I've never had difficulty with Rigel with an "unmasked" 10-inch f5 Newt. If I can't make out the companion, I wait an hour for the position to change and to see if it was lost in the glare of one of the diffraction spikes from the secondary, or I try rotating the tube assembly. Even with bright diffraction spikes, Rigel's companion hasn't been difficult for me. Not so for other pairs I've tried observing that way. I believe that the same principle behind the "apodizing" mask makes observing close doubles easier with a SCT than with a quality refractor of comparable aperture. This was apparent one night in May 2001 while observing Eta Cor Bor with both Don Colton's Ultima 2000 (Celestron 8-inch SCT) and Siegfried's 9-inch Clark. The large central obstruction of the SCT in effect made the Airy disk proportionately smaller than that in the Clark and allowed the pair (0.8 arcsec, as I recall) to be split easily. At the same time, I couldn't split the pair in the Clark, nor I believe could anyone else. (I was so impressed by the performance of the Ultama 2000 that two weeks later I bought one myself. Siegfried wouldn't part with the Clark for the same price, although I offered...) -----Original Message----- From: UTAHDEB@aol.com [mailto:UTAHDEB@aol.com] Sent: Monday, October 13, 2003 1:14 PM To: utah-astronomy@mailman.xmission.com Subject: Re: [Utah-astronomy] Fwd: Rigel and companion Joe, According to the Astro-League's Double Star list, the separation is 9.5 arc seconds and the PA is 202 degrees. The primary star is 0.1 mag and the secondary star is 6.8 magnitude. Rigel was my first observed double when I bought my 4 inch refractor back in 2001. I'll try to take a picture of Rigel this winter with my digital camera. I don't know if more vanes could help. Debbie _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy