Got a Tal mount, but want to use a non Tal scope on it?

[AndyH]

I've got a few different Tal mounts and regularly use my 200K on the 2M mount(MT-2C) and use different non Tal scopes on them.

Here's how I went about it.

Firstly, I'll deal with putting a 200K on the 2M mount.

I'm one of the lucky few, who have early 200K's, some of which came with Tal tube rings. So it's a simple case of attaching the rings to the ota and it'll fit into the slots of the Tal mount, no problem.

If you don't have these rings, then there's two ways to go about it.

1/ If you have the Tal steel dovetail(not to be confused with the saddle that is attached to the ota) that should have come with the scope, then this can be screwed to a length of aluminium or steel flatbar. You'll need a piece 370mm long x 80mm wide plate(the size of the mount plate). All I had to hand at the time was some 5mm thick mild steel flat, which does the job well, but is heavy. Ideally to keep the weight low, I'd prefer to use a piece of 10 or 12mm thick aluminum. Why so thick? To prevent any possible flexure of this plate, when a heavy ota is riding on it. Two holes need to be drilled and tapped about 12mm in from the ends in the middle. I opened out the slots on my mount's top plate, so I could use M8 sized bolts/setscrews. This involved a bit of careful grinding of the slots, as they weren't quite wide enough to accept M8 screw. Next you need to drill two M8 holes on the new plate, in the centre, with a hole spacing of 140mm. There are corresponding tapped M8 holes in the Tal dovetail. Sadly due to clearance issues, you'll need to make a spacer to fit between the dovetail and the new top-plate, to raise it slightly. I used a piece with the following dimensions. 200mm long x 55mm wide x 1.5mm thick. Again, two holes need to be drilled, as per the sizes on the new top-plate, with preferably, slightly bigger holes of approx 10mm.

With two M8 screws, join the top-plate to the saddle with the spacer inbetween. Now bolt this to the mount, again with two M8 screws, from the underside of the mount. Hey presto, one 200K enabled 2M mount.

2/ Another way of mounting a 200K, or/and if you want to put another manufacturers scope on a Tal mount, is as follows.

As per the info in method 1, you'll need a top-plate with the two holes drilled at the ends. Next, you'll need to source a dovetail saddle, like this example here(I use this as an example only. I'm sure there are shops here in the UK that will sell similar ones),

Starway Prismenklemme - GP Level - Basis für Schnellkupplung

Drill and or tap the top-plate, according to the sizes required by the saddle being used. For example, mine needed two tapped M8 holes on the top-plate.

Once the saddle is attached to the top-plate, any scope with a dovetail can now be used on the Tal mount. I now even mount all of my Tal scopes to the mount this way too, by simply adding a dovetail to their rings, or in the case of the 200K, by attaching a std dovetail to the 200K's large steel dovetail. You'd need to alter this std dovetail to fit.

Hope this has been of interest.

Cheers,

Andy.

Some pics, that may help.Bigger pics in my album pages.

Shows the Tal saddle, Tal dovetail, std dovetail, APM(Germany) saddle and mild steel top-plate.

As above.

The spacer used when mounting the 200K's dovetail to the plate. Ignore the std dovetail and APM saddle in this case. I simply don't have a pic of the mount in that configuration.

Small Tal mount with plate n saddle. The size of the plate needed for this mount is 235mm long by 60mm wide.

[AndyH]

Time for an update to this thread......

A couple of months back I replaced my mild steel top plate with an aluminium one. I find it to be far more ridgid, especially when the DEC shaft is horizontal to the ground and the mount is carrying a large heavy load.

Some pics to help.....

I ended up getting 15mm thick alu plate. Sizes and centre to centre hole spacings as per the original post(The two unthreaded M8 holes with 140mm spacing may, depending on your accuracy, need to be increased to say 8.5mm diameter). The two M8 setscrews attaching the plate to mount should ideally be 30mm long. Preferably use washers to protect the mount.

When using 15mm thick alu plate, a spacer, as described in the original post, is unnecessary. I'm not totally sure, but have summised that when the mild steel plate was screwed down to the mount, the plate bowed, thus causing the saddle on the Klevtsov to stick on it, as I tried to move it along the dovetail.

M8 setscrews attaching the Tal dovetail to the plate. Minimum of 20mm long. They attach from the underside.

M8 Countersunk setscrews, 15mm long, attach the saddle to plate.

If you are tight on budget or cannot get hold of a saddle, you can simply drill another two holes on the plate, to allow you to attach other manufacturers tube rings direct, without using a dovetail.

Why?

Other manufacturers tube rings are wider than Tal's, so cannot fit into the slots on the bare mount top plate, as Tal rings can.

Hope this is of some help.

Cheers,

Andy.

[AndyH]

I've altered the way things screw to the alu plate. I got fed up having to take the whole plate off to get at the bolts/setscrews, to remove the Klevtsov dovetail.

Much easier if it can screw on, with the alu plate in place on the mount. The dovetail is threaded for M8. If you've ever tried to screw together two items that are both threaded, you know that it's virtually impossible for them to sit tight together. The only option is to use 'captive bolts'. Rather than trying to source a couple, I put a std M8 bolt into an old hand drill, secured it, switched on and using a heafty file, removed a portion of it's thread from the base(next to the hex head). Only recommended if the drill is old and not used much. Doing this mod, cannot be good for it's internal bearings and such. Of course if you had a small lathe, removal of a portion of the thread would be a simple task.

Once done, I screw the modified bolts to the Klev dovetail, then to threaded holes on the alu plate.

So now if I want to use a scope with a std dovetail, off comes the Klev dovetail and on goes the universal fitting saddle.

If you google 'captive screws' or 'captive bolts', there should be a range of images that'll show what they look like.

Andy

ps: reg the 1st post: I guess when there was a forum software change, some images were lost.

[jason.p]

Cheers Andy. I'm looking around for some 12 or 15mm aluminium plate, it's not as dear as I thought it would be. The OTA may have to wait a bit. A nice cheap 200K would do (dreaming again )

Jason

[AndyH]

When I buy aluminium in larger quantaties I use http://www.raaltd.com/aluminium.htm

When it's just small bits n pieces, I find these guys http://stores.ebay.co.uk/Forward-Metals-Ltd

give excellent service and good prices. They'll also cut to size and do so with very good accuracy.

Andy.

[jason.p]

Thanks for links

[jason.p]

I never did find a cheap 200k, but a nice 200p.

Following Andy's instruction I've now got it mounted on my TAL mount (thanks Andy).

The aluminium plate is 12mm.

The saddle is from FLO (thanks for help Martin)

Just need to fix the Telrad, and maybe look out for a finder. I'm away for a while, so first light will have to wait.

Thanks again Andy for your advice

Jason

[AndyH]

Nice mod, Jason !!