Back to Home

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
Which Is Best?

Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response To
Posted by Robert May on October 13, 2002 19:50:35 UTC

The planetary scopes tend to be longer FL scopes as you need to build magnification to see the planets. You're pretty much limited to 50x/in. of magnification so your scope will easily achieve 400x. You can build a scope with a long FL and get the high magnification with a nice EP while a shorter scope will be needing a much shorter FL EP to get the same magnificaion.
On the other hand, many of the deep sky objects out there are on the order of a degree in diameter or larger and thus you need to have a shorter FL scope so you can see all of the object.
Simple geometric math on the central ray will show that as the FL grows, the EP needed to see something grows larger in diameter as well as a larger FL for the EP to maintain the magnification.

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