"Slippage" in my Synscan AZ GOTO

[RTamer]

I am the definition of "beginner", so bear with me.  I bought a Mak 127/1500 Skywatcher Black with Synscan AZ GOTO mount to start with.  When the scope is centered in the dovetail it shouldn't actually be able to move, if that is correct, but with little pressure I can move it.  Without the scope it is very difficult to move.  My beginners' questions are:

- Is this some kind of safety measure from Skywatcher so the motor isn't damaged?

- If this is wrong, is the scope too heavy for this mount?

- Is there an upgrade from the rubber wheels used to actual gears for the motor and drive wheel?

- If there is no upgrade, are there replacement parts for this system?

I really appreciate the help as I have never had something like this before and don't want to take it apart before I know what's up.  (I did remove the cover to see the setup).

[Owmuchonomy]

Welcome RTamer. Are you sure there is a problem?  The mount is designed to move your scope in Altitude and Azimuth using motor power from the internal drives.  Have you made sure the clutches are tightened fully before setting up the mount and telescope?

[RTamer]

Well, I'm not exactly sure.  This mount has no clutch to tighten.  I also have a Heritage 90 Virtuoso, but that mount has a clutch for each motor that I can adjust.  If something needs to be tightened, then it would have to be under the housing which I didn't see as I had it opened. 

[Owmuchonomy]

Somebody will be along soon who has more experience of that mount.

[RTamer]

Ok, thank you.

[ronin]

There will be a clutch somewhere and I would say that this is where the movement is from and it is - as best I know - normal. They are not meant to be solid.

Years ago Meade said "Tighten the clutches" so people TIGHTENED the clutch and the things burnt out the motors. Meade revised the instructions, but only after several mishaps. I think that Skywatcher managed to say tighten so the scope is firmly gripped but not too tight so people were not too heavy handed with those.

Unless the scope is slipping under it's own weight and movement then all is I think OK. And you being able to move it by hand would be expected. It just depends on how easy.

Concerning the weight and the mount, well unfortunately they tend to supply a mount that will just handle the scope. In the related Celestron scopes the 4SE and the 5SE share the same mount, so the 4SE is pretty solid whereas the 5SE is towards the top of the limit of the mount. I have no idea where the 127 mount fits in, however it could be at the upper limit as 127mm == 5". Just a guess but I suspect half correct.

Would have expected a set of clutches on it somewhere, seems strange not to be present.

[Cornelius Varley]

The older az goto mount doesn't have any clutches, unlike the newer version, but you must make sure that the mount is balanced fore and aft to ensure the load placed on  the alt drive gears is kept to a minimum. The mount uses gears, not rubber wheels, to drive it in alt and az directions and there are no upgrades available.

[Cosmic Geoff]

I've dismantled the essentially similar Celestron mount for inspection. There are gearboxes - no rubber wheels. There is a slip clutch for altitude which will slip if sufficient pressure is applied. It is there so that it will slip if the scope fitted collides with the mount. There appears to be no azimuth clutch.  The altitude clutch can be adjusted but unless it is slipping during observing, leave well alone.

The 127 Mak is the heaviest scope that can sensibly be used with this mount and tripod.

[RTamer]

@Cornelius - You are correct about the gears, they are metal.  This mount was purchased in 2015, I just bought it used.  It works fine, as far as I can tell and the bluetooth I just built works great.  I'm just worried about this slippage.  I don't know what the ratings are for this particular mount.  Here a couple of photos of what I received.

[RTamer]

@Cosmic Geoff - Yea, I see that also.  just wondering if the stepper to the transfer gear is belt driven now.  I'm not going to tighten, or loosen anything unless someone here says to. 

[jambouk]

You can gently tighten the nut under the dovetail to tighten the altitude axis, and there is another nut under a bar at the very bottom on the under surface of the mount head to tighten the azimuth azis. They should be snug and prevent you from easily moving the axis by hand, but not so tight that the motors struggle to move the axis.

[Cornelius Varley]

12 minutes ago, RTamer said:

@Cosmic Geoff - Yea, I see that also.  just wondering if the stepper to the transfer gear is belt driven now.  I'm not going to tighten, or loosen anything unless someone here says to. 

It is a box full of small gears.

[RTamer]

@Jambouk - ok, i'll give that a try, but isn't the axis supported by a bearing?  If so, I could tighten it until I'm blue and it won't make a difference.

 

[RTamer]

3 minutes ago, Cornelius Varley said:

It is a box full of small gears.

Ok, that doesn't make me feel better.  As long as it doesn't strip them.

[jambouk]

If the spanner keeps turning there is a more sinister problem; tightening these two nuts is a commonly undertaken procedure [and fix] for the axes in these mounts being a bit slack.

[RTamer]

Trying to think what I'm going to tell my wife when a new Synscan comes in the post after I mess this one up...  I'll give it a try.

[happy-kat]

Being worried about slippage and actually slipping are two different things.

In use is the telescope slipping from holding where it go to position?

Also unlike the Virtuoso this mount is not designed to have the telescope moved by hand, which for me might mean users don't usually try to move the telescope by hand so don't have a reference of what is normal movement if any.

Why did you try to move it by hand?

Just thinking there might not be a problem, if goto works and the telescope tracks fine, all is good.

[RTamer]

@Happy-kat

The first time it happened was only an accident when my elbow knocked against it and it changed it's position.  The power was off.

As soon as I would add power, there was no slippage.  Tracking was great.  When I attached my DSLR to it, it moved on it's own (of course because of the extra weight), with and without power, and that's when I decided it was about time to make my first post, as opposed to just lurking and reading.  I did tighten the nuts, as Jambouk said (only lightly, backed off 1/8 turn), and the Mak is solid (with and without power).  I don't hear any change in the motor, so I will assume that there is no drag on the system.  I'm going to attach my camera again and see what happens.

How can I find out the weight rating for my mount?  I don't see a model number.

[Cosmic Geoff]

You can shift the scope/camera assembly up the dovetail to balance it better. Also look out for the camera hitting the mount at maximum elevation (that's why there is a clutch ).  If you are going to use the camera a lot, consider setting a slew limit to stop it hitting the mount and killing the Goto alignment.

[RTamer]

11 minutes ago, Cosmic Geoff said:

If you are going to use the camera a lot, consider setting a slew limit to stop it hitting the mount and killing the Goto alignment.

Great piece of advice!  Just found that under the "Setup Functions" menu.

Does anyone know if Stellarium overrides all of the functions of the handset?  That would kind of ruin the idea of setting the elevation limit.

The camera is important in that, my son (6yrs) loves the stars and universe and I really want to see if this might be a field for him.  He could later use my 90mm Mak.

[Louis D]

2 hours ago, Cosmic Geoff said:

You can shift the scope/camera assembly up the dovetail to balance it better.

You could also add counter-balance weight to the front of the tube to counter the additional weight of the camera.  Rehab cuff weights might be an easy solution.  Just wrap one around the tube at the front.  As long as it's balanced, I think the mount should be able to handle the extra couple of pounds.

[kilix]

The mount is designed to have some slippage in Alt axis.
You did well to tighten the nut under dovetail, I did the same, but I tightened it only so much, that the scope is quite easy to move when I want it to. But it won't move accidentally or by itself, or when I attach a camera to it.

I move the scope manually before starting my observing session - I align the scope in alt axis by hand roughly to first alignment star. There is no slippage in AZ axis though, which is logical.

There are multiple myths, which one can read regarding this mount, like "never move the scope by hand." When you dissassemble the mechanism and you understand what you are looking at, then it is obvious that the alt axis is designed to have some slippage and there is no way you can damage anything when moving it by hand. Ofcourse, you can damage something when you overtighten the nut under the dovetail and then force the scope to move, those gears are obviously not designed to withstand 100Nm or so.

The Alt axis should be relatively easy to move when you want to move it, but should stay in place when you want it to stay in place. The slippage also helps, when the scope encounters limits of the alt axis and the scope actually pushes against the mount/tripod assembly. If there were no slippage, then those plastic gears in reduction gearbox would get stripped or the motor would burn out (I don't know if there is thermal protection on the motor). Also, this is why there is no slippage in AZ axis, when the scope moves in AZ axis, there is no possibility for it to run into the mount/tripod assembly, so no need for slippage.

[RTamer]

@Kilix - Thanks for the good information.  I did notice that the nut on the inside of the is spring loaded, and that would make perfect sense being able to adjust the amount of pressure two plates would apply to each other, or not to each other.  I'm not going to take it completely apart because now, with the help from everyone here, I am very satisfied with the way it works.  Just wish we had some clear skies in here in Germany so I could try it out.  Thanks again.