Along with commercial units using thick vanes, I've seen homemade curved vane spiders made from thick material. Wanting to avoid that, I went with the method of using stainless steel rulers. Bad idea. They are just too thin to not wiggle like the MaryJane Girls. Don't go the stainless steel ruler route if you want to make your own curved vane spiders. I learned that lesson! Mat -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Thursday, March 08, 2012 1:23 PM To: Utah Astronomy Subject: [Utah-astronomy] Diffraction effects of secondaries and spiders (Was: solar filter) All of the curved vane commercial spiders I have seen use very thick vanes, as a way to eliminate vibration. They actually decrease the throughput to the primary over a straight-vaned spider and increases overall diffraction.