Adjusting and tuning up your Tal mount

[AndyH]

Adjusting and tuning up your Tal mount

First things first. The Tal mounts are not like standard eq mounts.

Standard eq mounts like the EQ5, etc, etc, have axis locks in both RA and DEC, so that you unlock the lever and move the scope to near the target and then lock the lever again.

The Tal mounts do NOT have/use this system, unless you have one of the newer stepper mounts(MT-3S -- Don't think there's that many of them here in the UK)

The Tal's rely on a clutch in the RA axis and a sleeve with adjustable clamping collar on the DEC.

On the DEC axis, up on/close to the ota mount plate, the smaller of the two knobs is the tension screw/knob. It can lock the DEC axis, or ideally, tighten it just enough to hold the scope in position, without it slipping, but still let the user hand push the scope around on that axis. The bigger, slo-mo knob can then be used to get the object bang in centre of the eyepiece. Bear in mind that this has a limited amount of travel, so before each viewing session, the wheel should be wound to approx halfway.

Here's a guide to setting up any Tal mount in DEC, either with a motor drive or a manual one.

Loosen either the long black lever or large black handwheel, that locks the latitude of the RA axis. It may be tight. If so use a piece of tube(or similar) over the lever, for extra purchase. Set the latitude to 0, so the RA axis is horizontal to the ground. Now hand tighten the latitude lock lever or wheel. Move the DEC axis so that it is also horizontal to the ground. Lock the tension knob of the RA axis(*only on the manual non motorised mount). With the DEC tension knob loose, balance the scope tube by moving the scope along in the tube cradle rings, (loosen the cradle rings thumbscrews a touch, until the scope can be rotated and moved along the rings) until the balance point is reached. Tighten up the cradle rings. Tight enough to hold the scope firmly enough to prevent it slipping if the scope is pointed vertically, but loose enough to let you be able to rotate the scope round, so the eyepiece is in a comfortable position for the eye, at any point of a viewing session.

Tighten the tension knob again. Now slightly loosen it til the scope can be moved to and fro by hand. Not too loose. You should be able to use the large slo-mo knob to move the scope. If the tension knob is too loose, turning of the slo-mo knob won't move the scope(or it will move intermittently).

On the manual mount, the RA axis can be set up just like the DEC axis, above.

Regarding the manual mount - the RA slo-mo wheel should be ‘wound’ all the way back, so you can track an object for the full 7 degrees available travel.

The 1M(MT-1C) and 2M(MT-2C) motorised mounts need various tune ups in the RA axis as described below. It’s easier if you remove the housing backplate, to give easier access to the internals. *see note 2

Balancing on the RA axis.

With the mounts dec axis horizontal to the ground (the ota at this stage, can be vertical, horizontal or in between), look in the back of the mounts motor housing. At the back, on the clutch plate, you'll see three screws. Loosen them off a few turns. Now, because of the clutch, you’ll never be able to get the RA axis fully loose. Nothing we can do about that. You just need to estimate the balance by swinging the DEC arm/axis to and fro to determine the best balance. Move the weights up or down the shaft to suit. *see note 5

RA clutch adjustment.

The main large RA clutch needs to be tensioned correctly. This is achieved by tightening or loosening the 3 sprung screws *(see note 1) on the large clutch at the back of the main housing. With the DEC arm/axis horizontal, or close to horizontal to the ground, turn either one of the plastic RA thumbwheels and see if there is slippage. ie: when turning the wheels, the RA shaft doesn't move or does so intermittently. (If these wheels are very hard to turn, loosen the 3 screws on the small motor clutch/cog. Access is through the small side porthole.) You may be able to see this, a bit easier, by looking at the setting circles, when turning one of these wheels. Try this with the scope ota on both sides of the DEC arm (when looking from the rear). In effect you'll be trying to move either the scope or the countershaft weights up. This will help determine if the balance is correct. Again don't tighten them too much or it'll make scope movement, by hand , a bit too hard, or if the screws are really tight, impossible.

I’ve found over the course of a viewing session, the clutch can sometimes loosen off. So I always keep a screwdriver handy, to ever so slightly, tighten the screws again.

Setting the worm and gear meshing.

The steel worm and brass gear (both of which can be seen in the back of the housing) need to be meshed well too, otherwise you’ll feel a slight rocking movement when you grip the DEC arm and rock it to and fro. You’ll also notice it when moving one of the RA hand wheels. There will be noticeable play, or backlash, when reversing directions of the wheel. If it needs adjusting, do the following. Remove the left hand side plastic thumbwheel (opposite side to the switches) to gain access to the 4 small screws holding the worm bearing in place. Loosen them. Place a small screwdriver into the handwheel screw hole and whilst pulling up on the screwdriver, tighten the 4 small screws *see note 4. You don't want the meshing too tight or the worm and gear will not work correctly and not too loose or the rocking movement will not have been cured. On the 2M mount this backlash can be adjusted ‘til there’s virtually zero play. On the smaller mount, I’ve read that this backlash can only be improved upon. There may always be a slight amount of movement.

Motor clutch adjustment.

If the motor clutch is too tight, the RA hand wheels will not easily turn by hand(the motor will still move the RA axis, though). The clutch should be loose enough to enable the wheels to turn by hand, but tight enough for the motor to turn the RA assembly without slipping. The 3 screws, on this small clutch, adjust the tension. If you see the motor gear slipping then the 3 screws need tightening. Try 1/4 turns on each and then switch on the motor again. Do this till the slippage stops. Once again, too tight and the hand wheels will be hard to turn. Be aware that the RA handwheels are always going to be harder to turn than other types of mounts, due to the clutch system.To test, set the RA setting circles to 0 hours. Switch on the motor and come back in an hour. The setting circle scale should now read 1 hour. If less, then there has been some slippage. Tighten the 3 screws by a small amount, perhaps no more than a quarter turn and try the procedure again.

All the above is moot, if the motor clutch gear is not meshed well with the worms large gear wheel. There are 3 screws found underneath the housing, which let you adjust the motor clutch unit to suit *see note 3

Finally, for reasons unknown, the scale on the RA setting circles are labeled the wrong way round for northern hemisphere users. I used some small sticky labels to correct this.

Cheers,

Andy Howie

ps: I'm not the worlds best at getting what's in my head to the page, so if you think something can and should be changed, please say. Same goes if you reckon something is plain wrong. Ta.

pps: I'll get some pics up asap, which should help improve the explanations.

ppps: Tal rate the carrying capacity of their mounts as follows.

1/ small manual mount MT-1 = 7kg*

2/ smaller of the two motorised mounts, the MT-1C = 10kg*

3/ 2M mount, the MT-2C = 12kg*

4/ Newer Stepper mount, the MT-3S = 20kg

*After years of using the 2M mount, I must say that Tal have been remarkably conservative in the rating of it. I've found that mine, after tune up, can cope with up to 20kg of compact scope weight, which the newer Stepper mount is rated for. If the MT-2C/2M can’t hold as much as this model, I’ll eat my hat.

I would be surprised if the MT-1C couldn't cope with at least another 2kg also. I haven't tried, or used this mount though.

The manual mount works very well with the 4.5" newts and is adequate when carrying the 100RS.

Note 1 The springs used on the screws for the RA clutch plate can get badly mashed with use. I'd recommend sourcing some better quality beefier replacements(I used the following size = 1.5 x 8.5 x 12)

Note 2 To make access easier to the RA clutch and motor etc, think about holding the backplate on with one or more M3 thumbscrews, rather than the five small screws as standard. Makes adjusting the clutch far easier rather than trying to do it through the rear porthole.

Note 3 I find the provided slotted counter sunk screws, that secure the motor unit, to be a bit of a pain to get at with a screwdriver. I changed mine to ones that let you tighten them with an allen key. Far easier.

Note 4 The provided mild steel screws that hold the worm shaft and bearings in place can get very chewed up, so again I replaced mine with stainless versions. (I decided on allen headed c/sunk screws)

Note 5 When using a heavier scope than the one supplied with your Tal mount, it would be a good idea to source some extra counter weights.The Tal weight shaft is 19mm o/d, so there is only minimal slop, when using the more common weights that have a 20mm hole in.

[Komet]

This takes me back. My first serious scope was a TAL 2M. I think it was a Russian army 6" mortar originally it was so well built. I started out imaging on it also first with a plain old Toucam then a modded one all the way to a 2HS Atik until I was forced to upgrade as I wanted guiding.

I converted the mount to run from a 12v battery instead of the mains and made a handset for speed control for the motor. I also made an electric focuser for it.

I learnt an awful lot using that old beast from polar alignment all the way to basic imaging. Got some decent unguided images too.

I must admit I wouldn't mind another - just for looking through.

Anyone flogging one?

[AndyH]

Until I get the above rewritten, this link has a discussion and update with pics.

http://stargazerslounge.com/showthread.php?p=2311433#post2311433

Cheers,

Andy.