Colour Image From H-alpha and OIII data ?

[jcm]

I'm thinking of taking some H-alpha and OIII images of the flame neb. ( cut through the moonlight?)

How would you get a colour image from these images - seen it done in some mags. but no explanation of how they did it.

John

[Kaptain Klevtsov]

The easy way is to open both greyscale images in photoshop. Copy one (either one) and call it green. Copy the other one on top as a layer of the green image. Set the opacity of the top layer to 50% and flatten the image. Now you have three greyscale images open.

In the channels menu, look for a little arrow pointing right at the top of the "pages" where the layer, channel and paths tabs are. Click on that and select combine images. Change the multichannel to RGB, choose which colour is which and you've cracked it.

HTH

Kaptain Klevtsov

[jcm]

OK , KK - thanks for the info. Will probably have a go at this tonight - subject to the haze clearing at about 2.30am

John

[Milamber]

I would add to the above ... use the Ha for green since Ha will usually give a crisper and better image than OIII and in the real world the green channel will carry more data. I know red is more the Ha area but trust me...

Arthur

[Kaptain Klevtsov]

I'll give that a go Arthur, makes sense after all what with DSLRs having 50% green sensors. You learn something every day here.

Kaptain klevtsov

[MartinB]

I think the reason Hubble chose the colours they did was to match the wavelength order of the narrow band with the full visual spectrum. SII has the longest wave length followed by Ha then OIII hence the allocation of SII - red, Ha - green and OIII - blue.

Another way to do this is to process your Ha and OIII images then do a sum combine using whatever align and stack software you use. Make this your luminence. Keep the Ha red. Duplicate the OIII and make one green and the other blue. Combine using the channels as described by KK. Since OIII is greeny blue this will actually give you quite a natural colour. Of course you could go the hubble route and see what that gives you. Great fun playing around!

If you want to go for something a bit more sophisticated have a look here http://www.starrywonders.com/bicolortechniquenew.html I'm planning to give this a whirl sometime soon.

[barkis]

Would you find this kind of information available in Wodaski's CCD Imaging book, or am I going to have to resurrect this post at some future date.

Ron.

[jcm]

Thanks for all the advice.

I am not sure which one to start with now

First thing I need to do is get some decent data and not let the camera/filter wheel move during the exposures.

See example below ( left it full frame so you could see the movement - could have cropped-did not bother with much colur adjustment)

John

[jcm]

If you want to go for something a bit more sophisticated have a look here http://www.starrywonders.com/bicolortechniquenew.html I'm planning to give this a whirl sometime soon.

Thanks for the link , Martin. I just about follow the the proceedure , going to have a go at it when I get the next set of H-alpha and O111 data.

John