TAL bargain on bay

[bambuko]

...It's not as if it's a particularly weird thread size...

you would have thought so , wouldn't you?

au contraire - 42x1 seems to be as rare as hen's teeth

Good links and plenty of inspiration - thanks.

My cunning plan didn't involve thread cutting - after all I already have 42x1 adapter.

My plan is to modify it, by brazing suitable lump of metal at eyepiece end.

ps don't worry about your mental state - after all, you are already amongst us, in the asylum - you are safe

[AndyH]

Yeah. Brazing on a piece, then machining it up to suit, is the best option and the one I'd go for if I had the tools.

The 'only' downside is, the included 32mm accessories will be unusable, unless you shave 0.25mm off their nosepieces. Do-able? If the barlow is in good condition and throws up good views, it too would need a bit of alteration at both ends, if you see what I mean.

Something to mull over.

No matter what you decide, if you're happy, then it's worth doing. Simple as that. As I've found when totalling up the costs, on various potential projects, getting multiple adapters can be an expensive game !!

Cheers,

Andy.

[bambuko]

Yes I have few 32mm pieces gathering dust, long since replaced by 1.25" pieces.

Talking about Barlow...

It is the usual x4 that was part of the kit.

What is your opinion about it?

x3 that I acquired with Tal-1 was very disappointing

[AndyH]

The (yr2000) 4x tal barlow was mechanically superior to any other Tal barlow I've had, with a compression ring similar to the one on the 2M's R&P focuser. Optically I found it to be decent, but not earth shattering. The 2x is the best of the bunch. In fact a few months back, Bill Paolini did a test alongside a TeleVue 2x and concluded it was at least as good, optically.

The 2x can be converted to a 3x by adding a 56/57mm spacing  sleeve between it and the eyepiece. Tal sold this item at one time and included it with the accessories that came with their 75R frac. Varying the length can get you to a multiplication that suits your eyepieces. I don't think I'd want to push it above a 3x.

Andy.

[bambuko]

Just my luck ... the only decent one is the one not in my collection

I have x3 and x4 but not x2

Thanks for that summary - I will know what to look for.

[bambuko]

Solved the problem:

Bottom end is original 32mm adapter with 42x1 thread, suitably shortened.

Top end is from x3 TAL Barlow - removed the optics and turned inside to suit original adapter.

Glued together (bottom end is steel, top end is aluminium, so couldn't braze).

Compression ring fitting for eyepieces is a bonus

I am beginning to look forward to some nice weather...

[bambuko]

Bit of a disappointing night   

Don't seem to have enough "in" travel in the focuser (and that despite already making it shorter by about 12mm when compared with original 32mm eyepiece adapter)

I guess it is the same problem that afflicts old TAL-1 when used with 1.25" eyepieces (Russian 32mm eyepieces seem to have different design).

I might have to do some experiments, but that will have to wait for daylight...

[AndyH]

Could always replace the old primary mirror springs with longer, stronger ones. Even if I don't need longer, I've replaced the springs on all my Tal newts with stronger(thicker wire diamater) ones.

I don't have access to the place I got my springs in the past, as my main pc needs a new PSU, but this place looks promising for sourcing springs......

http://www.entexstocksprings.co.uk/index.php?route=common/home

Cheers,

Andy.

[bambuko]

Thanks Andy,

moving main mirror is always an option (see my TAL-1), but a bit drastic and un-necessary on TAL-2.

There is enough room in eyepiece adapter to take some length out.

Luckily my original (made out of two pieces) adapter was only glued topgether:

Gentle application of heat and Loctite comes un-done:

Quick 7mm off and re-glued adapter looks like it was made originally in the factory:

Just what the first secretary of communist youth league ordered

[bambuko]

Heavy fog descended before I could do any serious playing with my modified TAL, so it was back to the workshop.

I can't justify 4 different telescope mounts (not enough space for all my toys) so decided to standardise on TAL-2M mount for all my scopes.

First one to be adapted was my Skywatcher 150

and with the scope in it:

Pretty happy with this... my EQ3-2 is advertised for sale

Next one will be fitting of TAL-1 on TAL-2M mount.

Maybe I am wrong, but I am working on the assumption that I can only observe through one scope at a time, so plan to use one mount for my three different reflectors.

[bambuko]

Just to confirm (now that I had a chance to test full range of eyepieces from 32mm to 4mm) - I ended up taking out 19mm (3/4") from the length of eyepiece adapter, when converting from old soviet 32mm dia eyepieces to the standard 1.25" dia.

I can focus all my eyepieces easily now.

So if you get pre 1999 old soviet reflector and want to use it with your standard eyepieces that is what you will have to do.