Hello, and: Mesu 200 Mk2, Sitech, Tracking Problems

[Staring]

Hello, I am Torben, from Germany. I found quite a few posts here regarding the Mesu mounts, some of which convinced me to purchase one as a step to using larger scopes. Unfortunately, I have a problem with tracking: If I slew to a target near the celestial equator, RA tracking stops after a few seconds. Sitech.exe will report the scope status as tracking and RA/DEC coordinates stay constant. I can only resume tracking by slewing to a different target.I am using Voyager for imaging control, but I could isolate the problem, and it occurs without Voyager, too. Sitech version is 0.94N from the Sitech web site.

Does anyone have an idea what the cause could be?

[steppenwolf]

Welcome to SGL, Torben. I too have a Mesu 200 which performs perfectly. I wonder if you have a horizon limit set too high in either SiTech or your planetarium software although in fairness, I would expect SiTech to report 'Stopped'. Worth a quick look and also worth contacting Lucas Mesu directly as he is very responsive and helpful.

[Staring]

Thank you for your quick reply.

 

I have not touched the horizon limits yet, but had cleared the horizon file just to be sure, and the problem remained. I have also contacted Lucas, who gave me some config files. These helped with some slewing/alignment problems I had but did not resolve the tracking issues. I am in touch with him, but wanted to tap into the knowledge of the userbase, too. With the abysmal weather here, the testing proceeds rather sluggishly (2h of clear sky in 2 weeks).

[andrew s]

How well balanced is the mount? Regards Andrew 

[steppenwolf]

14 minutes ago, Staring said:

With the abysmal weather here, the testing proceeds rather sluggishly (2h of clear sky in 2 weeks).

Luckily, you can still test without a clear sky as you don't actually need to see the test object that you want to track. It is a little perplexing that you are getting a stopped mount without a stopped message. Slightly off the wall question but does the mount 'know' for certain what side of the meridian it is on?

[Staring]

Thanks again for helping out. I have balanced with great care. Sitech.exe does not show “pier side”, but I think if there was a problem, slewing would be impaired and tracking in other parts of the sky, too (which works fine).

I am quite sure it is a problem with my mount settings. I can hear the RA Motor stop when the problem occurs (a bit difficult because the computer is quite loud,  it I am sure). Slewing away from equator makes everything work again. Turning off and on and disconnecting etc. does not. 

With “non-clear skies” what I really meant was basically continuous rain for the last two weeks. I probably should just move the mount indoors and test there.

[steppenwolf]

15 minutes ago, Staring said:

I probably should just move the mount indoors and test there.

I've done that before now!!

[Staring]

Indoor space where a running mount does not lead to marital arguments  is heavily constrained (well... used up...). I might have to disassemble a part of the music studio, which is a hassle to cable up again. The mount/scope lives under a telegizmos 365 cover with dew heater. Everything keeps nice and dry there, always.

I actually expected the mount to perform from the set-up and not having to start out with lengthy trouble-shooting. I probably should have known better, in this game. I spent more than 10 hours so far (8h and 2h of clear sky) trying to fix various configuration problems. I find the Sitech software incredibly opaque. Before buying, I thought I understood the software. I do not. At all. Most settings are either not needed for the mount, or do not do what I think they do. There is no online help in the software and the manual is a difficult read. The QuickStart from Lucas Mesu was quick and easy to follow. Just, did not work for me.

Currently I am using factory settings from Lucas Mesu, just adjusted the location. He is very helpful and approachable. No luck, though. 

[Skipper Billy]

Have you set a 'Park' position??  I found that when trying to slew past the meridian before a park position was set resulted in it coming to a halt in an odd place as the mount thought the meridian was in a completely different place until I had told it where it actually was - ie at the park position.

 

[tomato]

Questions on the Sitech forum are usually answered promptly by the folks at Sidereal Technology, although they have been through some traumatic times recently with the Oregon wildfires.

It’s definitely worth posting a query on there.

[Staring]

Thank you, again. On the sitech group, someone had the same problem and fixed it by reinstalling the software. I tried reinstalling before. I have now uninstalled and upgraded to a higher version that I found in that forum. I can no longer reproduce the stop of the RA motor. So, next check will be under the stars. If they ever come out again.

Edited October 8, 2020 by Staring

[Staring]

Thanks again for the help, everyone. I have some unexpected clear skies tonight. After upgrading and reinstalling the Sitech software I now have no more tracking issues. Guiding is at 0.35" RMS, which seems excellent with (for here) mediocre seeing of about 2" FWHM, and there is still room for improvement of focus on the OAG.

[Laurin Dave]

Pleased it’s fixed..  that rms is pretty typical for a Mesu 

[tomato]

Good to hear, I was getting 0.45” rms on my Mk 1 last night but all the RA corrections were in the same direction. I suspect my ~100kg total all up load needs a bit more balancing.

[Staring]

Thanks for trying to help, again. Unfortunately this did not turn out well after all. I thought to post here because reports on this forum were instrumental in me deciding for this mount.

I got the mount end of September, with „first light“ in Oct 1st. In addition to some problems configuring the Sitech software (which I am now very confident in, it is not so bad once you get to know it), I had the above mentioned troubles with intermittent drift and stopped tracking in RA. The „good hour“ unfortunately was a singular experience. In addition I soon got „Motors in Blinky“ errors in the Sitech software which needed a restart of the mount to resolve.

Mr Mesu kept being very responsive but he demanded more and more tests from me. All these seemed to serve the purpose of proving it was not the mount at fault. I lost patience after four weeks and demanded of him to take the mount back for service. I had to pay 140€ of postage to ship back everything except for the counterweight shaft and the bent-knee pier.

He diagnosed a faulty DEC encoder which was fixed and adjusted torque on the RA axis. There was a huge stretch of bad weather here for several months which delayed my testing.

The “Blinky” problem was solved with replacement of the DEC encoder. Unfortunately the RA drift is still bad (between 2.5-14”/minute). In addition the hand controller causes random slews now. There are other people with similar unresolved issues.

Considering the hassle I had before the last repair attempt I asked for return and refund, providing several guiding logs and pictures and doing experiments with two different scope setups. This was denied.

Mr Mesu keeps claiming “other equipment” as the possible source of error even though the scopes work on other mounts and no scope/guider works on the Mesu mount. He also claims to have done extensive tests of my mount but will not provide any documentation. This has become a very frustrating experience and has cost me more than 40 of hours of clear sky time. I will now turn this over to a lawyer.

[Zakalwe]

Hi  Torben,

I have had a similar experience, so I understand your frustration.

A couple of things....RA drift can be solved pretty easily. If you use PHD V2 then you can use the Guiding Assistant to accurately measure the drift amount. You can then calculate the change that you need to enter in the SciTech config tool. See this post on how to calculate the amount that you need to add or subtract in the Tick field to correct the drift:

Quote

I previously had problems with my RA guide speed being too slow and as a result PHD was correcting RA always in the same direction and could not guide efficiently.

I decided to use Artemis (my ccd capture software) to track a star for 10 minutes and determine how many pixels it moved .

I made sure that my RA axis corresponded with the up and down lines of my cross-hair in Artemis and then slewed a star to the middle of the cross-hair.

I then placed my mouse pointer on the middle of the star and read the pixel number shown at the bottom right of the Artemis software window (for RA the pixel number is the second one)

After 10 minutes I placed the mouse pointer on the middle of the star again and jotted down the new pixel number.

I subtracted the first number from the second.

In my case the star moved up and moved 91 pixels.

I then multiplied 91 x 1.11 (the pixel scale of Atik 383 and Quattro 10")

This gave me 102 Arc-seconds of movement in 10 minutes.

Lucas Mesu Kindly helped me out with the next bit and I eventually managed to understand the Maths.

I launched Servo Config and  clicked " Edit Parameters" to get the data from my controller.

My number of ticks per scope revolution in the Ra Motor was 7949474.

In 10 minutes the Ra makes 9000 Arc seconds.

This is the Maths as explained by Lucas:

In 10 minutes the Ra makes 9000 Arc seconds.

Divide the error (102) by 9000=0.0113333333333333

0.0113333333333333 x 7949474=90094

7949474 - 90094 = 7859380

7859380 is the new number to put in the Ra Ticks per scope Rev window in servo config.

In my case this made it worse so instead of subtracting 90094 from my original ticks per revolution of 7949474, I added it to obtain my corrected number of 8039568.

Now my mount is tracking efficiently in Ra too and my guiding problems have been sorted too.

If you use the PHD Guiding Assistant then it will take the first couple of steps out as it will give you the drift amount that it is out by.

Regarding the handset- contact SciTech directly. They did have a bad batch of handsets so you *might* have one of those. I had one replaced by Dan at Scitech- no questions asked and they paid for shipping and the handst. They are a great bunch of guys to deal with....nothing is too much hassle for them.

 

Fingers crossed that you get it sorted.

[Staring]

The guiding assistant idea will not work because the drift is not constant, so this will not fix things. I am currently convinced that the clutch design of the Mk2 is faulty and can cause slippage, but this is my layman‘s explanation.

I have put far too much work into this and contact with the manufacturer has become more and more unpleasant the more it became clear the mount is the issue. It took three weeks to get him to fix the DEC encoder, and whatever he did in RA (the information oscillates between „nothing“ and torque adjustment) did not address the drift at all. He has now started to claim the first repair was only because of DEC problems while my first mail was titled „Drift in RA“. Extensive testing of the mount after repair is claimed, but no documentation of this is produced even after I repeatedly asked for it.

I have contact to several other people with similar experiences. Since this hobby is supposed to be fun I decided to „outsource“ further anger by contracting a lawyer to deal with it.

[Staring]

I‘ve had extensive help from the Sitech mailing list sorting out my problems with the factory configuration (that was unusable except for „no pier flip“ configurations - maybe works for an 80mm Apo). The Sitech software has a learning curve, but once I got used to it, I have come to appreciate the functionality and it blends into the background.
 

I did not know about the possibly faulty hand controllers, but I find it strange that one is expected to hunt down the Mesu supply chain to get replacement parts and configuration instructions - great and helpful as those guys may be.

[tooth_dr]

On 16/02/2021 at 17:13, Staring said:

The “Blinky” problem was solved with replacement of the DEC encoder

I did a search and found your thread @Staring

I have a feeling I have a similar issue here in that my DEC encoder has went faulty (or at least something is causing it to be faulty).  Can you give me any more info on the encoder and the replacement?

Thanks

Adam.