AnnMarie's Blog

Now that 17P/Holmes is developing something of a tail, I’ve been keen to get a deeper image than that of a few nights ago (that showed the core & initial coma only). Whilst having our Guy Faulkes night bonfire, the skies cleared out. So after some family comet viewing through the C6, I changed for my 400mm Canon lens & started imaging. The skies clouded over again at about 1am 06/11/07 UST, by then I had captured almost 4 hours of exposures, here’s the image …

  Click image for larger view …

This image shows the Comet, from the core, right through its layers of coma and out to the tail, which is now developing beautifully. The image uses different length exposures to capture details with vastly different luminosity, as detailed below:

 8 x 30s           240
 1 x 90s             90
15 x 121s     1815
75 x 151s   11325
 3 x 242s         726

This gives a total integration time of 3 hours 56 minutes & 36 seconds. Software used to stack & process the subs, included: Iris, PixInsight, Image Analyzer, Photoshop & Lightroom. Different processings of the data were undertaken and these were amalgamated via layering in Photoshop. Initial processing in Iris included correction with 10 flats, 5 flat darks & 15 darks; the corrected & stacked images were binned 2×2 in Iris before output to PixInsight.

On a note of scale, the diameter of this comet’s coma is now reported to exceed that of the Moon’s orbit around the Earth. In contrast, the actual solid comet core is only a little over 3 kilometers across.