It would seem at first blush that if you have a telescope with a given focal length producing x magnification and you then viewed that image through 2 eyepieces of different focal lengths, that the eyepiece with the longer focal length would yield the higher magnification. What makes it work opposite of what one (I) would expect?
I know this is a basic optics question that I'm just not too embarrassed to ask.
Tom C.
From: "Herb Chong" <[EMAIL PROTECTED]> Reply-To: pentax-discuss@pdml.net To: <pentax-discuss@pdml.net> Subject: Re: Astrophotography (was Re: *istD EOL...) Date: Wed, 12 Jan 2005 20:48:29 -0500
short focal length on an eyepiece gives high magnification. total magnification is the focal length of the objective divided by the focal length of the eyepiece. if 900 is the objective FL, then the 20mm eyepiece gives 45X and the 4mm eyepiece gives 225x.
Herb... ----- Original Message ----- From: "Nick Clark" <[EMAIL PROTECTED]> To: <pentax-discuss@pdml.net> Sent: Wednesday, January 12, 2005 1:28 PM Subject: Astrophotography (was Re: *istD EOL...)
> I got a telescope for Christmas with a camera adaptor. I've not had much chance to play with it yet but was quite impressed with its power the first couple of times I used it. It's a Telstar 900x114 reflector, and fills the eyepiece with the moon with the 20mm objective. Strangely the moon is even larger when using the shorter focal length 4mm eyepiece, which I haven't quite worked out yet.
