Custom helical focuser EP holder

[badhex]

Hello all, 

I would love to give my old Charles Frank 6" reflector a new lease of life, however being the age that it is, it accepts only 0.965" or RAS threaded EPs in the helical focuser. I do have a collection of decent 0.965" EPs but would love to use modern EPs in it as well. 

Since it is a newt, a 1.25" adaptor will not work here as there is not enough in focus to account for the adaptor. I also don't really want to replace the whole focuser, as it also mounts the WW2 gunsight which it has for a finder!

In light of this it occurred to me that perhaps I could actually get a new focuser EP holder part made with say a T2 connection on the end, allowing for connection of modern adaptors, EP holders etc. 

I think it might actually be quite simple to make. Here is the existing focuser tube plus RAS-0.965" adaptor:

 

I don't have my thread gauge and calipers to hand but essentially, it would need to be a tube of probably about 1.5" diameter, threaded on the outside (my guess is a fine imperial thread of some sort). Towards the top I'd need a wider collar to grip for focusing, and then finally T2 threaded for whatever EP holder or accessory I decide upon. 

So, who could I speak to who might be able to do this? Beacon Hill might be an option I think if they are still going, though I haven't been able to get in touch yet. I don't know anyone else who might have the required equipment to do it. 

If anyone has suggestions, maybe someone here who has the skill to make such a thing, I am all ears! 

 

[Peter Drew]

I would turn out the threads of the RAS thread fit to accept the 1.25" eyepiece fit.     🙂 

[badhex]

4 hours ago, Peter Drew said:

I would turn out the threads of the RAS thread fit to accept the 1.25" eyepiece fit.     🙂 

Thanks Peter, I know that it would not be much work given how close RAS is to 1.25". That said, I don't have the required tools, plus I'd like to not modify the original focuser really. 

I was actually hoping you might reply given your vast experience. Do you think what I'm suggesting as an alternative would be possible?

[Peter Drew]

I too, prefer not to permanently modify an original part if at all possible.  Unfortunately it would be the only solution to use the existing item.  Making a new component as you suggest would certainly be a way forward if you can find a suitable facility.  Another option would be to advertise for a spare focus tube and have the eyepiece threads turned out as per my original suggestion.    🙂

[badhex]

2 hours ago, Peter Drew said:

I too, prefer not to permanently modify an original part if at all possible.  Unfortunately it would be the only solution to use the existing item.  Making a new component as you suggest would certainly be a way forward if you can find a suitable facility.  Another option would be to advertise for a spare focus tube and have the eyepiece threads turned out as per my original suggestion.    🙂

Cheers Peter. I hadn't thought about finding a spare, although I'll admit I'm not hopeful! Despite their popularity at the time (or so I understand) there seem to be very few in the wild these days. Maybe I should start a Charles Frank owners club here on SGL!

At any rate, I have now managed to track down Barry from Beacon Hill and we had a really nice long chat this morning, partly about my request and partly just about vintage scopes, craftsmanship etc. I name dropped you Peter as I assumed you probably knew each other! He thinks it shouldn't really be a problem to make what I'm after, though we agreed I'd send either the whole focuser or the focuser tube over to him so he can check tolerances etc. Hopefully this should be a great opportunity to breathe a bit of life back into a venerable scope!