Re: Mesu 200 Mk2 Tracking stops close to equator



Sorry to hear that you’re having so many problems.  

If you are getting constant drift in one direction then there are not many possible causes. Namely:
  • Poor polar alignment.
  • Wrong tracking rate.
  • Significant imbalance of the mount which may be causing some slippage.  This would not normally be an issue with a worm/crown gear mount but, as far as I can understand, the Mesu mount has some sort of clutch for the direct drive.

If you are getting jumps superimposed over the drift, then I can only see the following possible causes:
  • Mechanical problems with the mount.
  • Guiding overshoot (if you’re guiding).
  • Guiding which is trying to follow the seeing because guide exposures are too short.
  • External factors such as wind.

I don’t know if you have done this yet but I suggest you try to graph your drift without applying any guiding corrections at all.  Do not use a mount model.  In Maxim, you simply set the mount to guide, set aggressiveness to zero and do a tracking graph over several worm cycles.  This means you will get the periodic error superimposed on the drift and quick jumps but you should essentially see a line which goes in one direction with respect to time.  With SiTech you can adjust the tracking rate based on the following note from Dan (which I posted a few days ago):

"If it ALWAYS drifts the same amount for anywhere in the sky, I would check my ticks per rev, also use a time server, and software that keeps updating your clock.

You can manually edit your SiTech.cfg file (make sure you're not running SiTechExe when you edit the file).

Look for the variable labeled "RightAscensionRate=0"
Change the zero to whatever you want.
This is in arc seconds per second, can be negative.

This is a little laborious because you need to close SiTech each time, alter the config file and start SiTech again but you can get the hang of it fairly quickly.  If you can tame the drift then you will be left with the jumps and the PE.  The PE you can correct by guiding but the jumps are potentially a major hurdle if they’re due to mechanical issues.  Correcting fast jumps is very hard.  About the only thing you can do is to use an adaptive optics setup but this means extra costs and messing around and to correct quickly (say, at a few Hz) you need quite bright stars.

Hope this helps.


On 17 Feb 2021, at 16:44, T. van Hees <torben@...> wrote:

Hello again. I am grateful for all the assistance I got in this community, so here is my most recent data. In the link you can find two of my recent guiding logs. Many of the log parts are with dithering because I just let Voyager run for the rest off the night, as I could not get the drift under control. I just took very short exposures with the RASA so got some data nevertheless. There is one run of Guiding Assistant, also attached as a screenshot. Within the logs, there is one run where DEC stops responding to guider commands: This is due to me not correctly tightening a clutch, not a mount error.

You will find RA drift between 2.5" and 14"/minute as well as some 20-30s spikes. I have tested again with a lighter and proven setup (my RC8 with OAG). I have currently no access to the log but I can describe the results: The 30s-spikes are far smaller, barely detectable (0.2" instead of 1"), but the RA drift was the same. DEC always seems to correct fine with both setups. That same setup works without problems on a Heq-5, so I think I can safely ignore a flex error. I realise longer logs might be beneficial to diagnose what exactly is wrong with the mount, but I can not present those. I have no more interest to tackle this problem and am in the process of contracting a Dutch lawyer to try and settle the whole mess for me and cut my losses. Dealing with Mr Mesu has been tedious and exhausting. I want nothing more to do with him and his business. I feel sorry that more people than just me are affected.

Links to logs:

Join to automatically receive all group messages.