· Get a Cloudy Nights T-Shirt · Submit a Review / Article    Click here if you are having trouble logging into the forums Cloudy Nights - Official Forums of the 2009 International Year of Astronomy Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu.... uh, User   You are not logged in. [Login] Forum Archives · Entrance · Main Index · Search · New user · Who's Online FAQ · Calendar Equipment Discussions >> ATM, Optics and DIY Forum Previous   Index   Next   Threaded   Pages: 1 mattyfatz Pooh-Bah Reged: 12/27/06 Posts: 1297 Loc: Boise Idaho Cassegrain Primary into a Newt?       #3402239 - 10/21/09 01:48 PM Edit   Reply   Quote Quick Reply   Can an SCT or MAK primary be used for a rich field newtonian primary? Will the coma be too much to bear? Has anyone done this in the past? thanks. Matty -------------------- **Matty** Stimulating the economy, one piece of equipment at a time. Post Extras:       DAVIDG Carpal Tunnel Reged: 12/02/04 Posts: 1990 Loc: Hockessin, De Re: Cassegrain Primary into a Newt? [Re: mattyfatz]       #3402395 - 10/21/09 03:09 PM Edit   Reply   Quote Quick Reply   Usually the primary in both SCT or a Mak is spherical so at f/4 or less, the spherical abberation will be huge. Only a classical cassegrain uses a parabolic primary that would work in a Newtonian. A dual focus cassegrains use a removal secondary that is replaced with a newtonian diagonal so the telescope can be used both as a high and low power system. I believe that both Cave and Starliner sold commerical versions of this setup. - Dave -------------------- Homemade 'scopes 8"f/7,6" f/5", 6"f/4, 4.25" Schief. 60mm Coronagraph,60mm H-alpha system, 4.25" White-light Solar Newtonian,solar spectroscope, 4.5" f/16 Schupmann Medial refractor, 14 Stellafane awards 7 in optics Engineering = Taking what you have and making what you need. Post Extras:       gregj888 sage Reged: 03/26/06 Posts: 303 Re: Cassegrain Primary into a Newt? [Re: DAVIDG]       #3402851 - 10/21/09 06:37 PM Edit   Reply   Quote Quick Reply   Matty, There are designs with correctors at various places, but you pretty much need a corrector of some sort. Houghtons, Wrights both have full App. correctors and both would be better at F/4 than f/2 (most SCTs at at F/2). Several field corrector designs are also around. Sorry, no names off the top of my head. Greg Post Extras:       mattyfatz Pooh-Bah Reged: 12/27/06 Posts: 1297 Loc: Boise Idaho Re: Cassegrain Primary into a Newt? [Re: gregj888]       #3403009 - 10/21/09 08:15 PM Edit   Reply   Quote Quick Reply   Thanks for the advice -------------------- **Matty** Stimulating the economy, one piece of equipment at a time. Post Extras:       Pages: 1 Previous   Index   Next   Threaded   Extra information 1 registered and 3 anonymous users are browsing this forum. Moderator:  Don W, Mike I. Jones  Print Thread Forum Permissions       You cannot start new topics       You cannot reply to topics       HTML is disabled       UBBCode is enabled Thread views: 141 Jump to *International Year of Astronomy 2009* -----   Global Coordination   Cornerstone Projects   Special Projects   Special Task Groups   Global Activities   National and Regional Activities   IYA 2009 in Africa   IYA 2009 in the USA*Announcements and News* -----   Cloudy Nights Announcements   Discussion of CN Articles, Reviews, and Reports   Beginners Forum   Celestial Events   Light Pollution*Equipment Discussions* -----   ATM, Optics and DIY Forum   Binoculars   Binoviewers   Cats & Casses   Classic Telescopes   Equipment   Eyepieces   Mounts   Observatories   Reflectors   Refractors    Celestron SkyScout and Meade mySky   Video and Electronically Assisted Astronomy*Astrophotography and Sketching* -----   Beginning and Intermediate Imaging   Film Astrophotography   DSLR & Digital Camera Astro Imaging & Processing   CCD Imaging & Processing   Solar System Imaging & Processing   Sketching   Astro Imaging/Sketching Contest *Observing* -----   NEO   General Observing   Planetary and Solar System Observing   Lunar Observing   Deep Sky Observing   Double Star Observing   Solar   Variable Star Observing and Radio Astronomy*Telescope Specific Forums* -----   Celestron NexStar    NexStar GPS / CPC Telescopes   Questar Forum   Meade ACF/RCX / LX / GPS    Meade ETX*Other* -----   Science of Astronomy & Space Exploration   AstroWebsites   Space Rocks*Speciality Forums* -----   AstroArt   Astronomy Software & Computers   Stellar Media   Astro Outreach, Clubs and Star Parties*CN Feedback and Vendor Announcements* -----   Vendor and Group Announcements CN Forums Home

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