Tal - help with balancing

[TheThing]

I have a Tal 2M mount but no instruction manual with it. My 6" has never been a problem on it, but now I want to use an 8" SW 200 which is much largerheavier.

Can someone with instructions let me know how to balance it properly please? Is there a way of disengaging the motor to do this? Would it be possible to get a copy of the manual at all?

[Merlin66]

the astroscopic labs - review: Newton Reflector equatorial TAL-2M ( appr. € 850,- )

It mentions need the end of the article how to re-adjust the RA clutch...might help you

[AndyH]

Hi.

Balancing in the DEC arm is easy enough as I'm sure you know. With the ota horizontal to the ground, just loosen off the smaller tension knob and move the ota in the rings to suit, then re-tension the knob, so it's tight enough that the slo-mo knob moves the ota without slippage, but still moveable by hand.

The RA arm is slightly more problematic due to the large clutch plate. Again with the RA arm horizontal, loosen off the 3 screws on the large clutch plate and with a hand on the ota and the other on the weight bar, swing the arm to and fro, the best you can. Move the weights up or down the bar to suit. Because of the clutch, you're never going to get the RA arm moving totally free and easy. Once you think the balance is right, tighten up those 3 screws again. You'll know it's right when you try moving the RA arm with the RA slo-mo knobs and there's no slippage. Keep an eye on the RA setting circles. You'll see any slippage easily then. Again, don't tighten the 3 screws too much or you'll making hand movement of the scope too hard. Always attempt this with the scope and then the RA arm's weights coming up to the horizontal.

If you notice a judder at any time in the movement then this is a sign of the worm needing to better meshed with the brass gear. The plastic slo-mo knob on the side opposite to the on off switch needs to be removed and the 4 small screws holding the bearing and worm lossened. Insert a screwdriver into the slo-mo knob's screw hole and pull up with a little bit of pressure. Whilst doing this you'll need to start tightening the 4 screws. You don't want the meshing of worm and gear too tight, but not too loose either, or the RA arm develops some 'play'.

Throughout a session, I always periodically check the RA clutch screws to make sure they haven't loosened ever so slightly, which can happen if you're moving the scope around the sky a lot. So I keep a long screwdriver to hand.

With the extra weight on, you may need to tighten the motor clutches 3 screws. To test for motor gear slippage, set the RA arms setting circles to zero and switch on the motor. Leave it for an hour. If the setting circles haven't moved by an hour, then there has been some slippage and a slight tighting is required. Do the aforementioned job with the RA arm in the horizontal position again as this is the most stressful time for the motor clutch. Any slippage shows up then. In fact if there is obvious slippage of the motor gear, you should be able to see it, straight away, by looking in the back of the mounts housing.

I appologise in advance if any of the above is obvious. Thought it best in case any one else out there is reading this and wants to tune up his or her 2M mount.

Hope this helps,

Andy.

[AndyH]

As a side note, and aimed at no-one in particular.........I've always seen the 2M mount as being like a dob !! As it has no locking levers on either the RA or DEC, with the motor running you can move the scope by hand around the sky. Totally ingenious, thanks to the clutches. I've tried other mounts, including the newer stepper motor MT-3S Tal mount(which is great, but has locks on the axis) and always miss this 'dob' feature on my 2M mount. I suppose it helps when it can carry 20kg. That's a bonus.

Cheers,

Ash.

[TheThing]

Thanks Gents, very helpful.

I never knew you could dob the mount with the motor running. I always switch it off and back on again after moving by hand.

[AndyH]

Yup.

Only time I switch the motor off is when I want to use the RA slo-mo knobs. So I swing the mount about with the motor on, then when I reach for the RA knobs, to finely centre the object, I click off the motor. In theory, the motor could be left on, even whilst using the knob, but with the vulnerable motor gearbox(not to be confused with the motor clutch gear), I like to be safe than sorry.

I think most, if not all, cases of motor gearbox failure is due overtightening of the clutch and the subsequent use of the knobs with the motor running. Mind you, this overtightening can be unavoidable if the mount is carrying a lot of weight.

I've seen pics and had gearboxes with the final gear being made of steel, brass and a form of hard plastic. Having taken one completely to bits, it's easy to see how they can be stripped.

Always best to err on side of safety. But there's never a problem with moving the scope by hand.

Cheers,

Andy.