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Name: Terry H.
Status: other
Age: 50s
Location: N/A
Country: N/A
Date: 9/15/2003

How do you compute the theoretical resolving limit (in arc seconds) and the faintest stellar magnitude visible for any given aperture, focal length and magnification? (I am using a 6 inch Newtonian reflector with 1400 mm focal length and a 28mm Plossl eyepiece).

What you are referring to is Dawe's limit, which is determined by the following simple formula:

R' = K / A

where R' is the maximum theoretical resolution in arc seconds

K is the empirically determined constant 4.56

A is the clear aperture (unobstructed effective diameter of the object lens or mirror) in inches.

You may wish to consult the following source:


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