I also have an off-axis mask for my 16" f5.5 dob. Chuck and Brent have given good technical explanations on the pluses and minuses of an aperture stop. My practical experience is that I always bring my aperture stop along, very rarely use it and even less often think the view with it in place is better than the unmasked telescope. I have tried it on the moon, planets and doubles. When observing a more than quarter moon with that scope, the mask is very nice as it cuts down the brightness. The view isn't any "better", just not so incredibly bright. All large dob owners should have an aperture mask and give it a try. Your observing may or may not benefit, but you never know until you try! Mat -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Wednesday, July 10, 2013 7:36 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Off-axis Aperture mask Rich, on nights that won't support a larger aperture, I always go for the small refractor instead of off-axis mask on a larger reflector. I don't see the point in using a huge scope of only 4 to 6 inches aperture. Either that, or observe deep-sky objects that benefit mostly from aperture, and save the close doubles and planets for another night. I'm really liking my Orion ED100mm for backyard observing. On Jul 10, 2013 1:44 PM, "Richard Tenney" <retenney@yahoo.com> wrote:
I have such a mask for my 16" f/6.25 dob -- but have yet to try it out.
In part because I've mostly neglected double stars (and the moon) in my observing sessions. I really need to change that... _______________________________________________ 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". This message and any attachments are solely for the use of intended recipients. The information contained herein may include trade secrets, protected health or personal information, privileged or otherwise confidential information. Unauthorized review, forwarding, printing, copying, distributing, or using such information is strictly prohibited and may be unlawful. If you are not an intended recipient, you are hereby notified that you received this email in error, and that any review, dissemination, distribution or copying of this email and any attachment is strictly prohibited. If you have received this email in error, please contact the sender and delete the message and any attachment from your system. Thank you for your cooperation