Ok, here is an odd question

[Zathris]

Ok, here is an odd question. I have a Astronomics 13nm Ha filter and a Lumicon OIII filter. I have been waiting for a SII filter to try some false color narrow band imaging, but had a thought. If I wanted to do a tri-color image of Ha, OIII, and Hb of say the horse head or the California nebula could I do this? Take a Ha image, an OIII image and an image using a UHC filter. Then use the OIII image to combine with the UHC image using the difference blending method to get just the Hb data from the UHC image. Then make a Ha, OIII and Hb from that data?

Zathris….

[budguinn]

Z, you can make a fairly good looking RGB image by just using HA and OIII. Steve Cannistra has a method that I've tried that works quite well

http://www.starrywonders.com/

....also Noel Carboni's AstroTools has an action that does this and works very well.

http://actions.home.att.net/Astronomy_Tools.html

bud

[Zathris]

I have read Steve Cannistra’s Ha and OIII method and realize it’s possible to use two data channels to get a tri-color RGB image. I guess my real question is weather it would be possible to pull the Hb data out of the UHC filter by removing the OIII component. My guess is that the data can be separated but I have yet to try.

Zathris….

[neilfleming]

Sounds possible, Zathris. Yes, you could subtract out the OIII from the UHC, but I believe the UHC has a pretty big bandpass.

Another alternative is to use Ha as red, OIII as green, and OIII plus 20% of Ha (to represent Hb) as the blue.

...Neil