Colour IC405

[swag72]

I took some Ha data of IC405 and this turned out OK. So last night as it was clear I decided to add some RGB star colour. This really is the first time I've really tried to do this with a nebula, and I found it rather difficult. Can you give me some pointers on what I could have done differently or better? I just can not see the wood for the trees anymore!

Details

M: HEQ5

T: Pentax 75SDHF

C: Atik 460EX mono with Baader RGB and 7nm Ha filters

12x300s each RGB and 17x1200s Ha

Bias frames only used.

[Shibby]

Hi Sara, although that looks very lovely indeed, perhaps you haven't stretched the RGB data enough... The stars look great but I can't see any of the expected blue reflection nebulosity.

[swag72]

Cheers Lewis for your comments. I really don't have enough RGB data for any mega stretching, so I couldn't get the blue reflection out, which is a shame, I agree. This was a first for me with this camera, so I'll forget this for now and move onto something else but gets loads more RGB!! THe moon was NOT my friend with this one!!

[opticalpath]

Hi Sara. I'm assuming you you did it as a Ha(L)RGB composite. How did you blend in the Ha with the RGB layer, and what did you use as a luminance layer?

If the processed Ha image is deep and contrasty compared to the RGB image, it can be tricky to use it straight off as a luminance layer, or to apply it directly into the red channel.

Adrian

[swag72]

I did use this as an HaRGB image. I'm sure that I've done stuff wrong, but firstly I added the Ha to the red channel and then I copied and pasted the same Ha data and added it as a luminance layer over the top of the RGB. The first time I addded it I used it at about 50% opacity, upped the saturation then added it again.

I know that the stars in the nebula are awful!!! This ran away with me really, I thnk as I had so little RGB data (1 hour each channel) and I only really was using it as a star layer. I certainly didn't stretch it to bring out the nebulosity detail - Perhaps that was wrong.

Processing ................... I hate it!!!!

[Mark72]

Send as your data Sara, we will take care of it;)

Nothing wrong about the image and stars. To get blue reflection out of it you need indeed more Blue and Luminance

Mark

[opticalpath]

I did use this as an HaRGB image. I'm sure that I've done stuff wrong, but firstly I added the Ha to the red channel and then I copied and pasted the same Ha data and added it as a luminance layer over the top of the RGB. The first time I addded it I used it at about 50% opacity, upped the saturation then added it again.

I know that the stars in the nebula are awful!!! This ran away with me really, I thnk as I had so little RGB data (1 hour each channel) and I only really was using it as a star layer. I certainly didn't stretch it to bring out the nebulosity detail - Perhaps that was wrong.

Processing ................... I hate it!!!!

You're being too hard on yourself, Sara! This is tricky and you got a good result.

Introducing the Ha/ Lum in stages (multiple luminance layering) was exactly the right thing to do - building a new strengthened intermediate RGB layer before recombining that with the luminance again at higher opacity. You could even try doing it in 3 or 4 stages, building up the lum. layer opacity more gradually starting at a lower opacity. If you had an ordinary (unfiltered) luminance image, it would be worth experimenting with a blend of unfiltered and Ha for luminance .... or create a pseudo lum. from the RGB or Red image and blend this with the Ha. Look at the RGB image in Lab mode; the luminance channel here is what you're starting with. Compare that to your proposed luminance layer for the LRGB composition (Ha or Ha/ unfiltered blend). If they're dramatically different, adjust the lum processing or blend to make them a little closer - at least for the first LRGB combine.

Try mixing Ha with RGB red channel using Image/ Apply Image (Lighten). This allows you to fine tune the way you intensify the red channel and to adjust the black point levels so you don't wash out the background. It often helps the colour to add some Ha to the blue channel too, at low opacity (Apply - Lighten - 10% say) to simulate the colour of the H-beta that is also present. I usually find that a more gently processed Ha image works better for blending into the red channel, so it's not such a dramatic change to the native red channel and to avoid clipping or maxing out the red channel. Certainly make sure that the Ha image you use for this has a max. brightness well below 255.

A good strong starting RGB image certainly makes life easier. Even when you know this, It's hard to avoid the temptation to go for broke on Ha and be a little stingy on RGB. Ask me how I know and when will I learn

Adrian