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Horsehead and flame nebula in Ha SII & OIII emission line colour

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Hi all

Following my posting of the Universe Today article where my Ha image of the Horsehead and flame nebula was featured I thought I would have a go and add the other two emission line filters (OIII and SII) to see what results I would get. It was a very clear night on Tuesday and after doing some imaging earlier in the evening I was ready at about 1.30am to tackle this subject as it had just appeared around the corner of my house. I took 12x10 minute unguided subframes for OIII just in time to do a meridian flip and then 12x10 minutes unguided for SII. I processed these together with the 12 best subframes from the Ha data taken last week. While adjusting the settings in Maxim DL when colour combining I found that using Ha for luminance at 100% and the same Ha data for Red, SII for Green and OIII for Blue with a repective weighting of 2:3:2 for the three channels gave the most pleasing colour blance to my eyes on my monitor (this is probably not he most conventional palette to use but with emission line imaging this doesn't really matter). I saved the result to 16 bit TIFF and then processed in Photoshop CS2. I was quite surprised at the end result because I think I have managed to get the intricate detail that is associated with emission line imaging but at the same time retaining the more subtle colour hues associated with traditional RGB imaging. Only dark subtraction was used using 10x10 minute dark frames median combined that I took earlier in the summer. No flats or autoguiding were used.

Compare this image with the Ha version on my website http://www.imagingtheheavens.co.uk

As a footnote it was freezing cold, the roads were iced over when I finished and the cars frosted over, the dew heaters did their job perfectly as did my latest purchase, a "Mountain Equipment" down jacket, I was sat outside in the shed virtually all night apart from making the occasional hot drink and I was as warm as toast.

Thanks for looking, a full size high resolution version can be seen on http://www.pbase.com/imaging_the_heavens

Best wishes and more cold clear skies

Gordon

B33HaSIIOIII.jpg

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G'day Gordon,

Very good work mate. Are you going to mix some Ha into that? Would love to see all three narrow band channels of that.

Ray

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G'day Gordon,

Very good work mate. Are you going to mix some Ha into that? Would love to see all three narrow band channels of that.

Ray

Hi Ray

Thanks for the comments, I think you missed part of my description regarding the Ha data, the LRGB ratios are as follows

L=12x10 minutes Ha

R=12x10 minutes Ha

G=12x10 minutes SII

B=12x10 minutes OIII

I used 100% for the luminance channel and a weighting of 2:3:2 for the respective RGB channels so as you can see there is plenty of Ha data in the image, perhaps what is surprising is that the end result looks more like a traditional RGB image than an emission line image. This has more to do with the combination that I combined the channels and also the weighting I used

Best wishes

Gordon

:smile:

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Hi All

Here is a slightly tweaked, brighter, more vivid and colourful version, this was done with minor adjustments to the curves only

B33repro.jpg

Thanks for looking

Gordon

:smile:

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