From: Paul Cousoulis 
To: atm{at}shore.net
Reply-To: Paul Cousoulis 


Aperature is everything when determining the performance limits of your scope.

The F number determines your eyepieces.

Some algebra shows.

F#= (primary focal length)/(primary diameter) or
F# * (primary diameter) = primary focal length

Magnification = (primary focal length)/(eyepiece focal length)

Maximum Magnification = 2 * (primary diameter in millimeters)

so
2 * (primary diameter) = (F# * (primary diameter))/(eyepiece focal length)

the primary diameter can be divided out of both sides and rearanging get you.

(eyepiece focal length) = F#/2 for maximum magnification.

So an F8 telescope uses a 4mm eyepiece for its maximum magnification
whether its 3 inch, an 8 inch or 16 inch telescope. Of course the
performance will vary with the primary diameter but an F8 eyepiece set
works with an F8 telescope regardless of the diameter. The eyepiece does
not 'know' how big or how far away the primary is. It only 'knows' the cone
of light the enters it.

Clear skies

Paul

--- BBBS/NT v4.00 MP