HaRGB combination problems?

[E_ri_k]

Hi, I must be doing something not quite right…..I'm trying to create a HaRGB image in PixInsight. Have a look at the image! What is going on with the stars!?

My approach is basically, Align, crop, DBE, ColourCalibration, and Combine, using the Ha as Luminance. On their own the colour data looks normal, and the Ha is fine, but together it's weird? Haven't done any fine processing yet, just trying to get the colour thing sorted.

Any ideas:confused2:
Erik

[RickS]

G'day Erik,

You'll need to match the intensity of the Ha with the RGB data if they are all linear (sounds like it from your description).

Try this:

combine R, G & B
extract Luminance from the RGB image
apply LinearFit to your Ha data with the Lum as the reference
combine your modified Ha data with the RGB


Cheers,
Rick.

[E_ri_k]

Cheers Rick, yes alt he data is linear. Had a quick go at what you suggested, still not right. I'll have another crack in the morning. Maybe I'm too tired and missing something haha!

Erik

[RickS]

I would expect to see some coloured halos around the stars because the Ha stars will be smaller than the RGB stars but it shouldn't look like that... I'm happy to take a look at the data (maybe just a small crop of each master) if you get stuck.

Cheers,
Rick.

[E_ri_k]

Yeah, strange... If you would that would be great, I'd really appreciate it :) I'll upload some crops to Dropbox in the morning if you like.
Erik

[RickS]

Erik,

Here's a quick process of the Dropbox data. My usual processing regime is to deal with L and RGB separately and then combine them late in the process well after stretching. Trying to combine the linear data gives a result like you posted. I think it's because the Ha needs a much bigger stretch than the RGB.

Here's what I did:
- StarAlignment to register RGB masters with Ha
- Crop
- Combine R, G & B with LRGBCombine
- Stretch RGB aligning histogram peaks for a rough colour calibration
- Stretch Ha
- Combine Ha and RGB with LRGBCombine

I wasn't entirely happy with the look of this, so I:
- extracted the Lum component of the RGB image
- used PixelMath to blend the Ha and Lum in 2:1 ratio
- Combined the blended Lum and RGB with LRGBCombine (tweaked the Lightness slider a little for best result)

Hope that helps.

Cheers,
Rick.

[LewisM]

I still prefer using the Gendler or the Starizona techniques in Photoshop to combine H-a to the otherwise completed LRGB set.

I am antiquated I know, but PI gives me the willies still.

[RickS]

Some people grok PI quickly and others don't. It requires a mode of thinking that seems to suit some people more than others. Of course, there are people that find Photoshop difficult too but that's tough luck - there aren't many other options for general purpose image processing.

Cheers,
Rick.

[E_ri_k]

Thanks Rick, you are a legend :) I had another play with the data, and it's looking promising….Hopefully I'll update my other thread with a completed version……….

Erik

[LewisM]

You should write a quick PI how to Rick. You Carina image is lovely!Just a few step by steps with ratios, figures etc. Really appreciate it if you can one day!

I keep trying PI (paid for the license, so I force myself!), and KNOW it will improve my [poor] imaging processing, but I get confused by some of it, and always revert to throwing it in MaxIM and PS.

[RickS]

Thanks, Lewis.

I posted a LRGB workflow summary here: http://www.iceinspace.com.au/forum/showthread.php?t=117544

There are some decent IP4AP video tutorials and I believe that Ron Wodaski is writing a book.

Cheers,
Rick.