TAL2 mount

[jason.p]

Apologies for appearing a bit dull, but despite the excellent link from Andy in a previous thread, I am struggling a bit:(. I think the main problem is that I haven't really got a grasp of the different axes, DEC, RA polar (are there any others!). I've been reading as much as I can find and watching you-tube vids. Any other pointers would be appreciated.

One problem I have with my mount is that I can't lock the ?RA axis. The lever and big black knob don't lock tight enough. The lever comes up against the knob and housing before it will fully tighten and the knob alone won't hold it. I've included a couple of pics.

[AndyH]

Yeah this sometimes happens. Never fear, simple fix.

Loosen off the lever and look at the other side where the bolt/screw goes.

Remove this lock nut assembly. Now alter the lever bolt/stud, so that when it tightens on it, theres still space to go before it hits the wheel shaft. Probably turning the stud clockwise one flat should do the trick. Make sure you align the two flats or it'll be tricky to refit.

Hope that helps.

Andy.

[AndyH]

[jason.p]

Once again, many thanks Andy. Problem sorted. I also put a washer on the big wheel shaft which helps a bit. It's locked tight now.

(I now know the Dec and RA axis as well:)).

Progress indeed:icon_salut:

[AndyH]

You won't need to touch the lever again. When you want to loosen the mount to set it to your latitude, use the wheel.

[AndyH]

If you want me to do a run through of setting the mount out let me know? I'm more than happy to take some pictures of my mount and me setting the balances, meshing etc. I'm waiting for stuff to dry, so it wouldn't be a problem.

Andy.

[jason.p]

If you want me to do a run through of setting the mount out let me know? I'm more than happy to take some pictures of my mount and me setting the balances, meshing etc. I'm waiting for stuff to dry, so it wouldn't be a problem.

Andy.

That would be really helpful. As you probably realise this is all a bit bewildering at the moment and pictures make it so much easier to understand. I've no doubt I'll have many more questions and I really appreciate your patience and help.

[AndyH]

No problemo. Bear with me as I've got a second coat of paint on some stuff and then I'll post some pics up. Won't be too long.

Andy.

[AndyH]

Righto. Here we go.

Hopefully these pics will help http://stargazerslounge.com/showthread.php?t=156715 make more sense.

Part 1 - Balance the tube in the DEC axis.

Make sure the scope is fully loaded with finder and an eyepiece in the focuser.

1/ Set the DEC axis horizontal to the ground.

2/ Set the latitude to about 10 degrees

3/ Set the scope horizontally and tighten up the DEC lock/tension thumbscrew.

4/ Lock up the RA clutch by tightening the 3 screws(see next pic)

5/ Fully loosen the DEC tension thumbscrew and push the scope to and fro to test the balance.

6/ Move the scope along the tube rings until balance is reached. Point the scope close to vertical and test the balance at that position also. It may need adjusting slightly.

Part 2 - Balance the scope in the RA axis.

Loosen off the 3 screws on the RA clutch plate as shown in the above pic.

Balancing is the same principal as was done with the DEC. Move the weight along the shaft until balance is reached.

I'll continue this tomorrow morning as I'm going to have to recharge my cameras batteries.

Let me know if the pics help with the guide I posted above?

Cheers,

Andy.

[jason.p]

Thanks Andy, pictures really helpful. I had gone through the link you sent in a previous post about tuning the mount, but with the pictures it makes a lot more sense. I haven't had a chance to put any of it into practice yet but as soon as I do I'll let you know how I get on. I look forward to the next installment, and once again, many thanks.

[AndyH]

Hi.

Part 3

Fully tighten the x3 RA clutch screws. Move the motor/gearbox/cog unit back off the worm cog, towards you. x3 screws, holding the unit, can be found under the housing. Don't remove, just loosen.

Set the meshing of worm and brass gear as descibed in the guide. To check grab hold of the scope and counterweight bar and try to rock it around the RA axis. If there's any slight movement/knocking you may feel it as well as see it if you keep an eye on the RA setting circle when doing this. If there is movement, the meshing is too loose. I described the fix in the guide.

I describe the 'small screwdriver' technique. There is another, less gentile method if the meshing is only very slightly off(I actually often do this when tiny tweaks are needed, over the course of months of use). With the plastic handwheel off, tap the exposed steel worm shaft up. Go easy, you don't want to do damage. Perhaps ever so slightly loosen the x4 screws holding the worm shaft bearings in place. Once you're pleased with the meshing(remember you don't want it too tight or it'll cause problems with the motor and it's clutch later), check both sides worm bearing screws for tightness.

Part 4

Setting the RA clutch - As described in the guide, plus......Loosen the x3 RA clutch screws by just enough to let you move the scope around on the RA axis by hand. Ignore the bit I wrote about the motor clutch as you've already moved it back, out the way.

Once all this is done, your scope and mount are ready to go, If you tighten the screws holding the motor unit(still backed off the worm shaft cog), you can use the scope and mount as is, manually, with no motor. I've done this on occasion when I've been away from the house and have forgotton to bring a power supply.......duh !

Next part I'll describe how to check the motor gearbox and the setting up of it's clutch.

Cheers,

Andy.

Edited May 21, 2012 by AndyH

[callump]

Thanks for this really useful thread Andy. I've just been resurrecting my old tal2 mount which has been rusting away in the lean-to... and it needs a few adjustements.

Cheers, Callum

[jason.p]

Another great set of useful pics. Thanks Andy. I'll set aside a few hours later in the week to have a go.

[AndyH]

Part 4

I've decided to rewrite the 'Motor Clutch Adjustment' in the guide.

The Motor & it's Clutch

Overview - The small motor driven cogged clutch is there to protect the motor, but more importantly, the reduction gearbox attached to it.

If the motor clutch is too tight, the RA wheels will not easily turn by hand, although the motor will still move the RA axis. I reckon it's not good practice, having the mount running this way, as there's the potential to put undue strain on the reduction gearbox, especially if the mount hasn't been fully adjusted.

The clutch should be loose enough to let the wheels turn by hand, yet tight enough to turn the RA assembly without it slipping. The 3 sprung screws adjust the clutch tension.

If you've just acquired a Tal motorised mount or it's not been checked in some time, I'd recommend doing the following, before any motor clutch adjustments.

*Note: Some older models use a plastic reduction gearbox. I’ve not had a good look at a mount with one on, but hopefully, the following is still valid, as regards how it and the motor are attached to the mounts housing.

To get a good look at the tiny gears in the reduction gearbox, remove it the from the motor. They’re screwed together. You’ll probably need to have the motor unit off the base of the mounts housing and in your hand. Be careful not to damage the power wires when doing so. Look for damage or wear on the gears and for excessive play in the gears shafts. Take a good look at the final gear, the one whose shaft drives the clutch. This is the one that usually takes the brunt of any punishment. As a test, try turning one of the earlier gears with a finger to run the gearbox through a full revolution.

Replacement gearbox/motor units are available from the factory in Novosibirsk, if necessary.

If all seems okay, refit the gearbox and motor. Fit the unit back inside the housing.

Fully tighten then loosen the x3 motor clutch screws by two turns. Push the motor unit up towards the worm shafts gear/cog until you get a good mate/fit between the two. Holding the unit with one hand, use the other to turn the RA hand wheel to and fro. Feel for a good fit. Also check that they are in line with each other. Keeping the unit in place, tighten up the 3 screws under the housing. Once done, turn the RA wheel to make sure the gears are still a good fit/meshing well.

Now connect the transformer and turn on the motor. You’ll see the motor clutch slipping. If you put some scores around the clutch(see 1st pic), it'll make seeing this far easier. Tighten by 1/4 a turn on each screw and check again. Continue until there's no sign of any slippage.

Be aware that the RA handwheels are always going to be harder to turn than other types of mounts, because of this 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 have moved on 1 hour. If less, then there has been some slippage. Tighten the 3 screws by a small amount and try the procedure again.

Your Tal mount should be all set up and ready to use now. You’ll probably not need to adjust the motor clutch for a long time, but be aware that the RA clutch might need adjusting now and again(perhaps even mid viewing session).

Hope this has been of some help.

Andy.

[jason.p]

More good stuff. Thanks Andy. And there was me thinking I'd just bought a telescope! There's so much more to it than I imagined. I don't think I'd ever have figured it out without your guide. Apart from anything else going through all of this is the best way to get to know your equipment.

(Think I'll be cheeky and ask if you'll do one on collimation and polar alignment next:D)

[AndyH]

Polar alignment is pretty simple, especially if you just want reasonable accuracy for visual use of your scope. I'll get back to you with details.

There are quite a few excellent collimation guides about. The 2M is very easy to collimate. Just need a bit of patience first time out. I'll put a post up for a simple explanation of how to do the 2M.

But I want something in return ;-)

Your scope looks like an old one. Any idea of the age? I'd love to see some more pics. Esp of the reduction gearbox area(is yours plastic?), the focuser and the eyepieces, if you got any with the scope?

Cheers,

Andy.

[jason.p]

I'll get as much info as I can. It's the very least I can do! There's component lists inside the packing cases, I'll get pics of them if it will help put an age to it. When I strip down to the motor/clutch etc I'll get pics, and of focuser and eyepieces filters etc.

Thanks again

Jason

[AndyH]

Hi.

A cheap n cheerful way to collimate your Tal newt is as follows.

Get a hold of a 35mm film canister. Cut off the bottom and put a very small hole in the middle of the cap. I heated up a pin over the gas stove and it went through the lid easily.

Insert the canister into the focuser, which should be racked in, as long as you can see all of the secondary mirror. If not, rack it out a bit.

1/ orange arrows - Centering the secondary mirror in relation to the focuser drawtube. Outer arrows point to the end of the focuser drawtube. Inner arrows to the very outer edge of the secondary mirror. You want to see an concentric gap all the way round.

2/ green arrows- Centering the reflection of the primary mirror in the secondary mirror. Outer arrows point to the very outer edge of the secondary mirror. Inner arrows to the inside ends of the tube(normally you're wanting to look for the edge of the mirror, but with the tight tolerances of the tube and mirror cell, this way might be easier to judge). Again, you're looking for a concentric reflection of the sides of the tube interior/centering the primary mirror.

3/ blue arrows - Centring the spider/secondary mirror in the reflection of the primary mirror. Easier if you look for the machined tabs where the spiders flat arms connect to the tube.

Pic taken through the pinhole of the canister of my Tal 2M

To be honest you can do parts 1 + 2 at the same time.

Loosen(anticlockwise) the centre sprung screw in the front of the spider secondary holder. This has the effect of moving the secondary unit further into the tube. The spring takes up the slack however and in effect, pulls the unit back onto the x3 tilting screws. If you (carefully, perhaps with latex gloves to prevent any finger prints being left on the mirror) grab a hold of the secondary body and you should be able to move it about. If not loosen the x3 screws. This will give you an idea of what to do. With a mixture of altering the centre screw, twisting the secondary about it's axis and the adjustment of the x3 tilting screws try to get the image concentric. Once done, carefully tighten the centre screw. Re-check and adjust the x3 screws if necessary and make sure they're snug against the secondary body. May take you a bit of time if it's way off. Be patient. You WILL get there.

Part 3 Primary mirror adjustment is done by loosening the mirror cells centre lock screw and with small adjustments of the sprung knurled knobs. It is far easier and quicker, if you can get someone else to do this, as you look through the canister and give instructions. If not, it'll take a bit longer. You might have to rack out the focuser to take the focuser drawtube out of the way. Look to get all 4 tabs as equal as possible. When done, snug up the centre lock knob.

Pics from left to right - 2M primary cell, secondary, Tal 1 secondary(side on showing the sprung centre screw and x3 tilt adjusting screws. Don't have a pic of the 2M. Same idea though)

Your scope should be roughly collimated.

Final fine tuning should be done under the stars at medium to high magnification. It only involves tweeking the primary cell knobs so that you get a nice concentric ring pattern of a slightly defocused bright star.

The 2M is classified as moderately 'slow', which means it is very tolerant of slight errors in mirror alignment. ie: It's easier to get right. It also holds it's collimation well thanks to the excellent design and build of the spider assembly and primary cell.

This may be of use - http://stargazerslounge.com/showthread.php?t=143960&highlight=Tal+focuser+rebuild

There's also various threads kicking about, here on SGL, regarding blackening some parts of the scope. Older Tals have some areas that could do with improvement.

I'll post up details of polar alignment tomorrow.

Andy.

Edited May 23, 2012 by AndyH

[AndyH]

Whilst I haven't used one, a lot of folk swear by a 'cheshire collimating eyepiece' for newts. Available for around £30. eg: site sponsor FLO sell a couple.

I didn't mention in the above post, that if not already done, it would be a good idea to centre spot the primary and perhaps put a small paper ring surrounding it(one of those punched hole protectors you get for ring binders).

Here's an in depth look at collimation - http://w1.411.telia.com/~u41105032/kolli/kolli.html

[AndyH]

Tut, tut.

Forgot to mention Astro_Baby's collimation guide. Excellent resource.

http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm

Andy.

[AndyH]

Before I talk about polar alignment, I forgot to mention this ealier.

When you have set the balance of the scope on the RA axis, using a marker pen, score a line where the weight should sit. Makes set up quicker, if you break down the 2M for storage.

Polar alignment of the 2M can done, roughly, before it gets dark, if you wish.

Before you put the rings, scope and the counterweight on the mount, with the pedestal sat on as level a ground as possible, set the latitude to zero. Position the DEC axis vertically. Position the top/mounting plate(where the rings attach) so that is in line with the RA axis. Now check with a spirit level to make sure it's level. Set the RA setting circle to '0' hrs.

Now turn the mount on it's RA axis until it's at '6' or '18' hours and the DEC axis is now horizontal to the ground. Put the spirit on the edge of the top/mounting plate, get it level and lock the DEC tension/lock knob.

Turn the RA axis back around to '0'. The mounting plate will now be in line with the RA axis. Fit the rings, scope and counterweight onto the mount. Re-set the latitude corresponding to your coordinates. Loosen the x3 thumbscrews that lock the mount into the pedestal and turn the mount until the RA axis(and now the top/mounting plate) is pointing north.

This will give a rough polar alignment.

When it gets dark enough to see polaris, using the edge of the top/mounting plate, sight along it. If it's not pointing pretty darn close to polaris, then adjust the latitude and/or turn the mount on the pedestal to suit.

This should be as accurate as you'll need for a visual observing session.

In case anyone reading this hasn't got their's, I've attached the original 2M manual and the modern one in a pdf file. The latter, whilst far better written, does not include info of the 2M mount(known as the MT-2C). But it explains general info about the use of Tal's scopes and in particular, the MT-1C, which is the lighter motorised version of the 2M's mount. So info relating to that, can be used for it's bigger brother.

Cheers,

Andy.

TAL1,1M,2,150P,150P8.pdf

tal-2.pdf

Edited May 24, 2012 by AndyH

[jason.p]

Thanks yet again for some great info Andy. I've got some time this weekend so I'll be on it!

Here's some pics of my TAL2

These are the parts lists inside the packing boxes

Here's the focusser

And these are the eye pieces and filters etc. There's also a thingy with cross-hairs.

(I'll get some pics of clutch and motor in the next few days.)

I don't know if this will help date it. I don't know it's history but I imagine it's an early one.

Thanks again for guides

Jason

[AndyH]

Hi.

Great pics. A very striking blue !!

I reckon possibly an early to mid 90's scope, going by the focuser, mount and eyepieces.

I'd move the knurled thumbscrews that hold the rings to the mount. A bit precarious in that position you have them! Move so they're holding the rings from below the mounting top plate.

Cheers,

Andy.

ps: the crosshair piece is a reticle and is meant to be screwed into the barrel of the 25mm plossl.

Edited May 24, 2012 by AndyH

[RichardL]

Brilliant thread! When I get time I'll read it properly. Jason, your scope is precisely the same as mine - identical eyepiece set, filters, the lot. First light for me was May 1996. Bought it from SCS Astro. In fact, before I bought it I visited the chap who (I presume) ran SCS to have a look at one - he had it set up in a small observatory on his farm in deepest Somerset. (We were introduced to his splendid pigs!)

For polar alignment I bought from SCS a sighting tube that sits on top of the mount. It's just an aluminium tube about 25cm long and 1.5cm across fixed to an angle plate so it can be positioned correctly on top of the mount. The latitude scale is off by about 2 degrees by my reckoning.

[jason.p]

Andy. I see you spotted my deliberate mistake:o:o. Thanks

Richard. Thanks for tip about polar alignment gizmo.