Debayer and alignment sequence

[DB]

Hello

I am using images from an SBIG one shot color camera, outputting .fits files. When I perform debayer, imageintegration, DBE, and finally histogram stretch I get a different result to when I add staralignment: debayer, staralignment, imageintegration, DBE, and finally histogram stretch. 

If I look in histogramtransformation at an individual file that has gone through staralignment, the individual RGB traces are slightly shifted relative to each other and particularly the height of the histogram is attenuated. 

Any advice welcome!

thanks

DB.

[pfile]

surely though the result of the debayer, imageintegration, DBE flow is messed up? even if you are not dithering the stars are not going to be in exactly the same place in each image due to polar alignment error or differential flexure. or are these extremely wide-field images?

simply put, staralignment is a necessary part of the flow, so omitting it does not make sense and comparing to an integration made with non-aligned subs does not mean that much. if the images are really wide-field then perhaps they appear to stack OK without alignment but it should still be done in that case.

i'm not super surprised that the histogram of an image that went thru SA is a little different than an image that did not, because SA necessarily interpolates pixels and may "smooth" it out a little bit as neighboring pixels are combined in the interpolation.

rob

[DB]

Rob

Thanks for the fast response.  It is an image of M83 shot on an ST-2000XCM, so not super wide field. 

I am getting back to PI after a long absence and am relearning on some images I captured several years ago.  Surprisingly the stars are a little irregular but not very much so without star alignment, so I hadn't noticed it as a missing step.

I recall that star alignment and image integration follow debayer.  Is there anything else I need to know about the sequence of stpes or can you point me to a video? 

In the final processed images it would be good to smooth the pixelated stars a little and deal with bloated stars.  I have watched Richard Bloch's video on deconvolution.

thanks again.

David

[pfile]

i guess with good polar alignment and a small # of subs it's possible that the frames already overlap one another for the most part, but SA is capable of sub-pixel accuracy. at any rate it's a step that you'd almost never omit for any reason.

i think you have the flow down properly - calibrate, debayer, register, integrate, process.

there are a load of videos and tutorials here: http://pixinsight.com.ar/en/

also adam block just started making (for-pay) PI videos; also of course warren keller has his (for-pay) video series and book as well.

rob