I don't know all the reasons for doing the off-axis but that is what I have done with my previous filters. I do know that the Sun is too bright and just like you would mask your telescope down to get a better view of Mars, masking it down to 4" will help with keeping the light from washing out the detail when viewing the Sun. I am planning to buy 1/2 meter of the Baader solar film and cut it into 4.92" squares. I plan to sell them for about $4. That will handle the cost of the film and some poster board to protect the sheets. Thanks, David Dunn -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Kim Sent: Tuesday, March 06, 2012 10:50 AM To: 'Utah Astronomy' Subject: [Utah-astronomy] solar filter Anyone have thoughts about advantages/disadvantages of using a full-aperture filter versus an off-axis filter on a SCT? I'm trying to decide whether to purchase or make a full-aperture filter. If I purchase a sheet of film and make an off-axis filter I'll have enough film left over for one or two pairs of binoculars. I'm always for saving a buck or two - or 25 or 30 (for another piece of film). Kim _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Send messages to the list to Utah-Astronomy@mailman.xmission.com The Utah-Astronomy mailing list is not affiliated with any astronomy club. To unsubscribe go to: http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Then enter your email address in the space provided and click on "Unsubscribe or edit options".