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: <[email protected]> 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.
