Processing Ha in Galaxies?

[Russ.Carpenter]

These days I’ve been concentrating on galaxies. From time to time, I have separate files for Ha. My question is, what is the best method in StarTools for bringing out the concentrated knots of Ha in galaxies? I’m aware of these two postings by Ivo on combining Ha with RGB, but I’m wondering if there are any refinements for small but intense areas of Ha in galaxies?

http://forum.startools.org/viewtopic.php?f=7&t=236

http://forum.startools.org/viewtopic.ph ... 2532#p2532

Thanks for your help!

[Russ.Carpenter]

This is a follow up to my question about processing Ha data in galaxies.

My question was stimulated by something Ivo said a while back: "There are a number of ways to incorporate the Ha data into your processing. Which is just as well, as much depends on the object (ex. galaxy with just a few HII areas/knots vs a Ha-rich nebula as is the case here)." Ivo's recommendations related to processing an Ha-rich nebula, and not to a galaxy. To the best of my knowledge, Ivo has never given advice about Ha in galaxies.

I know that there have been discussions of processing Ha data in galaxies in other processing environments. For example, see this interesting dialogue relating to Photoshop: http://stargazerslounge.com/topic/23479 ... rgb-image/

I would appreciate any thoughts you might have. Thanks!

[admin]

Hi Russ,

Sorry - your post seemed to have slipped through the cracks...

The trouble with this subject is that it is highly subjective - even more so than a discussion about 'correct' visual colouring. Trying to merge a - for all intents and purposes invisible - narrow spectrum line with the broad visual spectrum is going to entail some choices that will be quite arbitrary. My personal favourite method is to add the Ha to luminance and rely on ST's Color Constancy feature, so that it does not impact colouring in the visual spectrum (only visibility of detail), yet others actually want Ha to impact colour (e.e.g accentuate the red in some gas knots). Either methods are valid, but both are, at the end of the day, hacks to visualise detail that otherwise exists outside the visual spectrum.

[Russ.Carpenter]

Hi Ivo,

Thanks very much for your thought-provoking reply. My impression is that the current trend in processing galaxies is to make them look like Christmas trees. Your approach has caused me to rethink that approach.

Here is my latest attempt at NGC 1531, which uses a separate luminance comprising Red, Blue and Ha. (The data base for the Gemini telescope does not include a green file.) I used the "color extract foreground" approach you recommended on 12/8/14.

In my opinion, StarTools has produced a wonderful image, which competes very well with the professionally processed images previously published on the Internet. I'm not entirely sure that it's worth the trouble to collect and use an Ha file when using your "color constancy" philosophy with a galaxy, but I need more experience to come to a conclusion.

Thanks again. Russ

ST Layers Final.jpg (347.79 KiB) Viewed 4718 times