Re: [ATM] Diagonal Size

[Mark Holm <mdholm@telerama.com>]

You might find it useful to look at Televue's eyepiece specification
chart.  It is at their web site.  Among other things, the field stop
diameter for each eyepiece is listed.  For other vendor's eyepieces, you
can compare, at least roughly, to the Teleview's if the listed focal
length and apparent field (in degrees) are close. (Not strictly true
because apparent field and true field are not the same if there is
significant distortion.  Some of the very wide angle eyepieces have
quite a bit of distortion.)

Also, you may find this little article at S&T helpful
http://skyandtelescope.com/howto/scopes/article_505_4.asp
It refers to a longer article in the August 2000 S&T  You can either buy
an electronic copy of the longer article from S&T, or run out to your
public library and get it for free.  (S&T is found in almost every US
public library.  If they haven't got it locally, they can probably get
it through inter library loan.)  Here is the article information:

Sky and Telescope
August 2000, p. 120-125
Section : "Telescope Techniques"
Title: "Sizing Up the Newtonian Secondary
         Diagonal Calculations with Sec"
Author:  Alan Adler

Mark Holm
mdholm@telerama.com

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