ClarkVision Photography: Astrophoto 1 Gallery

Home   Galleries   Articles   Reviews   Best Gear   New   About   Contact   Gallery Index   Previous   Next
image comet.holmes.c10.31.2007.36s2.d-c800.jpg is Copyrighted by Roger N. Clark, www.clarkvision.com

Comet 17P Holmes on Halloween

Periodic comet Holmes underwent a 17-million fold increase in brightness in mid-October. It rapidly became visible to the unaided eye in light polluted cities. The cream color is due to dust, and the hints of green are due to carbon and cyanide.

Technical. Canon 1D Mark II digital camera with 500 mm f/4 L IS lens at f/4. The image is the sum of 36 one-second exposures at ISO 1600 from a stationary tripod. The short exposures were necessary to prevent trailing of star images due to the Earth's rotation. Dark frame images were subtracted, the images aligned, and averaged using sigma clipped average in ImagesPlus. The image was then stretched in ImagesPlus using digital development and touched up with curves in Photoshop.

The Exposure Factors, CEF, CEFA are measures of the relative amounts of light received from a subject. It can be used to fairly compare wildly different lens/telescope apertures and exposure times. For this image:

Plate scale is 3.4 arc-seconds/pixel in the original, and 4.8 arc-seconds per pixel in this cropped and slightly reduced image.

Please visit my Extensive Articles on Photography .


Keywords to this image = astrophoto-1 comet digital_astro

Image ID: comet.holmes.c10.31.2007.36s2.d-c800.jpg

All images, text and data on this site are copyrighted.
They may not be used except by written permission from Roger N. Clark.
All rights reserved.

Home Galleries Articles Reviews Best Gear Science New About Contact

Obtaining Images or Prints

Last updated March 10, 2024