Dave, I assume the spikes are from the aperture adjustment on the Micro Nikkor lens. I didn't really notice them on the first image taken with the lens, perhaps because there were no bright stars in the field, but the spikes are pretty obvious in this image. If anyone knows for certain, I would love to know. Cheers, Tyler _____________________________________________ -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Dunn, David Sent: Thursday, November 15, 2007 8:27 AM To: Utah Astronomy Subject: RE: [Utah-astronomy] New Comet Image - The tail is essentially gone I am curious, what causes the 18 spikes on the bright star? I really appreciate you sharing all of these pictures with us. You do a really nice job. Thanks. Dave -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Tyler Allred Sent: Thursday, November 15, 2007 7:42 AM To: utah-astronomy@mailman.xmission.com Subject: [Utah-astronomy] New Comet Image - The tail is essentially gone Hi all. I imaged comet Holmes on the night of the 12th and the result is posted on my website at the link shown below. http://71.18.228.62/images/Holmes%2011-12-07.jpg It appears that the ion tail is gone but the shape of the comet is interesting. Cheers, Tyler _____________________________________________ _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com

I agree it is a excellent picture. I just couldn't think of what would cause that many spikes. This makes perfect sense. Thanks. -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Rob Ratkowski Photography Sent: Thursday, November 15, 2007 6:30 PM To: Utah Astronomy Subject: RE: [Utah-astronomy] New Comet Image - The tail is essentially gone Tyler those are diffraction spikes off the aperture blades of lens. the number of spikes represent the number of blades in the lens. STILL a nice photo!! aloha Rob _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com