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Old 18-04-2017, 01:31 AM
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billdan (Bill)
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Mesu 200 up and running - Woo Hoo

Mesu 200 GEM Review

I believe I'm the first person to own one of these mounts in Australia and there are only a few in the southern hemisphere.

The Mesu 200 Mounts are hand made by Lucas Mesu (Mesu Optics) in Amsterdam and he also configures the mount firmware for your location. He uses TNT Air Freight to have them shipped to Australia and after GST is paid TNT delivers to the door.

For those unfamiliar with this mount, it is a friction feed mount (i.e a small diameter steel pinch roller pressed against an approx 250mm diam steel disk on each axis). By using this technique, gear backlash is eliminated and periodic error is very low. There is no need for East heavy with this mount, just normal balance. This mount has no clutches so balance is important, there are however hooks that can be locked into place when parked to stop any movement.

The mount has a payload capacity of 100Kg (four x C14 OTA's plus change) and utilises two encoders on each axis. The servo motor encoders are 8 million ticks (0.162arcsec resolution) and the axis shaft encoders are 10,000 ticks (2.16arcmin resolution).

The mount can be used at the equator as its latitude range is from 0 to 90 degrees.

It is supplied with a SiTech Mount controller and when you look at the 235 page manual it is very intimidating but Lucas sets everything up so you don't really need the big manual except for reference. A quick setup pdf manual is also emailed and I followed that procedure (what files to download etc).

Its stated pointing accuracy is < 2.5 arc mins with a single star alignment, and this can be further reduced by doing a PointXP star model. Its Goto speed is 8 degrees per sec at max slew.

It has an internal USB to serial converter for PC comm's, and another serial port for focuser/rotator, an ST4 port, plus the hand controller port. SiTech has its own database of stars and objects but most users link up with CdC for goto's and sync etc.

The options I purchased was the ADM Saddle, and the adapter plate, you can also optionally buy this mount dividable, the RA section weighs 15Kg and the DEC section weighs 11Kg, as my Mesu will be permanently in the Obs I chose not to buy this option. I didn't buy any counterweights so I had to make my own.

Sleeving 5kg Olympic plates that cost $10 is a lot less expensive than the commercial 5Kg counterweights at $100 plus freight . However I will probably buy some eventually to make it look nice.

After I received the mount the first step was to get the adapter plate drilled with four countersunk holes and with the EQ6 Tripod two holes drilled and tapped.

I also printed off some plastic sleeves for the weights, 50mm outer diam and 40mm internal diam to slide along the 40mm counterweight shaft.

While Cyclone Debbie was running amok I tested the mount in the laundry to make sure the laptop could control it OK.
When the weather settled down I installed everything in the Obs and started testing under near full moon.

Continued
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  #2  
Old 18-04-2017, 01:33 AM
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billdan (Bill)
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When the mount is switched on, it does not start tracking until either a star is synced, or an unpark command is given or manually switched on (blind tracking).
So after my very first switch on I hand-pad slewed to Canopus and then selecting Canopus from the scitech database, the star is synced and the mount then knows where it is in the universe. I then set up a park position and saved it. Incidently the Scitech hand-pad works differently than the EQ6, it seems that S is the top button and E is the left button. Just have to imagine yourself facing Sth and the buttons fall into place. Either that or I missed a check box somewhere.

From then on, if I use unpark and the scope hasn't moved then I can goto a target immediately. Using platesolving2 and sync you can centre the target very quickly.

Now it was onto drift aligning at the meridian and DEC 0.

The Mesu azimuth knurled nuts are easy to turn, you have to untighten the central tommy nut slighty first, adjust for PA and then re-tighten the nut. The elevation section has a coarse adjuster with holes that a pin goes through located every 10 degrees of elevation. The knurled nuts are then turned to get the elevation angle precisely tuned in.

While I was in an alignment mood (not much else you can do under full moon), I adjusted the cone error screws on the dovetail closest to the mirror. The first gem flip I was 8 arcmins off in RA (using platesolve2) and after repeated gem flips I adjusted it down to 20 arcsecs.

I did a set of PHD runs to see what the performance is like and compare to my EQ6. You can see the size difference here, not that much in height but a much longer counterweight shaft on the Mesu

Continued
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Old 18-04-2017, 01:37 AM
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billdan (Bill)
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Comparing an EQ6 with a Mesu is bit unfair, EQ6 costs about $2000 new and the Mesu is about $9000.
However The EQ6 is the only mount I can compare the Mesu with, having owned DOBS previously.

Attached are the unguided PHD graphs (running guide assistant) with a 3sec exposure time makes the total time of the graph approx 1285 secs (21.5 mins).

The EQ6 PE exhibits wild swings and doesn't appear consistent, making PEC pretty much useless. No idea as to what happened with RA and DEC taking off in that 3rd worm cycle (gust of wind maybe??).

By comparison the Mesu unguided graph is almost flat at the same graph scale of the EQ6. I have also attached the zoomed in version of the Mesu (graph and dartboard).
I was really pleased by this unguided performance - 0.72 arcsec overall RMS tracking and 2.5 arcsec Peak to Peak in RA.

The EQ6 closes the gap when guiding however, attached is one of my better guiding graphs and I normally get 0.7 to 1.00 arcsec guiding depending on star coordinates and seeing.

I tried the Mesu with SGPro to test PHD dithering and the Mesu comes in at 0.40 acrcsec RMS, I haven't tuned PHD to the mount yet, only dropped the aggression down to 40% to reduce overshooting. I did add the backlash stats and the graph for you to see.

Since I did these tests I had a play with Platesolve2 and its is great, it appears to makes star pointing models redundant.

Overall I am very happy with the purchase its tracking and goto's are accurate and it can handle a heavy load, so I highly recommend it.

I have a 14in F4.6 Skywatcher that I intend to get mounted onto the Mesu. Have to now find a carpenter to make me some big scope rings and buy a long Losmandy dovetail.

Cheers
Bill
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Old 18-04-2017, 02:23 AM
glend (Glen)
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Very nice mount Bill. But seriously, on an EQ6 tripod? That head unit should be on a pier with its capacity and your plans for a 14" scope on it. If it has to be a tripod you could probably buy an EQ8 tripod separetly. Maybe i missed something in reading your posts about your plan for that tripod. Having owned a NEQ6 i know what the tripod is capable of, and it seems to be a weak link in your setup.anyway that's just my opinion. Have fun, and lets see some nice images.
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Old 18-04-2017, 08:37 AM
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billdan (Bill)
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Thanks Glen, the tripod is only temporary until I can organise a pier. I want to put the 14in up there, to get an idea of what eventual pier height I need. As to how low I can get away with.

Bill

Last edited by billdan; 19-04-2017 at 12:47 PM.
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Old 18-04-2017, 06:51 PM
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Slawomir (Suavi)
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Looks very good Bill, looking forward to reading more about your experiences with Mesu
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Old 18-04-2017, 07:54 PM
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RickS (Rick)
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Nice looking piece of machinery, Bill!
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Old 19-04-2017, 12:49 PM
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billdan (Bill)
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Thanks Suavi and Rick, if you are ever driving past this way, drop in and have a look. Just send me a PM and I'll make sure I'm here.
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Old 22-04-2017, 03:03 AM
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Congrats Bill imho the best mount money can buy. Great to see one of these in Australia , it's one of my favourite mounts and uses the Sitech system of which I am a big fan. The only thing i don't like is for the price the look of the mount. As an engineer I appreciate practical over visual appeal, but Again for the price I feel it just looks a bit undressed to me. Then again for the price the capacity and accuracy are hard to beat. If I ever part with my Pentax MS5 (planned for observatory install) this would easily be its replacement no doubt.
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Old 22-04-2017, 09:22 PM
garymck (Gary)
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I have only about 6 weeks or so for mine to arrive......hanging out badly...
cheers
Gary
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Old 22-04-2017, 11:23 PM
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Btw another alternative goto system for this , might be Gemini or Gemini2. If you need a standalone more portable system I thin the Gemini could be made to work as both use servo motors. I have had my G11 operate with both systems using Losmandy servo motors, just had to rewire for the Sitech.
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