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Novice Challenge

RAS thread adaptor

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I have an old brass telescope that can be used for both terrestrial and astronomy viewing. However, the lens capsule at the end of the terrestrial eyepiece assembly is an odd size.

Removing the terrestial assembly reveals a 1.25inch RAS female threaded housing that is brazed onto a 1.25inch od brass draw tube that goes into the rack & pinion unit.

I would like to use a webcam and standard lens with my telescope.

So, does anyone know of an adaptor that has a RAS male thread at one end and a 1.25 inch female socket (or T thread) at the other end?

Any and all suggestions welcome



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  • 8 years later...
On 27/01/2015 at 11:36, Astrobits said:

The RAS thread is BSP ( British Standard Pipe ) so just get a couple of bits of pipe and find someone who could turn one bit down to 1 1/4" push fit.


I know this is an old thread (no pun intended) but just for info RAS thread is 1 1/4" 16 tpi BSP threads are 11 tpi.


So RAS is not BSP.

They look similar and you may be able to force the threads together (cross threading and possible damage) but they arent the same.

I am in the process of making a couple of adapters at the moment and found this thread again whilst checking.

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