Pelican nebula 1st attempt at colour emission line imaging

[GordonH]

Hi all

After an abysmal May as far as weather is concerned I have finally got my filter wheel up and running and as the sky was clear last night (it was up till mn) I thought I'd chance my luck and have a go at the Pelican nebula. After I got everything aligned I was ready to begin just before 12mn but as the camera was taking its dark frame for auto dark subtraction patchy clouds started rolling in from the southwest and this was the pattern for much of the rest of the evening. I decided to stick with it though and managed to shoot 7x10 minute unguided each of Ha, OIII and SII (the last one of the OIII and SII had to be junked because daylight stopped play). The was a period of about an hour when there was no cloud at all but the rest of the time patchy clooud came very close to cygnus and on a few occasions covered where I was imaging (thankfully only for a few seconds each time)

I combined the 6x10 minute SII(red), 7x10 minute Ha (green) and 6x10 minute OIII (blue) Hubble palette style. Onle 3 small iterations of curves were used as well local area contrast in Noels tools. No levels were used. Considering the rush and the threatening cloud I am well chuffed. I have also enclosed a cropped close up of the Pelicans "neck" to show the chimneys a bit better.

Thanks for looking

Clear skies

Gordon

[steppenwolf]

I've commented elsewhere but its worth saying again - fascinating image!

[LostNSpace]

A very nice image Gordon, plenty of detail and colour.

Well done

Mark

[Paxo]

Wonderful image Gordon, but I can't but wonder about one thing. Why did you use the SII data for the red channel and Ha data for the green.

The respectiv wavelengths of these emission lines are:

Ha - 656.3 nm - Red

OIII - 495.9nm - Blue

SII - Has a doublet emission at 671.9 and 673.0 nm - Green

Steve..

[GordonH]

Hi Steve

In answer to your question there are two commonly used colour palettes used for emission line imaging, the one is as you quite rightly say Ha(red) OIII(blue) and SII(green), the other one is the hubble palette as used by that big expensive telescope up there which uses SII(red) Ha(green) and OIII(blue). Because our eyes see everything in "true colour" or RGB we always asign the correct filters to their respective channels, however we don't see in emission line wavelengths so the order in which the filters are asigned are partly to do with personal taste but it can also help highlight different detail.

Best wishes

Gordon

[Paxo]

Thanks for that Gordon, the technique certainly makes for some spectacular images.

Steve