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36440Horsehead and flame nebula in Ha SII & OIII emission line colour

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  • Gordon Haynes
    Oct 31, 2008
      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 <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.

      Horsehead and lame nebula in emission line colour

      Thanks for looking, a full size high resolution version can be seen on

      Best wishes and more cold clear skies


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