I'm building a planetary Newtonian for the Mars opposition around an 8" f 10 full-thickness mirror. If I use a 9" or 10" tube with a 1.25" low profile focuser, what would be the optimum size for the diagonal mirror? I have a 3 curved vane spider and 1.25" M.A. 1/20th wave diagonal, but would it be advantageous to use a smaller one? This is going to be a dedicated planetary scope.
Re: About secondary mirrors
Started by jadamslh, 03/22/2003 09:06PM
Posted 03/22/2003 09:06PM
Opening Post
Posted 03/23/2003 12:57AM
#1
James,
Your 1.25" secondary is a 16 percent obstruction. Using a .75" secondary will be a 9 percent obstruction. Your focuser will have to be at least 2.5 inches and you need a 9 inch tube. Your secondary holder needs to be the same size as the secondary or smaller. You alraedy have a 1/20 wave secondary. You would have to consider that in your decision. But its, as far as I can tell, do-able.
Your 1.25" secondary is a 16 percent obstruction. Using a .75" secondary will be a 9 percent obstruction. Your focuser will have to be at least 2.5 inches and you need a 9 inch tube. Your secondary holder needs to be the same size as the secondary or smaller. You alraedy have a 1/20 wave secondary. You would have to consider that in your decision. But its, as far as I can tell, do-able.
Funding Member
Sponsors
- Optique Unterlinden (Europe)
- Anacortes Telescope
- AstroMart LLC
- Pier-Tech Inc.
- Astromart Customer Service
- Matsumoto Company
- SellTelescopes.com
- GetLeadsFast, LLC
- Clearline Technology Corp.
- T.E.C
- ADM
- Rod Mollise
- Takahashi
- GetLeadsFast, LLC
- AG Optical Systems
- AstroMart
- SkyShed Observatories
- Starmaster Portable Telescopes
- FocusKnobs
- APM-Telescopes
View all sponsors