NGC6888 - "An unusual Crescent!"

[GordonH]

Hi

I had previously taken some Ha and OIII data on this and managed to get out and get 3 hours of SII data in 30 minute sub frames. Normally I process my narrow band images using the HST palette partly because I prefer it but also because it is more scientifically correct in that the filters are asigned in order of wavelength, but I found that using this palette the OIII envelope that surrounds the main nebula didn't show up very well so I changed to a palette commonly used by the Canada France Hawaii Telescope (CFHT) where the filters are asigned to RGB in the order of Ha:OIII:SII.

This was taken with my current set up of Takahashi FSQ106ED at f5, Paramount ME and Starlight Xpress SXVF H9 with exposures of 7x30 minutes for Ha, 8x30 minutes for OIII and 6x30 minutes for SII, I would have got more SII but clouds interrupted the session. The master frames were colour combined in Maxim DL with a weighting of 1:2:7 for Ha:OIII:SII and processed in Photoshop CS2 using levels and a series of 'S' shaped contrast curves, in order to better distinguish between the main nebula and OIII envelope I used selected colour to shift the colour balance.

All three versions (Ha, Ha/OIII and CFHT palette) can be seen on the Nebulae 2 page of the image gallery of my website

Imaging The Heavens - Home Page

and there is a full size image at the following link

NGC6888 - Crescent Nebula in CFHT palette photo - Gordon Haynes photos at pbase.com

Thanks for looking

Best wishes and clear skies

Gordon

[sgazer]

stunning image. A lot of time and complex processing has gone into that one.

[ollypenrice]

Greetings, Gordon. An excellent choice of palette for this one. It is often very hard to see what is going on in the O111 channel but this is very coherent and clear.

An informative and attractive image.

Olly

[Espi]

Great image, thanks for sharing.

[fatwoul]

This image really makes clear the point of CFHT and HST palette images, at least as far as making it easier to distinguish the regions of different substances in an object. What it also makes clear to me is how much longer a CCD has to soak in order to bring out all the detail "behind" the Crescent.

[AndyUK]

I have to admit, I hadn't heard of CFHT pallette before...

I'd seen images of the crescent in HST and decided that (for me) it looked better on the eye as an HOO image, but having seen this version I think I'll see if I can revisit it and try this pallette myself - It looks more like a gold nugget!