stacking/darks quer

[muletopia (Chris)]

Learned folk,
I have an hour of 5 minute shots of Helix. Gain 0 offset 125 qhy8l

I have a matching set of darks,that have been debayered then stacked to make a master dark.
When stacking the debayerd shots in Nebulosity without the darks used a recognisable image emerges.
If the shots are preprocessed and then stacked all trace of Helix vanishes.


I have used preprocess shots on other images with good results. ,my M55 image on this forum seems OK


I presume I doing (not doing) something wrong.
I hope there is a simple reason for this problem, any help would be much appreciated.


Cheers
Chris

[h0ughy (David)]

Don't use nebulousity however is the Bayer matrix set up correctly

[Sunfish (Ray)]

I find nebulosity stacking a bit difficult . Have you tried stacking the darks and lights in DSS and the opening the unchanged fits in Nebulosity just to see if there is a problem with the darks?

[glend (Glen)]

Use DSS, I have never had a problem with it.

[muletopia (Chris)]

Thank you for the replies.
Considering them I suspect that the darks are at fault, so when I get home tonight I will take another set of darks. If that does not solve the problem I will download DSS


So, thank you



Cheers
Chris

[Startrek (Martin)]

I’ll second everyone
Use DSS and don’t fiddle with the final stacked file (Keep data linear)

[middy]

Don't debayer the darks before you stack them to make the master dark. I stack raw darks to make master dark and then I use it to pre-process my raw images. Then I debayer the results of the pre-processing step.

[multiweb (Marc)]

Do all calibration darks, flats and bias before debayering including making the masters.

[muletopia (Chris)]

Martin, my stacking program of choice is Siril.


Middy, I will do as you say and look at the results, this may be my problem and hence the Ah Ha



Marc I think you mean the same as middy.


Any way the camera is now busy taking 20 5 minute darks, Craig Stark is clear on the advantages of stacking many darks.


Thank you for your replies gentlemen.
Slowly slowly I may learn.


Cheers
Chris

[multiweb (Marc)]

Originally Posted by muletopia

Marc I think you mean the same as middy.

Yes. Debayering to color is the very last thing you do just before stacking your light subs. So in order:

1_ stack your flats/darks/bias frames without aligning them to create your masters.

2_ calibrate all your light subs with the masters.

3_ debayer your light subs and stack.

[muletopia (Chris)]

Martin... I have installed DSS, now need to learn to drive it.
The newly acquired darks have been used. These comparison pictures were stacked with Nebulosity.

The first attachment is created by following Marc's instructions.
The second attachment was created by
stacking the debayered darks and pre-pocessing the debayered lights the stacking the pre-processed debayed lights.
I do not think that there is any significant difference.


BUT both methods appear to fail to remove hot pixels (and say that I should do another polar alignment).
Why the ho pixels are not removed I don't know.


12 5 minute lights used

20 5minute darks used


The Siril stack gives much tighter stars but not needed for this comparison.





Chris

[muletopia (Chris)]

sorry I did not put them in the last postChris

[muletopia (Chris)]

thir time lucky?