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PhotoGav

Moving Mesu Mystery

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I have a Mesu 200 mount on my pier. I like it. However, I occasionally find that it has decided to go slew-about between sessions. I just went to my obsy and found that the mount had moved all the way to the west in RA. Dec was as I had left it. The mount had been left turned off.

I turn off the mount between sessions, so if this is a powered action, it must be happening at start up. I put the mount back to its park position (which it appeared to have lost, so I have done a dodgy CdC rough sync and reset the Park position - it will need to be properly synced next time there are stars visible). I then turned it all off and did a power up and it all stayed exactly where I had left it, in the correct park position. I have now turned it off again and will see what happens.

Any ideas as to what could be causing this? I am fairly sure that I have it balanced properly, though that is quite hard to tell with this mount. Could it be ‘scope end heavy’ and it is slowly drifting when the motors aren’t powered up? Can’t believe that is the case and it doesn’t always happen, which surely it would always happen if it was an imbalance problem?

Help please! People keep on saying that the Mesu is ‘fire and forget’, but this is a major hiccup.

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When switched off it will definitely move if unbalanced..... I left my lens cap on once and that pulled the mount in a downwards trajectory.  You can lock it with the small push in clips on each axis if you need to.

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2 minutes ago, swag72 said:

When switched off it will definitely move if unbalanced..... I left my lens cap on once and that pulled the mount in a downwards trajectory.  You can lock it with the small push in clips on each axis if you need to.

Mmmm, OK, thank you Sara. So perhaps the culprit simply is that it is unbalanced? I guess the best solution is to balance it all better, followed by leaving it turned on? I don’t want to use the clips as I don’t want to have to go out to the observatory before every session. 

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I wouldn't  personally leave it turned on..... proper balance should sort it. How are you parking it? I have mine parked traditionally weights down pointing  towards Polaris so the balance is fairly forgiving there. Saying that my 'movement' was when I used to park it horizontally to allow the roof to close...... extra weight on the front end and it moved accordingly.

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20 minutes ago, swag72 said:

I wouldn't  personally leave it turned on..... proper balance should sort it. How are you parking it? I have mine parked traditionally weights down pointing  towards Polaris so the balance is fairly forgiving there. Saying that my 'movement' was when I used to park it horizontally to allow the roof to close...... extra weight on the front end and it moved accordingly.

I agree, best to not have to rely on leaving it turned on. I park in the missionary position too - weights down, pointing towards Polaris. I will go and move the counterweight down the shaft a bit and monitor the situation...

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15 minutes ago, xtreemchaos said:

Aliens 😉..

Gremlins, just the hoard of Gremlins who moved in the day the dome was delivered...! I can hear them chuckling now...!

  • Haha 3

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If you parked it with the counter weight down and the scope pointing to the NCP, I can’t see it moving from that location unless you have a LOT of ancillary kit attached to the scope in a lop sided fashion. 

Using the latches is ok but you have to be really disciplined in remembering to remove them before powering up the mount. They are very hard to unlatch if the mount has been running with them in the closed position, definitely not recommended.

Not much help, but I have powered up the Mesu from scratch many times, and it has never done a random slew. I always start Sitech.exe first, then switch on the mount, then connect to CDC.

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One of the robotic Mesus I host had the habit of moving when not asked to do so. I'll ask the owner if he can contribute any wisdom here. 

Olly

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6 minutes ago, tomato said:

If you parked it with the counter weight down and the scope pointing to the NCP, I can’t see it moving from that location unless you have a LOT of ancillary kit attached to the scope in a lop sided fashion. 

Using the latches is ok but you have to be really disciplined in remembering to remove them before powering up the mount. They are very hard to unlatch if the mount has been running with them in the closed position, definitely not recommended.

Not much help, but I have powered up the Mesu from scratch many times, and it has never done a random slew. I always start Sitech.exe first, then switch on the mount, then connect to CDC.

Thank you. Agreed, seems pretty unlikely. I’ve been out and had a look again. I really can’t see it being an imbalance thing as I put the scope to one side while the mount was powered off and it didn’t budge at all...

6 minutes ago, ollypenrice said:

One of the robotic Mesus I host had the habit of moving when not asked to do so. I'll ask the owner if he can contribute any wisdom here. 

Olly

Thank you Olly. I look forward to hearing more as this sounds exactly what I have going on. I hope the mount you host doesn’t misbehave anymore and you can supply an easy fix!

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39 minutes ago, PhotoGav said:

Thank you. Agreed, seems pretty unlikely. I’ve been out and had a look again. I really can’t see it being an imbalance thing as I put the scope to one side while the mount was powered off and it didn’t budge at all...

Thank you Olly. I look forward to hearing more as this sounds exactly what I have going on. I hope the mount you host doesn’t misbehave anymore and you can supply an easy fix!

I only host it and the problem is solved. I don't know the ins and outs of what was happening or what the solution was but the question is passed on. It had nothing to do with balance, however.

Olly

Edited by ollypenrice
Typo
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12 minutes ago, ollypenrice said:

I only host it and the problem is solved. I don't know the ins and outs of what was happening or what the solution was but the question is passed on. It had nothing to do with balance, however.

Olly

Perfect, thank you. I await the reply. 

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15 hours ago, PhotoGav said:

Perfect, thank you. I await the reply. 

My customer couldn't remember what his issue was but said, I can’t remember, but I think it had something to do with the encoder setting  in the sitech. It was losing its position so “Under horizon”  started to kick in. 

Something like that.

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35 minutes ago, ollypenrice said:

My customer couldn't remember what his issue was but said, I can’t remember, but I think it had something to do with the encoder setting  in the sitech. It was losing its position so “Under horizon”  started to kick in. 

Something like that.

Ok, thank you for asking...

I have found out something very interesting this morning... I powered up the mount and left it for about an hour and a half, no computer turned on or anything. I have just been to have a look at it and the pesky thing has moved... and has moved approximately 22°. So, this is definitely not a balance issue and is a powered movement. It appears to be tracking when powered up and not staying in its park position.

My next test is to put it back to the home position, power it up, connect up SiTech exe and leave it for a while. I am sure that it will be fine and stay put, but I will run the experiment and see. I will also look in the SiTech settings as there is bound to be something that is telling it to track on power up. As usual, issues caused by user error!!

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8 minutes ago, PhotoGav said:

 

Ok, thank you for asking...

I have found out something very interesting this morning... I powered up the mount and left it for about an hour and a half, no computer turned on or anything. I have just been to have a look at it and the pesky thing has moved... and has moved approximately 22°. So, this is definitely not a balance issue and is a powered movement. It appears to be tracking when powered up and not staying in its park position.

My next test is to put it back to the home position, power it up, connect up SiTech exe and leave it for a while. I am sure that it will be fine and stay put, but I will run the experiment and see. I will also look in the SiTech settings as there is bound to be something that is telling it to track on power up. As usual, issues caused by user error!!

Aha, if it's tracking rather than slewing then we've certainly had this here in the robotic shed. This is what Yves remembers of the issue. (The mount originally had a cigar lighter connection but we put a UPS in to power it instead of a direct transformer.) Maybe you need to check out  this business of the option not to track on power-up?

it was not slew but it was tracking that turned on after a power outage …
Marco really had slewing issues.
 
For me the UPS solved the unwanted tracking, the cigaret lighter plug was also not helping.
The option to not start tracking after power on is not being honoured well ...
 
Edited by ollypenrice
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Similar setting in the Meade that needed disabling otherwise as soon as powered up it would start tracking.

Dave :icon_santa:

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Yes, this is definitely the problem. It starts tracking on power up. I’ve just looked in the SiTech.exe Change Config! tabs and there is a tick box for ‘Track on Start’, however it is not ticked, so I would expect it not to track on start. The investigation continues. If somebody with a Mesu could please let me know if their ‘Track on Start’ box is ticked or not, that would be very interesting. 

I think that the easy remedy is to always connect to the mount with SiTech when the mount is powered up. It should be possible to stop it tracking on power up, but that might take a bit of fiddling!

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My Mesu was setup to track on start but as soon as I unticked the Track on Start checkbox in the SiTech config it stopped tracking on start.

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Good news, though yet to be fully tested, but surely this is the problem solved... In Servo Config, Equatorial Mode was ticked. This is an Auto Tracking mode that kicks in when the mount is turned on. I have unticked that mode and have left the mount powered on with no computer involvement. I’m very confident that this will fix the issue. Thank you all for your input and especially to Mrs Gnomus who shared Steve Richards’ advice in a PM conversation!!

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I have just checked the mount having left it powered up with no computer connected for over an hour and I am delighted to report that it hasn’t moved at all.

Case Closed!

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10 hours ago, PhotoGav said:

Thank you all for your input and especially to Mrs Gnomus who shared Steve Richards’ advice in a PM conversation!!

Sorry that you heard this 'second hand', Gav but I have been mega busy with family issues the last few days. Delighted to hear that it is all working well again and that it was a track and not a slew issue!

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2 hours ago, tomato said:

Good to hear, SGL is a wonderful thing.

Absolutely, those were the exact words I had in my mind as I exited the obsy following the successful final test!

29 minutes ago, steppenwolf said:

Sorry that you heard this 'second hand', Gav but I have been mega busy with family issues the last few days. Delighted to hear that it is all working well again and that it was a track and not a slew issue!

Please don’t be sorry! Even the Scope Doctor can’t be on call all the time!! I hope all is well in the family. It is a relief to have an ‘easy’ fix. No doubt there will be another issue along very soon... if the weather ever comes good to enable me to use the kit!

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The bard has a phrase for every occasion: all's well that ends well.

Olly

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