Suggestions for going forward with this image

[andrewluck]

This is a crop of M81 & 82 from a wider field. I'm stuck going forward with this image trying to perform an HDRMultiscaleTransform. What makes M82 look better (smaller image scales) has a horrible impact on M81.

Am I using the right tool here or should I be looking for an alternative approach?

Original data here: http://ubuntuone.com/3MPqNfXqZ7PLcdIKJ7B6Tp

Andrew

[sreilly]

Andrew,

It might help to explain what you have already done to this image as well as posting the original combined image prior to any processing.

-Steve

[andrewluck]

Hi Steve

That's quite easy as I haven't got very far with this one at all.

DBE, Masked stretch, TGVDenoise.

Original stack is here: http://ubuntuone.com/5VA5WezW8JnwO307hwLSmN

Cheers
Andrew

[Harry page]

Hi

Well I had this problem as the galaxy's respond differently to HDR wavelets ( as you said)

So I slightly cheated I cut the image in two ( leaving a overlap) did the old HDR on each galaxy and then recombined them using the gradient mosaic tool

I am sure the very correct answer is to create a mask , but sometimes I need a simple way 

Harry

[andrewluck]

Hi Harry

A crafty solution, nice one. I'll give it a try.

Cheers
Andrew

[sreilly]

Far better an answer than I was able to do. The brightness differences in the two galaxies are a bit much to handle as one image. I was able to come up with some ideas but they related back to my PS days using layers. Harry saves the day again.

Steve

[Juan Conejero]

What makes M82 look better (smaller image scales) has a horrible impact on M81.
Am I using the right tool here or should I be looking for an alternative approach?

In my opinion, you have two options:

* Try to reach an equilibrium point to show both objects on the same image, processed as a unit. This means that neither M81 nor M82 will be shown in optimal conditions (for some definition of "optimal"), but the image as a whole will be optimal.

* Create two subimages, one of M81 and the other for M82, and process them separately. Once processed this way, the images will be incompatible in terms of information representation.

Other options, such as masking one of the objects or a divide-process-merge strategy, are unacceptable in my opinion. In general, when different objects in the same image are processed separately by applying arbitrary selection criteria, the result is not a valid astrophotograph. The reasons are the same that are applicable when somebody paints a mask by hand to sharpen here and there because it looks better that way. The keyword here is paint.

[sreilly]

* Create two subimages, one of M81 and the other for M82, and process them separately. Once processed this way, the images will be incompatible in terms of information representation.

Other options, such as masking one of the objects or a divide-process-merge strategy, are unacceptable in my opinion. In general, when different objects in the same image are processed separately by applying arbitrary selection criteria, the result is not a valid astrophotograph. The reasons are the same that are applicable when somebody paints a mask by hand to sharpen here and there because it looks better that way. The keyword here is paint.

Wouldn't that then be true of any mosaic? Or am I looking at this wrong. Aren't mosaics several processed images combine to make a larger field or are they first combined and then processed?
I've never done one so I'm uneducated on this.

Steve

[Juan Conejero]

Hi Steve,

A mosaic, when correctly built, is a single, coherent image. With PixInsight's mosaic construction tools (if properly used) you get an unprocessed, linear image. The result is the same as if the same field had been acquired as a single image.

[Harry page]

Hi

While most of the time I will abide by the great "sage" Juan , in this case My opinion differs

My divorce and remarry option is not painting and respects the data within the image 

ultimately We could argue that any sort of mask is wrong  8)

But as most things in life " the choice is yours"

Regards

Harry Page