jeyjey wrote:
Michael --
That Moonlight adapter is quite a bit shorter than the Starlight Instruments one, and the whole setup is quite a bit shorter than my Van Slyke was. I'd guess you're at 4200mm to 4250mm.
As you say, though, the only real way to know is to time a star drift or compare fields to a planetarium program.
Cheers,
-- Jeff.
I took a look at the Moon this evening with the 22mm nagler and compared the FOV to Virtual Lunar Atlas.
I reckon the focal length of the scope is approx. 4,350mm with the diagonal and Moonlite focuser in place.
If I position a Celestron f/6.3 focal reducer between the eyepiece and diagonal, I get the equivalent of approx 3,730mm focal length.
This is equivalent to using a Nagler of 25.6mm focal length with just the diagonal and Moonlite focuser.
Alternatively, If I position the Celestron f/6.3 focal reducer between the diagonal and Moonlite focuser, the focal length becomes approx. 1870mm
This is equivalent to using a Nagler of 51mm focal length with just the diagonal and Moonlite focuser.
Alternatively, if I position the Celestron f/6.3 focal reducer in the scope-end of the drawtube of the Moonlite focuser, the focal length reduces down even more.
However, the image quality also degrades significantly and so I wouldn't use it for obserbing with a diagonal and eyepiece in this configuration.
May be more appropriate with just a camera on the back (no diagonal) in this configuration.
Interesting how the focal length can change so much in a SCT depending on the optical and other accessories which are used.
Michael.
  