It was precisely this phenomenon that allowed a Celestron Ultima 2000 belonging to Don Colton to split Eta Cor Bor (.8 arc second) where the 9" Clark could not. Both were being used at somewhere around 450x. -----Original Message----- From: Chuck Hards [mailto:chuckhards@yahoo.com] Sent: Thursday, February 27, 2003 8:51 AM To: utah-astronomy@mailman.xmission.com Subject: Re: [Utah-astronomy] Goodwin Mask (long) Because diffraction can be "channeled", sometimes telescopes with large central obstructions or widened spider vanes prove useful, especially if splitting close double stars. By moving energy from the central spot into the diffraction rings, the spot can be decreased in size and allow close companions to be seen, where in an unobstructed system, while the rings are weaker, the central spot is larger and overlaps the companion star. C. __________________________________________________ Do you Yahoo!? Yahoo! Tax Center - forms, calculators, tips, more http://taxes.yahoo.com/ _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy