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Mesu mark 2 RA drift update


Jaspal Chadha
 

Hi all,

Lucas and I had another pop at problem solving the mark 2 mount before I finally send it off back to him ( it’s a hassle to send something this big off especially post Brexit ) 

Lucas noticed strange noise coming out from the R.A when slewing around the sky. To be honest I thought the mount sounded like this since day one. 

Under guidance I removed the metal casing down which is held with two grub screws. 



The main screw which holds the motor was loose ( not sure how this unscrewed itself )

With some marking I carefully moved the motor down and tighten into place and sounds much better.

The mount now sounds like as shown in Jose’s video https://youtu.be/DQp4fJnnY_Y


I’ll also on the next clear night using N.I.N.A ( thanks Gary Neilson ) for showing me the ropes on this one.

Crossing my fingers and feet that the issue has been resolved.  


Jas 





Kind Regards 


T. van Hees
 

I wish you much luck Jaspal. I had a rather strange sounding RA drive, too, and thought it normal because it was this way from day one. The mount came back from service better sounding but not better performing. Mr. Mesu keeps claiming it can not be the mount at fault (for irregular RA drift. No explanation as to where he thinks the fault lies instead).There are others with like problems. I fear it is a systematic problem with the Mk2 mounts that the manufacturer is trying to bury by stubbornness.

Sorry to the rest of the mailing list. I am quite convinced this is not a problem of the Sitech Controller/Motors/Software but of the implementation in the Mesu mount.


paul K
 

There's no need for apologies Torben, it's a protracted problem. If the mount is not at fault, then it's an electronics/ software fault, BUT it isn't a software/ electronics fault because the wider evidence of usage of Siderial Technology's products shows no problems of this nature.

When I bought my MESU mount from a U.K. dealer in 2015 I purchased the mount with controller and software. If it turned out to be not fit for purpose, I would be speaking with the dealer from whom I'd purchased with a statement to the effect of "it doesn't work, therefore not fit for purpose". The dealer can't palm the purchaser off by playing the hardware off against the software - it was bought as a unit.

So, if the dealer also happens to be the mount manufacturer and does not think the mount is at fault, imo it is their responsibility to provide a working system.

You can tell that as well as not being an engineer or electronics expert, I'm not a lawyer either :)

I hope you get a resolution.
best wishes
Paul


Jose Ignacio Sanchez Rodriguez
 

Hello Torben,

As others have said there is no reason to apologise. I think this is the right place to air these sort of concerns. In my case your thread has helped me a lot when thinking about my issue.

One thing that I am not sure if you tried, maybe you have, is to use the same rig on a different mount. If the discussion is wether the problem is on the mount or on the imaging rig, if you can make the same rig work on a different mount then the discussion should be almost settled. The only lingering issue would be on balance, as a friction drive mount can slip if not properly balanced. But that should be easy to settle by recording the mount balancing exercise. 

Best Regards,

Jose


Roland
 

Guys,

For what it’s waorth, apart from my own systems which use SiTech, I know of at least one other system that uses SiTech on a smaller Bellincioni mount which performs flawlessly.

There is always a bit of setting up to do but, since I use a separate observatory control system, once this is done SiTech becomes absolutely transparent. Last year during the peak of COVID, I worked for 6 months remotely without a hitch. 

I can’t make a comment about the Mesu mounts but I think you can rest easy with the accuracy and reliability of the SiTech system. 

Roland. 

On 17 Feb 2021, at 10:50, Jose Ignacio Sanchez Rodriguez <jsanchez.es@...> wrote:

Hello Torben,

As others have said there is no reason to apologise. I think this is the right place to air these sort of concerns. In my case your thread has helped me a lot when thinking about my issue.

One thing that I am not sure if you tried, maybe you have, is to use the same rig on a different mount. If the discussion is wether the problem is on the mount or on the imaging rig, if you can make the same rig work on a different mount then the discussion should be almost settled. The only lingering issue would be on balance, as a friction drive mount can slip if not properly balanced. But that should be easy to settle by recording the mount balancing exercise. 

Best Regards,

Jose


Jonk
 

I agree about balance - you need to balance DEC in all possible directions first, otherwise RA will not be in balance in certain parts of the sky you're pointing at.

An easy way to do this is place your entire imaging rig on a metal rod, or broomstick on a bench. You should be able to find the centre point of your rig by moving the whole thing 360 degrees around the rod / broom handle.

Move scopes back and forth and add weights if necessary (especially if you have L-R balance and cannot move the scope L-R).

One you've found balance in all possible directions, reinstall onto the mount with the centre of balance in the centre of the DEC and it should be fine.

Then you can set the RA balance. This may help with reducing slippage.


gary neilson
 

Hi All,

Its concerning to read all of these RA problems with the Mesu Mk2. I have the mount (received October last year.) and haven't had any of the issues fortunately.

It makes me wonder if the new clutch system of the Mk2 is part of the issue? As motor spacing is critical, I always make sure the lever is pressed firmly to lock the motor in place. Similarly for the axis clutches as any additional friction would mess things up. 

Other steps I've taken include:

  • Acceleration. Reducing the acceleration parameter in servo config by half which is probably very conservative. This prevents possible slip at the beginning or end of a slew.
  • Balance. Ensuring its balanced in RA/DEC off the mount. I address any off-axis loads that would exceed the torque spec of 10NM (even though it appears balanced when the CW bar is vertical or horizontal). As an added check I've found if I run guiding assistant in PHD2 and I see any backlash, its likely some minor slippage is occurring - I tend to ignore this if its small and do not compensate for it in PHD2 settings. Repeating the calibration and measurement in a different part of the sky clears it so certain angles do have an impact it appears. 
I used to use the dowel method described by Jonk. But now use an old Wii balance board (luckily its survived our  last move!) and software I found for a project at the University of Colorado. Its much safer as I simply place the scope/accessories on the board and adjust until the COG is centred in the reticle! No more wobbling of heavy equipment while finding the fulcrum!

Cheers

Gary.


Don W
 

Hi Jonk and all,

Balance in DEC must be done in two orientations:  Horizontal scope and vertical scope.  This is especially true when there is ANY non-symmetrical installation of scopes or multiple scopes, guide scopes, or cameras.  It is true that balance in Dec should be done before balancing RA.

Don W