Tal 100RS 2" Barlow problem

[Coco]

When I try to attach my 2" barlow to my diagonal the scope wont come into focus, I think the only choice I have is to possible shorten the OTA which Ive considered as it would also aid bino viewers?

Has anyone used the 100RS with a 2" diagonal + Barlow + Eyepiece?

[Stephen]

If it was a reflector, I'd tell you you need more back focus with a Barlow.

Is it not the same for refractors?

[Coco]

If it was a reflector, I'd tell you you need more back focus with a Barlow.

Is it not the same for refractors?

It nearly in focus when hard up against the crayford but becomes out of focus when the tube is drawn backwards. This happens with my 1.25 barlow also when in the adapter.

[Stephen]

It nearly in focus when hard up against the crayford but becomes out of focus when the tube is drawn backwards. This happens with my 1.25 barlow also when in the adapter.

What about moving the Barlow to the other side (scope - barlow -diagonal - eyepiece?) Does that change the focal point at all?

(Random suggestion, sorry I don't have an answer)

[John]

TAL refractors can have problems with having enough inward focuser travel. The original TAL100R that I bought back in 1999 had this issue (different focuser to yours though) and the TAL Apolar 125 that I tested a while back could not bring 2" eyepieces in a 2" diagonal to focus at all, never mind with a barlow.

I fear that the solution might have to be to do without the barlow in it, unless you really want to break the hacksaw out.

[Peter Drew]

I've just sawn 2" off the end of a Tal 100RS for a PST mod. Used the mounting ring to mark it off, the focuser mounts over the tube so it is easier to remount it and use the existing holes to spot through.

[Space Beagle]

Same thing with my Tal 100RS, i.e. not enough inward focuser travel for 2" eyepieces, let alone with a barlow! Not too much of a problem for myself as I only have one 2" eyepiece now, the 34mm Meade 5000 SWA. Of course, it works fine if you actually remove the diagonal and just put the eyepiece in the end of the focuser...!

Bloomin' 'eck! I'm not taking a hacksaw to my beloved Tal...!

Doc

[Coco]

Well gents as the OTA was only 150 quid I don't think if its done accurately and properly it would detract to much from the value..

My local machine shop has a band saw with a fine bladed tooth on it at the moment... push a few clean rags up the ota backed up with some tank tape and she'll be fine, its the vibration cutting it that worries me?

I'll have to sleep on it..

.

[AndyH]

If it's simple to put the 'focuser to ota ring' back on the tube, then I'd go for it. Only reason I ask is that the original RS's had an alluminium tube and a machined step where the focuser attached. I've never seen a newer RS stripped down, so don't know how they attach. Would be nice to see a pic.

The bandsaw'll be through it quicker than a quick thing. Take the lens cell off if you're worried about it.

Andy.

[AndyH]

Bizzarely, the new RS's crayford focusers seem to vary in type. One a short version, the other longer.

Short version pic on Astro_Baby's review...........

TAL 100RS Review

Longer version on Dave's example ..................

Stargazers Lounge - F15Rules's Album: Dave's scopes - Picture

Weird but true.........

Andy.

[nightfisher]

I have the newer 100rs, its a steel tube, not ali, mine comes to focus with 2" ep`s and with 1.25 plus barlow, cant comment on 2" plus barlow, looks like they vary some what, good luck with the saw:eek: