http://tech.groups.yahoo.com/group/bigdob/ Big dobsonian telescope users. Sat, 19 Jul 2008 03:20:20 GMT gnowellsct http://tech.groups.yahoo.com/group/bigdob/message/18797 http://tech.groups.yahoo.com/group/bigdob/message/18797 these are instructions on how to build an 8" Dobsn telescope http://www.usno.navy.mil/8inchdob.shtml greg n Fri, 18 Jul 2008 23:35:30 GMT alexandrerev http://tech.groups.yahoo.com/group/bigdob/message/18796 http://tech.groups.yahoo.com/group/bigdob/message/18796 Rua Costa Ribeiro, 65 52280-518 (PE) Recife, Brazil Dear American amateur: About Amateur Astronomer's handbook Donation one book to Brazilian poor. I am Wed, 16 Jul 2008 02:36:39 GMT DRLunsford http://tech.groups.yahoo.com/group/bigdob/message/18795 http://tech.groups.yahoo.com/group/bigdob/message/18795 Everyone knows the secondary shadow helps keep the mirror cool by blocking star light :) -drl Tue, 15 Jul 2008 16:31:17 GMT Fabio Falchi http://tech.groups.yahoo.com/group/bigdob/message/18794 http://tech.groups.yahoo.com/group/bigdob/message/18794 Dear friends, I'll be in Boulder, CO, for some time untill August 8. Is there some of you in the vicinity so that we can meet and/or observe together? Fabio Tue, 15 Jul 2008 00:16:13 GMT gnowellsct http://tech.groups.yahoo.com/group/bigdob/message/18793 http://tech.groups.yahoo.com/group/bigdob/message/18793 No, I haven't been paying enough attention. But I cannot be everywhere at once. Thank you for the referral to ExtremeAstronomy. It is not a highly active Mon, 14 Jul 2008 19:20:33 GMT John Mahony http://tech.groups.yahoo.com/group/bigdob/message/18792 http://tech.groups.yahoo.com/group/bigdob/message/18792 You haven't been paying enough attention. I've seen that idea here several times. One thing different about this implementation is that he used velcro to Mon, 14 Jul 2008 18:54:03 GMT Stephen Koehler http://tech.groups.yahoo.com/group/bigdob/message/18791 http://tech.groups.yahoo.com/group/bigdob/message/18791 ... Dave's photos are in the album titled "22 Inch Floating Primary Fan". If I remember right, his fan is suspended by wires and can be attached after Mon, 14 Jul 2008 18:34:13 GMT gnowellsct http://tech.groups.yahoo.com/group/bigdob/message/18790 http://tech.groups.yahoo.com/group/bigdob/message/18790 Well that's interesting indeed. The guy on Yahoo! extremeastronomy (Juan) says that his 2" collimation can still be used because he gets a ring around the fan. Mon, 14 Jul 2008 11:42:43 GMT Mel Bartels http://tech.groups.yahoo.com/group/bigdob/message/18789 http://tech.groups.yahoo.com/group/bigdob/message/18789 ... http://pages.videotron.com/astrolo/buffer/topfan Is this a new thing or am I just late in learning about it????? (aka "finally, a useful application for Mon, 14 Jul 2008 10:45:07 GMT daveleason http://tech.groups.yahoo.com/group/bigdob/message/18788 http://tech.groups.yahoo.com/group/bigdob/message/18788 There's a picture in the photo section of my boundary layer fan posted a few yrs. back. Dave Mon, 14 Jul 2008 04:41:24 GMT Howard Banich http://tech.groups.yahoo.com/group/bigdob/message/18787 http://tech.groups.yahoo.com/group/bigdob/message/18787 Hi Greg, Chuck Dethloff came up with a similar fan arrangement a few years ago, but the fan was mounted on a removable frame so collimation wasn't effected: Mon, 14 Jul 2008 04:34:07 GMT gnowellsct http://tech.groups.yahoo.com/group/bigdob/message/18786 http://tech.groups.yahoo.com/group/bigdob/message/18786 http://pages.videotron.com/astrolo/buffer/topfan Is this a new thing or am I just late in learning about it????? (aka "finally, a useful application for the Mon, 14 Jul 2008 02:46:32 GMT Richard Stember http://tech.groups.yahoo.com/group/bigdob/message/18785 http://tech.groups.yahoo.com/group/bigdob/message/18785 My group (http://socalastronomy.com) has recently started an initiative to donate telecopes (solar and night sky) to middle schools and science instructors. We Fri, 11 Jul 2008 17:33:49 GMT John Mahony http://tech.groups.yahoo.com/group/bigdob/message/18784 http://tech.groups.yahoo.com/group/bigdob/message/18784 ... One source I saw claimed oblate spheroid. drl's argument that it's a sphere sounds reasonable until you add gravity. ... Even if it's a sphere, it's Fri, 11 Jul 2008 16:56:56 GMT Horn, James (GE EntSol, Security) http://tech.groups.yahoo.com/group/bigdob/message/18783 http://tech.groups.yahoo.com/group/bigdob/message/18783 The stretched membrane mirror works fine for non-imaging use. If you want to make a solar furnace, that's one way to do it. When a uniform film is stretched