Happy Halloween

ATM Forum Message

Forums: Atm · Astrophotography · Blackholes · Blackholes2 · CCD · Celestron · Domes · Education
Eyepieces · Meade · Misc. · God and Science · SETI · Software · UFO · XEphem
RSS Button

Home | Discussion Forums | Amateur Telescope Making | Post
Login

Be the first pioneers to continue the Astronomy Discussions at our new Astronomy meeting place...
The Space and Astronomy Agora
Re: Secondary Mirror Size

Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response To
Posted by Walter Hamler on January 25, 2001 21:12:48 UTC

I plugged the numbers into my copy of NEWT 2.5 and came up with the following: With a 1.5" the 100% illuminated area will be 0.14" dia. and the 75% illum area will be 0.88". This would be acceptable for 1.25" eyepieces and lunar/planetary work.
Moving up to the 1.83" would give 0.54 and 1.25" respectively, but would necessitate a 2" focuser to prevent vignetting. The contrast difference would not be noticible I would think. Personally I'd go for the 2" focuser and the 1.83" secondary.

Walt Hamler

Follow Ups:

    Login to Post
    Additional Information
    Google
     
    Web www.astronomy.net
    DayNightLine
    About Astronomy Net | Advertise on Astronomy Net | Contact & Comments | Privacy Policy
    Unless otherwise specified, web site content Copyright 1994-2021 John Huggins All Rights Reserved
    Forum posts are Copyright their authors as specified in the heading above the post.
    "dbHTML," "AstroGuide," "ASTRONOMY.NET" & "VA.NET"
    are trademarks of John Huggins