Amazing Sky by Alan Dyer

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Comet Holmes 17P (4in Nov 1, 2007).jpg

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Comet Holmes, 17P, taken November 1, 2007 on an excellent night, in a telescopic close-up using a blend of exposures to record the range of brightness in the coma of the comet. The coma shows an extended cyan glow from diatomic carbon. This comet underwent a major outburst at this return and became large and bright enough to see with the unaided eye.

The fuzzy "nucleus" of the comet is the dot at upper left of inner coma; the other star in inner coma at right is a field star. The faint blue streamers at lower righty are from the wide ion tail. North is up, so the tail is to the S and SW.

The field of view is roughly 2.5º by 1.5º.

Technical:
Taken with the A&M 105mm apo refractor at f/5 with Borg 0.85x compressor/field flattener on Sky-Watcher HEQ5 mount. With the Canon 20Da camera at ISO400. Composite of 4 min, 2min, 1min, 30sec, 15sec, and 7 sec exposures, each exposure being a stack of 3 to 4 identical exposures. Registered and stacked in Photoshop (HDR mode did not produce usable result, so manually composited with sucessively smaller masks to reveal short exposure content around nucleus. Reprocessed in 2025.
Copyright
© 2007 Alan Dyer
Image Size
3480x2300 / 4.3MB
Contained in galleries
Comets
Comet Holmes, 17P, taken November 1, 2007 on an excellent night, in a telescopic close-up using a blend of exposures to record the range of brightness in the coma of the comet. The coma shows an extended cyan glow from diatomic carbon. This comet underwent a major outburst at this return and became large and bright enough to see with the unaided eye. <br /> <br /> The fuzzy "nucleus" of the comet is the dot at upper left of inner coma; the other star in inner coma at right is a field star. The faint blue streamers at lower righty are from the wide ion tail. North is up, so the tail is to the S and SW. <br /> <br /> The field of view is roughly 2.5º by 1.5º. <br /> <br /> Technical:<br /> Taken with the A&M 105mm apo refractor at f/5 with Borg 0.85x compressor/field flattener on Sky-Watcher HEQ5 mount. With the Canon 20Da camera at ISO400. Composite of 4 min, 2min, 1min, 30sec, 15sec, and 7 sec exposures, each exposure being a stack of 3 to 4 identical exposures. Registered and stacked in Photoshop (HDR mode did not produce usable result, so manually composited with sucessively smaller masks to reveal short exposure content around nucleus. Reprocessed in 2025.