celestron Astromaster 114 focal length

[jonny330]

Something that has always confused me, the focal length of this telescope is always stated as 1m, however the length of the telescope itself is only 50cm. It's just a bog standard Newtonian reflector so the focal length should only be roughly 500mm right?

[brantuk]

Don't forget the focal length extends from the surface of the primary to the focal plane (where you put the eyepiece in to focus). So there's some distance to add to the tube length, from the face of the secondary to where the eyepiece goes. Hth

 

[Knighty2112]

Your telescope is a Jones-Bird telescope design, which allows the telescope tube length to be shorter. Explained better in this link. 

https://en.m.wikipedia.org/wiki/Newtonian_telescope

[jonny330]

11 minutes ago, Knighty2112 said:

Your telescope is a Jones-Bird telescope design, which allows the telescope tube length to be shorter. Explained better in this link. 

https://en.m.wikipedia.org/wiki/Newtonian_telescope

Aaaah yeah that makes sense, awesome, thanks

[brantuk]

Ahh yes - when there's a corrector lens in the focuser tube that would also add to the focus length.

[laudropb]

Basically you have a Barlow type lens included in the light path, which in effect doubles the focal length of the scope.