Thanks Jerry, That pattern is clear in every subexposure, and I have no idea what causes it. In my RGB images, the colors alternate along the length of the diffraction spikes. It is a little wierd. Does anyone have an explanation for this effect? Cheers, Tyler Sent from my Verizon Wireless BlackBerry -----Original Message----- From: "Jerry Foote" <jfoote@scopecraft.com> Date: Tue, 7 Jul 2009 21:36:36 To: <utah-astronomy@mailman.xmission.com> Subject: Re: [Utah-astronomy] An image for you purists out there - Pelican Hi Tyler, That is a very fun image. Scanning through the detail really blows your mind. I do have a question: In many of your images the diffraction spikes around the bright stars show a "dotted" pattern. What is causing this? With the LRGB images I had always assumed that it was part of the combining of the LRGB images but this one is H-alpha. Looking closer I wonder if it isn't a moiré pattern of the multiple images coupled with a small dither between images. Again very nice. Jerry Foote ScopeCraft, Inc. 4175 E. Red Cliffs Dr. Kanab, UT 84741 435-899-1255 jfoote@scopecraft.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://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com