1st LRGB - M3

[Deneb]

Hi

After muckin around with my recent phd problems, i managed to catch some new data of M3. Wanting really to understand how to combine LRGB together i've produced this image. Excuse the Ghastly Dust Bunnies in the image as I have to really look at how to take flats after each filter run. Taken with a SW80ED, Atik 314L+ @ 7x3mins L-R-G-B.

No Darks or Bias used.

Nadeem.

[stolenfeather]

Very nice image indeed Nadeem!

Isabelle

[AndyUK]

Nice one, Nadeem! Is that a full frame shot with the 80mm...?

[Deneb]

Yep, thats a full frame Andy.

Nadeem.

[AndyUK]

Wow... The 314 certainly gets in close, even with "only" an 80mm...! You've got roughly the same FOV here as an APS-C chip gets with the MN190 (but without the dreaded noise artefacts...). Can't wait to get my extension tube this week...

[dc509]

Nice one!

d

[ollypenrice]

Encouraging start Nadeem.

I don't think your colours are fully aligned in this one. Looking as closely as I can I would say red was lower left of Luminance and blue upper left slightly. I sometimes get this and realign them by hand in AstroArt. (Only the stacks, not each frame!) In auto align programmes the result is often good but go into the corners and give it a merciless glare at high magnification because small errors get past the auto systems on occasion and you don't see the trouble till you have wasted two hours in Photoshop....

Olly

[Deneb]

Your right Olly, there is some mis-alignment, I saw this when I converged the channels together, It was pretty bad when you do a Auto Align in CCD Stack, but if when I chose to do a manual star selection for alignment, the results were better but not perfect. Im having some problem working out when the LRGB channels are merged & ccd stack asks you do you wish to correct the background ? If you apply - the colours channels shift to the right, then the blue & red channel are more apparent.

Nadeem.

[ollypenrice]

What I would do is avoid merging the L channel at this early stage. Save it for later because the RGB processing is different. What I want in RGB is good alignment, good saturation and low noise. In L I want strong contrast, sharp detail, deep stretch of the faint stuff and no burning out of the bright. So I process L and RGB accordingly.

Then, after co-registering the L to the RGB (I have Registar so I use it because it is infallible) I may try applying the L in various ways. The most obvious is as a layer in blend mode luminosity. That way you don't have to apply it at a 100 percent if your colour is not strong enough. Or you can adjust the RGB in Curves and Saturation to get it to work in harmony with the L.

Usually problems in aligning arise from camera rotation in interrupted runs or polar alignment. That is very common.

Olly

[Deneb]

Hi

A few days ago, i reprocessed this image. Now this timearound I have just processed the RGB. I can say the L channel was out of alignment, i think that was causing the colour shift.. apart from a lack of saturated colour - i think it's a better result.

cheers

Nadeem.

[ollypenrice]

Miles better! Now you have the colour layer done could you not align the Lum to the RGB?

Olly