What's the best way of combining a colour CCD image and an OIII image?

[Gem]

Hi all,

I was looking for opinions on the easiest way to combine images with a colour CCD camera and a filtered image (Ha or OIII) with the same colour CCD camera. In terms of software, at present I have AstroArt.

Any thoughts? :question:

[Bart]

Pixel math would be the way to go.

If using Photoshop then you would do a blend using layers and blending modes, opacity etc.

[gregbradley]

Open your colour image.
Create a new layer - call it Ha red
Copy and paste your Ha into that layer.
Change the blending mode to Lighten
Delete the Green and blue channels (click on channels, shift and click green then shift click blue, control A, delete). Click on rgb again and it should now show that layer as red.

Do the same for Ha as Blue but delete red and green channels. Set to lighten mode. Opacity to suit but usually between 10 and 20%, you are adding the slight blue from H Beta which is included in your Ha data.

You can use curves to accentuate or reduce the layer. Lighten mode only allows through those pixels which are lighter than the orginal image. So boosting or reducing curves makes it appear or disappear. Best method I have found.

Do the same for O111 but O111 is usually assigned to blue and green channels as above.

There is also bicolour which is combining Ha and O111 as red and blue and then creating a green channel of (Ha + O111)/2
I am not 100% on that formula that may be 2*(Ha + O111)/2.

Greg

[Gem]

Sorry - In what program? Photoshop? I don't have Photoshop, but if I need it - then I will get it.

[Gem]

Greg, is the method you explained used for a colour image with a filtered image? For example, I have a colour ATIK 320E. If I take a couple of hours of normal colour images and a couple of hours of Ha using the same camera - would I combine them in that way?
Forgive my ignorance, I am trying to get my head around it (visual astronomer at heart!).

[gregbradley]

Yes basically in Photoshop. I can do colour combines in CCDstack but they are usually just a starting point and then I export it into Photoshop.

There is a nice tutorial on how to process narrowband images at Astrodon.com. Its for use in Photoshop.

Atik 320E - is that a one shot colour camera? Yes combine the colour (either separate filtered colour or one shot colour) with Ha that way in Photoshop.

Greg.

[Gem]

Thanks!