http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/ The Nets Premier Telescope Making Group Mon, 09 Nov 2009 01:30:55 GMT Louis Del Sesto http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10596 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10596 I was thinking about a larger aperture like a 12.5 .-14inch but glass this size is huge money .. and i only made 2 mirros so far and i still want to learn and Sun, 08 Nov 2009 19:57:37 GMT lance clarke http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10595 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10595 I'd go for a 12.5" dob as the next scope.  The difference in light grasp between an 8" and 10" is noticable, but not dramatic.  As a rule of thumb, I figure Sun, 08 Nov 2009 16:17:24 GMT trulyyours05 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10594 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10594 Hi Lou, I think Tim's comments are also on the money. A 10" is not a big step up from an 8". It might be better to go for the 12". You would notice a bigger Sun, 08 Nov 2009 04:27:38 GMT tsulmer1 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10593 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10593 Lou, To help you out, here are how the previous posters calculated the magnifications: Focal length of your scope = mirror size (in mm) x focal ratio ie. 10" Sun, 08 Nov 2009 04:26:04 GMT Louis Del Sesto http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10592 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10592 first , thanks starysysn's for your info and AL thanks for your reply Well here it is... My f 5.7 is a awsome scope. I love it ,everyone that looks threw it Fri, 06 Nov 2009 22:06:11 GMT trulyyours05 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10591 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10591 Hi Lou, Starysyn's advice is very good. I would add that you don't normally let a single eyepiece that you have in hand influence your choice of focal ratio Fri, 06 Nov 2009 15:57:40 GMT starryskyn http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10590 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10590 An F10 telescope gives more magnification than an F5 scope with the same eyepiece. The ten inch F10 will have a focal length of 100 inches. With the 25mm Fri, 06 Nov 2009 15:31:08 GMT faintfuzzies1 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10589 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10589 I am new to grinding my own mirror's I made a 8 inch f5.7 with alot of pro help and it came out great but theory is not my strong point and I am sure i don't Mon, 02 Nov 2009 17:42:43 GMT pdebaan http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10588 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10588 A very simple way to calculate the saghitta for a 4" dia. spherometer is 1/focal length. Peter Sun, 01 Nov 2009 17:44:37 GMT http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10587 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10587 Please , Please remember to trim your posts. Some of the posts have been getting way too long as person after person replys to a question. Also please change Sat, 31 Oct 2009 04:04:22 GMT starryskyn http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10586 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10586 http://www.rfroyce.com/cassegrains.htm http://bobmay.astronomy.net/CassNotes/ www.g3pho.free-online.co.uk/microwaves/cassegrain.xls Sat, 31 Oct 2009 03:47:55 GMT exitar01 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10585 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10585 Hey guys, I am starting a new project. I purchased an 8" parabolic cassegrain mirror and cell. I am now gathering all of the all the other parts as we speak Mon, 19 Oct 2009 14:48:24 GMT Mel Bartels http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10584 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10584 Rotate the primary and compare. I doubt that you can see astigmatism in your CCD. More likely you are observing coma due to lack of optical alignment. Mel Sun, 18 Oct 2009 20:28:42 GMT http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10583 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10583 Please , Please remember to trim your posts. Some of the posts have been getting way too long as person after person replys to a question. Also please change Sun, 18 Oct 2009 15:57:09 GMT Ron Dyvig http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10582 http://tech.groups.yahoo.com/group/Make_Your_Own_Telescope/message/10582 Is there an easy way to determine whether astigmatism in a newtonian is due to the primary or the secondary, without removing or shifting either of the