California Nebula - Kelling Heath Ha and DSLR

[Carole]

OK Fay thanks, also sorry Mark, not got around to doing it yet.
I'll do it tomorrow.

Carole

[Fay]

Processed with PS

[MarkS]

Here's my version using your lights, darks and flats:



I only used the DSLR data - not the H-alpha.  You don't need to ask what I used to do the processing but I'll tell you anyway:  Iris.

I didn't use your bias frames for 2 reasons:
1) They weren't well matched to the lights and so introduced extra banding noise
2) The flats were ISO 100 so using ISO 800 bias frames causes a mismatch - this might also be part of the cause of your banding.

So I used a synthetic flat: all pixels have value 1024 (the correct value for the Canon 450D).

Larger version here:
http://www.markshelley.co.uk/Astronomy/2012/carole_california.jpg

By the way, I noticed quite a few faint fuzzies in the background.

Mark

[Carole]

Thanks Fay, what did you stack it with?

Thank you Mark.  
That was interesting what you said about the Bias frames as I always thought that they had to be at the same ISO as the Light and darks, and have always been told that the correct way to do flats was AV 100 ISO.  It might certainly explain why there is a problem with the banding and flat calibration if in fact the Bias should also be done at the same ISO as the flats - 100 ISO.  

I have never had any success using an artificial flat as I can never get the subtract procedure to work properly in photoshop.

Mark I didn't put any Ha data into Dropbox, but I will if you want to have a "go" at it.

My problem now though is I need to spend time learning to image and process with the Atik, so learning what to do and what not to do with the DSLR is sort of "on the shelf" at the moment.

Thanks for processing the image both of you.

Carole

[Fay]

DSS Carole only DSLR subs, flats bias lights darks

[Mac]

I have never had any success using an artificial flat as I can never get the subtract procedure to work properly in photoshop

Probably because the subtract only works correctly in 8bit, there are a lot of issues with the 16bit functions, not doing as they should.

Mac.

[Carole]

Probably because the subtract only works correctly in 8bit, there are a lot of issues with the 16bit functions, not doing as they should.

Hmmm might give that a try, though it would be ideal to subtract the flat at the beginning of processing rather than the end, but to prove a point I might give it a "go".

What version of PS do you use Mac?  I have a good reason for asking but don't want to hi-jack my own thread so won't explain here.

Carole

[JohnP]

Blimey 11 reprocesses of the same image in one thread....! must be a record.....

btw - Robert's looks the best on my monitor..

[Mac]

What version of PS do you use Mac?

CS4 now

[Tony G]

Blimey 11 reprocesses of the same image in one thread....! must be a record.....

Well I'll never need to go there on holiday, as I seem to know it now like the back of my hand. Saved me a fortune! 

Tony G