need some mechanical help (scope problem)

[claire1985]

I need some advice from someone who is mechanically minded, my nexstar isn't working properly, the motor will turn the scope left to right no problem but up and down doesn't work properly or sometime needs a helping hand to get moving,

is it possible to change the motor? I've not opened it up yet to see how the thing works, I'm waiting for some advice first,

[leelee970]

a number of questions -

1   how old is the mount? or more important how often is it used?

2   what supply are you using - batteries or mains?

3   does it move without scope attatched?

4 (I'm not too familiar with your mount - although I have one stored away) is everthing tightened up, and is there anything loose inside?

[Davey-T]

Would check power supply first, I have a Nexstar and it's very finicky about having full voltage available for slewing.

If using batteries a single dodgy battery or coroded terminal will stuff it

Dave

[leelee970]

Dave, my thoughts too.

check supply voltage, connector (and clean) etc.

If it moves once push started it sounds like a voltage problem.

[claire1985]

It's being stored at a friends at the moment, every time I've used it it's had batteries in,

I have a 12v battery but need to buy a lead to use with it so I've never tried it out,

as for the age ect it wasn't mine from new so I really have no idea,

I'll check the power issue first, luckily i have a good friend who is an electrical engineer so I'l get her to have a look for me and test the power outage.

[Dude_with_the_tube]

if this is happening only when you have a relatively heavy eye piece in,then for sure its the clutches what are slipping.they need adjusting.i dont think its the motor issue unless it is not moving at all.

[claire1985]

how easily is it to check these things? are they easy to open up and have a look? I wish it was here now so I could have a mess.

if this is happening only when you have a relatively heavy eye piece in,then for sure its the clutches what are slipping.they need adjusting.i dont think its the motor issue unless it is not moving at all.

[leelee970]

you'd be better of using a mains powersupply. they really are not very expensive. Maplins will have something.

try it with known new batteries.

My Nexstar mount was much better once i moved away from batteries.

[Dude_with_the_tube]

how easily is it to check these things? are they easy to open up and have a look? I wish it was here now so I could have a mess.

relatively easy to check if it is clutch.Put a heavy eye piece in and try slewing the scope up and down,if you can hear the motors running but tube is not slewing or you have to push up/down the scope with your hand(what you call help) and then the motors kick in and carry on slewing the scope it is deffo clutches.

I dont have a nexstar system as such i can not comment how difficult or easy it is to adjust clutches,but on skywatcher it wasnt a rocket science.there should be a central shaft(threaded bolt) holding whole assembly with a nut what tightens the whole thing down.this is the one you need to tighten up.Adjust by a quoter turns and test,if still not sufficient adjust more.Dont over do it as this might burn the motors.

there might be a topic somewhere on internet how to adjust clutch on nexstar system or alternatively folks here who has one and have done it should be able to help.

[claire1985]

relatively easy to check if it is clutch.Put a heavy eye piece in and try slewing the scope up and down,if you can hear the motors running but tube is not slewing or you have to push up/down the scope with your hand(what you call help) and then the motors kick in and carry on slewing the scope it is deffo clutches.

I dont have a nexstar system as such i can not comment how difficult or easy it is to adjust clutches,but on skywatcher it wasnt a rocket science.there should be a central shaft(threaded bolt) holding whole assembly with a nut what tightens the whole thing down.this is the one you need to tighten up.Adjust by a quoter turns and test,if still not sufficient adjust more.Dont over do it as this might burn the motors.

there might be a topic somewhere on internet how to adjust clutch on nexstar system or alternatively folks here who has one and have done it should be able to help.

thank you! as soon as I have the scope back I'll give it a once over, I'll also get a lead to connect my battery up when I'm next out in birmingham.

[faulksy]

hi claire, as said possibly the clutch, does it sound like the motors are driving though ? it could be the brass pinion gear if it has be overloaded/not balanced. shouldnt cost much if its that, if its the clutch it might be adjustable

[Peter Drew]

Claire. I've just had a look at my 8SE mount, where the handset clips on to the fork arm there is a cover secured by 3 Phillips type screws, removal of this plate reveals a large nut for adjusting the clutch tension. My setting is not particularly stiff so good balance is important, a good power supply is also essential. Good luck. 

[knobby]

Hi Claire,

found this on another forum... Had the same issue on my old 4se.

Sounds like your altitude clutch is slipping... a common thing with the SE telescopes. The process on the 4/5SE mount is simple. I've never done it with an 8SE mount but the process should be very similar. Be aware, there is a very dangerous process described on some of the forums for adjusting the altitude clutch.

The altitude axis bolt ( actually a threaded rod not a bolt) has two retaining nuts (self-locking aircraft nuts). One of the two nuts is for adjusting the altitude clutch pressure and the other nut is for adjusting the play and freedom of movement by the drive motor in the altitude axis. If you tighten the clutch adjustment nut too much, you lock up the clutch and no longer have protection from a tube strike. If you tighten up the nut for adjusting the play in the altitude axis, you freeze the drive gearing in place and can burnout or destroy your drive motor.

How do you tell which nut is which. Celestron made it difficult to get to the nut for adjusting the play in the altitude axis. To get to it, you have to remove your hand controller then remove a plastic motor cover. The altitude axis does not use roller bearings but a nylon thrust washer for a bearing. When you tighten on this nut you are adding pressure to the thrust bearing. This will increase resistance to movement and stop slippage in the altitude. However, it also increases resistance to any movement including movement by the drive motor. Tighten this nut too much and the scope will not rotate in altitude and you will destroy your drive motor. Tighten somewhat too much and the slippage you are experiencing will stop but your drive motor will be laboring under a heavy load...and can burn out.

On the other hand, to access the clutch nut, all you need do is remove the bolt that you tighten to secure your telescope to the mount and you have direct access to the clutch nut. Manually take your hand and move the saddle where you attach your telescope and feel the resistance. At the moment it is probably not that much. Tighten the nut until a firm twist is needed to move the saddle. Put back the bolt that secures your telescope and you are finished.... no need to open up your mount for a simple procedure. If you over tighten the clutch nut, then you will not have as much protection in case of a tube strike but you can not restrict or freeze movement by the drive motor.

Thread is here

http://www.astronomyforum.net/astronomy-beginners-forum/130812-celestron-nexstar-8se-potential-problem.html

Good luck

[ronl]

You would be better with one of these

http://www.harrisontelescopes.co.uk/acatalog/Celestron_-_SkyWatcher_Compatible_12v_Mains_Power_Supply.html#aPSU

or this http://www.firstlightoptics.com/astronomy-cables-leads-accessories/skytron-power-supply-cable-with-ring-tongues.html

[leelee970]

or something like this

http://www.maplin.co.uk/p/maplin-20w-switched-mode-acdc-multi-voltage-power-supply-vn10l