How to create a colour image from Mono cam?

[blinky]

Last night was the first time I have used the Orion Deep Space cam with the newt. I love the image scale but I am just not sure that greyscale 'floats my boat' so to speak! I dont want to go down the RGB filter route but I do have an OIII and Ha filter. I believe I can capture some of that data and add it in along with the grey and also use one of Noels tools to synth the blue channel. How do I do this and do I then use the greyscale data as the Lum channel? The weather this morning is looking OK so I may get a chance to capture this tonight.......

[roundycat]

many targets do not radiate much in the way of Ha and even fewer Olll so make sure you pick a target that is 'bright' in both or you will be disappointed. Either way you will likely need much longer exposures than you have been using.

Usual practice is to use Ha or Sll for red and Olll for blue. If you use Ha for R and Olll for B then you need to get your processed channel masters into Photoshop and add together the two by dragging one into the other as a new layer. Hold down the Shift key as you release the mouse and it will automatically align if the layers are the same size/ orientation. (You should align the images properly before taking them into PS) Set the top layer to 50% opacity and flatten image. You now have synthetic Green. Save all three and put all three together in PS by using Channel Merge.

You will need to fiddle with relative channel strengths (channel mixer) to get your ideal overall colour. If you want to use luminance data as well add it as a layer to the finished RGB and set layer blend to colour or luminosity.

Dennis

[blinky]

I should have said the target will be M101. Do you think I will get much in the way of Ha/OIII from that target? From the mono version i think there may be some Ha regions but am not 100% sure.

[Ben Ritchie]

You'll get almost no OIII (other than the broadband emission from integrated starlight that happens to fall in the OIII band). So that will effectively act to block 99% of the light from the galaxy.

There will be some H-alpha from star-forming regions, but on its own it's not a very efficient way to image the galaxy - basically for galaxies H-alpha is a good thing to add in to 'traditional' LRGB data, especially for face-on spirals like M101 which will show a lot of star formation in the disk, but it's still dropping a lot of starlight.

[roundycat]

when I said pick an object that is bright in Ha and Olll I should have said no galaxies. They are best left to RGB with or without added L.

NGC7000 is starting to come up in the East now together with IC 5070 and IC 1318, all in Cygnus. Also the Veil western end, NGC 6992. All of these go well in narrowband but you may not like the colour.

Dennis