· 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 droid rocketman Reged: 08/29/04 Posts: 4047 Loc: ohio basic info       #3359309 - 09/27/09 09:11 AM Edit   Reply   Quote Quick Reply   Ok I know that my mirror will be 13 inches in diameter. I also know it will be rouhgly F/5 Question #1) If I got with a solid tube ,what inside diameter???? Question #2) What size secondary? strictly visual use. -------------------- 12 inch Truss Reflector "John" 102mm Celestron C102HD Tasco 7TE5 60mm Classic Tasco 9TE5 60mm Classic Celestron Ultima 2000 SCT Remains of an 8 inch dob Celestron Comet catcher(orange tube) 1960 Edscorp Space Conquerer 6inch f/8 10x50 Bushnell Binoculars. 11T 4.5 inch Tasco reflector Lunograsso? 60mm Telescope Club Post Extras:       Luigi Post Laureate Reged: 07/03/07 Posts: 4947 Loc: MA Re: basic info [Re: droid]       #3359341 - 09/27/09 09:32 AM Edit   Reply   Quote Quick Reply   Newt answers all. -------------------- 17.5" f/5 Dob. IM-715 MCT. 120ED. Lunt 60mm Ha. Zeiss, Leica, Fujinon, Nikon, Pentax, Bushnell bins Post Extras:       droid rocketman Reged: 08/29/04 Posts: 4047 Loc: ohio Re: basic info [Re: Luigi]       #3359398 - 09/27/09 10:08 AM Edit   Reply   Quote Quick Reply   ok, focuser height , racked in or racked out?? -------------------- 12 inch Truss Reflector "John" 102mm Celestron C102HD Tasco 7TE5 60mm Classic Tasco 9TE5 60mm Classic Celestron Ultima 2000 SCT Remains of an 8 inch dob Celestron Comet catcher(orange tube) 1960 Edscorp Space Conquerer 6inch f/8 10x50 Bushnell Binoculars. 11T 4.5 inch Tasco reflector Lunograsso? 60mm Telescope Club Post Extras:       HiggsBoson Pooh-Bah Reged: 02/21/07 Posts: 1118 Loc: Kal-li-fornia Re: basic info [Re: droid]       #3360403 - 09/27/09 08:10 PM Edit   Reply   Quote Quick Reply   racked in. -------------------- Michael ATM: 6" F/9 Newtonian Travel Scope ATM: 12.5" F/4.5 Real Soon Now... Post Extras:       droid rocketman Reged: 08/29/04 Posts: 4047 Loc: ohio Re: basic info [Re: HiggsBoson]       #3360714 - 09/27/09 11:02 PM Edit   Reply   Quote Quick Reply   OK got it all done......how do I save it? -------------------- 12 inch Truss Reflector "John" 102mm Celestron C102HD Tasco 7TE5 60mm Classic Tasco 9TE5 60mm Classic Celestron Ultima 2000 SCT Remains of an 8 inch dob Celestron Comet catcher(orange tube) 1960 Edscorp Space Conquerer 6inch f/8 10x50 Bushnell Binoculars. 11T 4.5 inch Tasco reflector Lunograsso? 60mm Telescope Club Post Extras:       astro744 member Reged: 09/22/07 Posts: 73 Re: basic info [Re: droid]       #3361159 - 09/28/09 06:13 AM Edit   Reply   Quote Quick Reply   Also look at http://www.bbastrodesigns.com/diagonal.htm Likely 2.6" or 2.14" diagonal but many factors come in to play. A 2.6" will give you 20% contrast obstruction and a nice large fully illumunated field of view should you wish to use low power eyepieces with large field stop diameters. However, exit pupil will be large at f5 so your largest eyepiece is likely to be a 31mm Nagler which has a field stop diameter of 42mm (R=21mm or 0.83"). Note a brighter larger field is needed for variable star observing so as not to have a magnitude drop at the edge of field. Contrast is less important if designing for variable star observing and a larger than usual diagonal is needed. The idea of Mel Bartels program is to match the off-axis radius with the field stop diameter/2 of your lowest power (or most used lowest power) eyepiece. eg. 31mm Nagler has field stop diameter of 42mm (R=21mm or 0.83"). You want the 70% illumination to be at the 21mm off-axis mark. If your lowest power eyepiece is say a 27mm Panoptic with field stop diameter of 30.5mm (R=15.05mm) then aim for 70% illumination at the 15mm off-axis mark or 100% illumination at the 15mm off-axis mark if you observe variable stars. The size of the diagonal and distance to focal plane are the two parameters you can tweak so you need to consider what type of focuser you will be getting. The program NEWT mentioned in another post also looks at vignetting. I find too many people size their diagonal too small and do not have sufficient off-axis illumination in their low power eyepieces and this can have considerable impact when observing galaxy clusters (eg Virgo, Fornax) where the galaxies are all over the field and not just in the middle and a 0.5mag drop toward the edge can mean the difference between seeing a faint fuzzie and not seeing one. As long as your contrast ratio is 20% or under you are fine for good planetary observing too. Post Extras:       droid rocketman Reged: 08/29/04 Posts: 4047 Loc: ohio Re: basic info [Re: astro744]       #3361240 - 09/28/09 07:54 AM Edit   Reply   Quote Quick Reply   Actually 2.3 inches heres what I got so far: diagonal offset- .1150 100% illumination diameter - .4966 75% illumination diameter - 1.4343 Front aperature diameter - 14.494 ??? mirror face to focuser hole - 55.625 inches, Im assuming thats to the center of the hole to allow me to measure where to cut out the hole??? focuser to front of tube - bit of a mystery as Newt seems to think Im going ot buy a tub 6 feet 3.5 inches long.Mine will be 6 feet even. 13 imch mirror F/5 (65.0 inches focal length) tube inside diameter 14.5 inches focuser height racked in 2.0 inches /2 inch diameter -------------------- 12 inch Truss Reflector "John" 102mm Celestron C102HD Tasco 7TE5 60mm Classic Tasco 9TE5 60mm Classic Celestron Ultima 2000 SCT Remains of an 8 inch dob Celestron Comet catcher(orange tube) 1960 Edscorp Space Conquerer 6inch f/8 10x50 Bushnell Binoculars. 11T 4.5 inch Tasco reflector Lunograsso? 60mm Telescope Club Post Extras:       Pages: 1 Previous   Index   Next   Threaded   Extra information 6 registered and 7 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: 218 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

Cloudy Nights Sponsor: Astronomics