Focal ratio of the 9x50 RACI finder objective?

[Nik271]

Hi SGLs,

Does anybody know what is the focal ratio (or the focal distance) of the objective of the Skywatcher 9x50 Raci finder?

I have a spare one and think of converting it to a pocket monocular, just for fun, or maybe a future guide scope. The thread for attaching the prism diagonal looks a standard 2inch SCT female thread and I have a small focuser, but would need to know the spacing needed.

Nikolay

 

 

Edited January 20, 2021 by Nik271

[newbie alert]

The straight through one is 180mm focal length so it be f3.6

You don't need a focuser as the front lens has outward adjustment( Not so sure visually thou)

Think there's a thread pitch difference on the skywatcher and celestron one, dispite them looking exactly the same

[Nik271]

Thanks! 

You were correct that the thread pitch was slightly off:  my focuser only screwed in halfway and then stuck, but its secure enough. With a focuser it's easy to change eyepieces and I can use it as wide field finder/mini-telescope riding on my 180mm Mak.