glow is nonlinear with time and the different (short v long exposure) readout modes can cause issues with bias frames.

Regards Andrew 

Edited October 7, 2020 by andrew s

[DaveS]

This is the stats for the 12 sub stack I've just done of my -20C Darks

Hope this makes sense to someone.

[andrew s]

6 minutes ago, DaveS said:

This is the stats for the 12 sub stack I've just done of my -20C Darks

Hope this makes sense to someone.

Looks reasonable once I realised the second bit after the min and max were coordinates.

Can you post the histogram stretched similar to mine so we can compare them?

Regards Andrew 

[DaveS]

I'll try, but I think AA is very different to PI

[andrew s]

Ok post the file and I will do it in The Sky X as I did for mine.

Regards Andrew 

[Laurin Dave]

1 hour ago, DaveS said:

 

How do I add a pedestal in AA? Or can I do it in <axim during capture.

 

Its in "Options"..  "Filters" .."Add Pedastal"  

[DaveS]

10 minutes ago, andrew s said:

Ok post the file and I will do it in The Sky X as I did for mine.

Regards Andrew 

Thanks Andrew, here it is.

12 sub -20C Stack.fit

[DaveS]

7 minutes ago, Laurin Dave said:

Its in "Options"..  "Filters" .."Add Pedastal"  

Thanks, will check Maxim, though I think ASA Sequence only uses Maxim for the camera control.

[Laurin Dave]

5 minutes ago, DaveS said:

Thanks, will check Maxim, though I think ASA Sequence only uses Maxim for the camera control.

That's in AstroArt..

[DaveS]

OK, thanks. Found it.

[andrew s]

Here it is stretched as mine. The second peak is, I suspect, the amp glow and hot/warm pixels appearing as expected. Looks ok. Regards Andrew

 

[DaveS]

Thanks for confirming that Andrew.

[andrew s]

This compares the O2 and the dark they look compatible to me.  Similar background etc. Regards Andrew

Edited October 7, 2020 by andrew s