A visit to Lucas Mesu's workshop

[gorann]

This spring I bought a used Mesu 200 Mk-I (of the first black edition) from @ollypenrice in southern France, who sent it on to Lucas Mesu in Holland for an upgrade, involving fitting a Sitech II controller to it and give it a general check-up. I went for the Sitech II since that is what I have on my current Mesu 200 Mk-I, and having identical systems would reduce the risk of midnight confusion. When he told me the mount was ready to be delivered, he asked if I wanted to pick it up. From my house in central Sweden that would be a 15 hour (1400 km) drive, so my fist thought was to have it shipped here. But then I realized that my wife had planned a trip for us to Denmark in July to see her relatives, and that would bring us half way to Lucas' workshop. So I said yes, and thought that this would be the safest way to get the mount to its new home. Lucas and his wife provided us with a very nice lunch, and we had a pleasant chat about life in general and mounts in particular.

There were very few Mesu 200 to be seen in the workshop as he had recently delivered the latest batch. He works alone in the workshop and said he produces about 40 mounts in a year. However, I got to see a Mesu 300, one of only two he ever made. The other one had been bought by a university and the one he has kept is used for calibrations.

Lucas was currently testing out using stepper motors as an alternative to the servo motors on the Mesu 200 Mk-II (image below). He is using Nema 17 stepper motors and a gear reduction of 1050 to 1. The Servo Motors have 2800 to 1 because of the higher dynamic range of the motors. According the Lucas' calculations the stepper motors can provide a slew speed of 3 degrees/sec or more and with micro stepping still smooth guiding, but that has to be tested with a suitable controller and controller board. He says that the Maxon servo motors with encoder and Sitech I controller will still be the standard configuration. An advantage with the stepper motors is that they can easily be controlled by various open source systems and some customers have expressed interest in such an option.

Cheers, Göran

 

Edited July 30, 2022 by gorann

[Jonk]

53 minutes ago, gorann said:

An advantage with the stepper motors is that they can easily be controlled by various open source systems and some customers have expressed interest in such an option.

I’ve also heard this. Very good idea to have alternative options.

Nice looking ‘proper’ workshop too!

[ollypenrice]

Before I ever saw a Mesu mount I was told by Maurice Toet, 'Lucas Mesu does his homework.'  He does, as well.

Olly

[newbie alert]

The sitech system has been foolproof for the mesu mounts, armed with the maxon steppers and encoders ,as mesu owners say they just work.. no need to dabble or fettle

Maxon produce really good motors, so good that they're used on the Rover and helicopter on the Mars mission..

I see using NEMA 17 steppers on a fail-safe system as a backward step, yes they can be used on open source systems but some of those systems don't support using encoders as a example.. not sure on the moxan motors cost wise but NEMA 17 are really cheap (£20 ish for 2) and can be purchased anywhere from steppersonline , Amazon and eBay.. don't think you can buy a moxan from those sources ... The mesu is a quality product, made and setup with quality products and software, can't see cheaper products working on the same level of quality..

The trident did start off spec wise using moxan motors, sitech encoders etc, now the spec has changed to using NEMA 17,Onstep software etc

 

[Jonk]

1 hour ago, newbie alert said:

The sitech system has been foolproof for the mesu mounts

Sorry, can’t agree with this. There are a couple of outstanding issues with Sitech that Dan Gray has been aware of for months and hasn’t managed to fix yet.

 

[newbie alert]

53 minutes ago, Jonk said:

Sorry, can’t agree with this. There are a couple of outstanding issues with Sitech that Dan Gray has been aware of for months and hasn’t managed to fix yet.

 

Does that mean that it doesn't work? I've not read any negatives from mesu owners.. only ever positives... 

All I was trying to say was  in my opinion downgrading the motor's, changing the system to more open source is a step in the wrong direction ..

[tomato]

Thanks for your visit report. I note that you said Lucas works alone in the shop and he produces about 40 units per year. I do hope he can grow the business sufficiently so he doesn’t have to remain a one man band, which often seems to be the case with the inventors of unique and exceptional items of engineering in the astronomy world, and the consequences that arise when the source of the knowledge and expertise resides with just one individual.

I just read today that there are three key individuals at Sidereal Technology, the manufacturers of the Sitech units, one is a retired NASA Space Shuttle Mission Director, no less.

[whipdry]

7 hours ago, Jonk said:

Sorry, can’t agree with this. There are a couple of outstanding issues with Sitech that Dan Gray has been aware of for months and hasn’t managed to fix yet.

 

I'm guessing this is about using what is a German Equitorial Mount without the need of a meridian flip... not sure this issue is Dan Grays fault as he didn't make the mount, but do agree he's the only person who can fix it! 

What's the other issue? 

 

Peter

[tonyowens_uk]

On 30/07/2022 at 13:15, newbie alert said:

The sitech system has been foolproof for the mesu mounts, armed with the maxon steppers and encoders ,as mesu owners say they just work.. no need to dabble or fettle

Maxon produce really good motors, so good that they're used on the Rover and helicopter on the Mars mission..

I see using NEMA 17 steppers on a fail-safe system as a backward step, yes they can be used on open source systems but some of those systems don't support using encoders as a example.. not sure on the moxan motors cost wise but NEMA 17 are really cheap (£20 ish for 2) and can be purchased anywhere from steppersonline , Amazon and eBay.. don't think you can buy a moxan from those sources ... The mesu is a quality product, made and setup with quality products and software, can't see cheaper products working on the same level of quality..

The trident did start off spec wise using moxan motors, sitech encoders etc, now the spec has changed to using NEMA 17,Onstep software etc

 

Quality of a motor or a motion controller has little to do with its cost. Stepper motor and servo motor drive systems have their own strengths and weaknesses, and in some applications the motor technologies can be blended (servo-stepper). What matters is the motion quality delivered, and the reliability and maintenance requirements. There is no reason I can think of why a microstepped Mesu friction mount should not track as well as the Maxon skewed-rotor/Scitech model, particularly if closed-loop steppers (servo-stepper technology with embedded encoder) are chosen. 

You seem to suggest that the Onstep control software is inferior to Scitech's.  Do you have evidence for this?

[newbie alert]

Thanks Tony for your reply, no it's not directly cost related answer but like you said yourself steppers and servos have strengths and weaknesses, I could ask you the same thou, are you implying that the nema17 is as equal in quality as the moxan motors? Why wasn't NEMA 17 used on the rover or helicopter on mars?

Do you believe that Onstep is either on par or superior to Sitech?.. if so why can't  absolute encoders be used with Onstep at this present time, maybe sometime in the future

At the moment for Lucus the system that he's using with the mesu has proven to be pretty failsafe... I hope that continues to be the case for him

These are the reasons, not a direct cost related answer but as you know, quality components cost that little bit more than cheaper mass produced items

The friction driven trident is now being used with NEMA 17 and Onstep, which wasn't the original spec, do you think that was because of anything other than cost.. mark continues to sell encoders for these mounts even thou they can't be used at this present time

Edited August 1, 2022 by newbie alert
Added info

[tonyowens_uk]

6 hours ago, newbie alert said:

 I could ask you the same thou, are you implying that the nema17 is as equal in quality as the moxan motors? Why wasn't NEMA 17 used on the rover or helicopter on mars?

 

Hi newbie! I dont think its meaningful to speak of the quality of a motor or any other technical component in the abstract. A 200 step/rev hybrid stepper motor cant be compared to a brushed DC servomotor without looking at the context. If that is running an axis of a telescope mount, we are looking at torque vs speed characteristics, electrical efficiency, noise emission, 'cogging' behaviour, spindle positioning elasticity (drive stiffness), robustness, wear life, ease of packaging, ease of commissioning and reliability. And in this application no meaningful comparison is possible without also including the motor drive electronics, cabling, connectors and firmware. On one side we have Maxon/Scitech and industrial sealed connectors and screened cabling. On the other, we might have a Chinese generic 400 step/rev NEMA17 hybrid stepper driven by a Trinamics TMC2209 driver and commanded by Onstep running on a modern ESP32 embedded controller, with unshielded and unsealed motor wiring. Or it might be a similar controller board operating a Clearpath SDSK stepper-servo with 6400 tic embedded encoder via Onstep's step/direction interface, and wired with silicone-sheathed shielded cable and metal IP65-rated M12 multipole connectors.

In terms of measured following error during tracking (motion quality), the difference between these three solutions may well be negligible. Autoguiding compensates perfectly for the lack of a high-resolution axis encoder on all of these solutions. The torque capacity superiority of the stepper solutions is irrelevant as input torque capacity of Mesu's friction drive will limit how much motor torque can be delivered. The speed advantages of the servo are irrelevant as the steppers can 'pull' higher overall transmission gearing if necessary. As the friction transmission is (as I understand) backdriveable, the efficiency of the stepper-based drivetrain may be more efficient if the mount spends significant periods held stationary. Or not, as the case may be. There will be no difference in noise emission when tracking between these mounts except for the servo's faint 20 kHz commutation whine. None of these systems will exhibit cogging behavior visible in images (provided the servo is properly tuned with a small 'deadband' of about +/- 2 encoder counts and provided the Trinamics driver running the simple stepper has plenty of drive current available).

One big difference between the simple stepper system and the other two (servo and servo-stepper) might be drive (motor rotor) positioning stiffness. Whether far superior rotor stiffness of the latter solutions provides any benefit will depend on the amount of friction in the Mesu's transmission. As this is far lower than worm drive mounts, for example, it may well be that there is no perceptible difference. But in a worm drive mount, especially of the antibacklash type where drag friction is significant, a difference is likely to be apparent in rms guiding error.

 Another difference emerges when looking at ease of commissioning. The Scitech servo system needs careful tuning to obtain stability without micro-oscillation at tracking speed or sluggish response to positioning moves, which makes building the systems more involved. None of these systems (so far as i'm aware?) employ speed reduction gearheads so all should be equally reliable. The only one that is environmentally-sealed to normal industrial standards for outdoor use (advisable for remote-controlled observatories for example) would be the servo-stepper one I mentioned with waterproof connectors.

So there you have it. There is a very big difference between the cost of these three systems, the Scitech one being most costly by far. This is easily explained by:

1. the manufacturing economics of the relevant component suppliers
2. the avoidance of the need to recoup very substantial R&D costs on the Onstep system which is a GPL development that is designed to run on COTS hardware
3. the fact that there are multiple parties involved in the supply chain for Scitech which leads to greater margin-taking

For many end-users, performance differences between these systems will not be apparent, meaning that there is no perceptible diffrence in 'quality'. For a minority of users who need the greater simplicity of repairs and maintenance of the stepper system e.g. remote controlled imagers, that might be a better choice for them. For another minority who are interested in remote satellite tracking and orbital parameter calculations and need high dynamics, a servo-stepper system might be their choice. And perhaps a few (like me) admire the form and finish and heritage of historical highly-engineered assets - for us, the existing Maxon/Scitech solution is also appealing.

 

Tony Owens

[newbie alert]

All that to agree on the maxon/Sitech setup🤪🤔🙄

[tonyowens_uk]

1 hour ago, newbie alert said:

All that to agree on the maxon/Sitech setup🤪🤔🙄

No. Dignify the discussion by reading my essay.
All that to try make a case for:

• more thoughtfulness about terms like quality in highly engineered systems
• the avoidance of loose language and the lazy equation of cost with quality
• and to discourage the casual dissing of the work products of other people (e.g. Onstep) without evidence!

Best

Tony Owens

[newbie alert]

8 hours ago, tonyowens_uk said:

No. Dignify the discussion by reading my essay.
All that to try make a case for:

• more thoughtfulness about terms like quality in highly engineered systems
• the avoidance of loose language and the lazy equation of cost with quality
• and to discourage the casual dissing of the work products of other people (e.g. Onstep) without evidence!

Best

Tony Owens

If you took the time to read my short message I mentioned a few times that it wasn't a directly about cost.. and the reasons why about Onstep..  it's not my fault you chose either not to read or absorb it or to skirt around it like it wasn't there.. 

[wimvb]

On 30/07/2022 at 11:37, gorann said:

that would be a 15 hour (1400 km)

Wow, that's fast. I've driven that stretch a few times (well, almost that stretch), but don't think I 've ever come close to keeping almost 100 km/h for the average. 😉 😉

Great write up, btw.

As @tomato already hinted at, my concern with Mesu (company/product) would be, what happens when he (the person) decides to call it a day and retire from his business? Even if he sells the company and designs, that won't mean much without the expertise behind it all. So far it seems that Mesu mounts are very durable, but what if a mount needs service after Lucas retirement? The mounts are of excellent quality, as shown by their track record. But it's not only the product that's important, but the entire supply chain during the product's lifetime.

Just wondering...

[tomato]

Yes, it is a concern. However, the scarcity of clear nights in the UK probably means I will need a service before the mount does.

[Zakalwe]

On 30/07/2022 at 16:00, newbie alert said:

Does that mean that it doesn't work? I've not read any negatives from mesu owners.. only ever positives... 

 

You should extend your reading horizons then. There's a very long thread on here detailing serious issues that I and others have had with this system. The resolution took many months to sort out and only with the persistence of the users and Dan Gray's exceptional help. The experience pretty much killed my enthusiasm for this hobby for a number of years.

[wimvb]

25 minutes ago, Zakalwe said:

You should extend your reading horizons then. There's a very long thread on here detailing serious issues that I and others have had with this system. The resolution took many months to sort out and only with the persistence of the users and Dan Gray's exceptional help. The experience pretty much killed my enthusiasm for this hobby for a number of years.

I feel with you. I’ve been close to throwing in the towel several times. Fortunately the engineer in me wouldn’t give up. With high end gear, this shouldn’t be an issue. But it seems that regardless of how much we throw in the money pit, there will be frustrating moments.

[gorann]

3 hours ago, wimvb said:

Wow, that's fast. I've driven that stretch a few times (well, almost that stretch), but don't think I 've ever come close to keeping almost 100 km/h for the average. 😉 😉

 

He he, I think I also spent a bit longer on the road, but since I did not keep much track of time I just posted the estimated time by Google maps.😉

[Astroscot2]

3 hours ago, Zakalwe said:

You should extend your reading horizons then. There's a very long thread on here detailing serious issues that I and others have had with this system. The resolution took many months to sort out and only with the persistence of the users and Dan Gray's exceptional help. The experience pretty much killed my enthusiasm for this hobby for a number of years.

Hello Stephen.  good to see you back, are you still imaging with the Esprit?

 

Mark

[Zakalwe]

19 hours ago, Astroscot2 said:

Hello Stephen.  good to see you back, are you still imaging with the Esprit?

 

Mark

Hi Mark,

Thanks for the comment. I moved house almost exactly 12 months ago, so still haven't got the observatory back up and running, though I did finally manage to get a solarscope out the other day.

With a bit of luck and focus I should be back in action soon. And yes, I still have the Esprit 120 ;-)

[SimonIRE]

On 01/08/2022 at 15:08, tonyowens_uk said:

Hi newbie! I dont think its meaningful to speak of the quality of a motor or any other technical component in the abstract. A 200 step/rev hybrid stepper motor cant be compared to a brushed DC servomotor without looking at the context. If that is running an axis of a telescope mount, we are looking at torque vs speed characteristics, electrical efficiency, noise emission, 'cogging' behaviour, spindle positioning elasticity (drive stiffness), robustness, wear life, ease of packaging, ease of commissioning and reliability. And in this application no meaningful comparison is possible without also including the motor drive electronics, cabling, connectors and firmware. On one side we have Maxon/Scitech and industrial sealed connectors and screened cabling. On the other, we might have a Chinese generic 400 step/rev NEMA17 hybrid stepper driven by a Trinamics TMC2209 driver and commanded by Onstep running on a modern ESP32 embedded controller, with unshielded and unsealed motor wiring. Or it might be a similar controller board operating a Clearpath SDSK stepper-servo with 6400 tic embedded encoder via Onstep's step/direction interface, and wired with silicone-sheathed shielded cable and metal IP65-rated M12 multipole connectors.

In terms of measured following error during tracking (motion quality), the difference between these three solutions may well be negligible. Autoguiding compensates perfectly for the lack of a high-resolution axis encoder on all of these solutions. The torque capacity superiority of the stepper solutions is irrelevant as input torque capacity of Mesu's friction drive will limit how much motor torque can be delivered. The speed advantages of the servo are irrelevant as the steppers can 'pull' higher overall transmission gearing if necessary. As the friction transmission is (as I understand) backdriveable, the efficiency of the stepper-based drivetrain may be more efficient if the mount spends significant periods held stationary. Or not, as the case may be. There will be no difference in noise emission when tracking between these mounts except for the servo's faint 20 kHz commutation whine. None of these systems will exhibit cogging behavior visible in images (provided the servo is properly tuned with a small 'deadband' of about +/- 2 encoder counts and provided the Trinamics driver running the simple stepper has plenty of drive current available).

One big difference between the simple stepper system and the other two (servo and servo-stepper) might be drive (motor rotor) positioning stiffness. Whether far superior rotor stiffness of the latter solutions provides any benefit will depend on the amount of friction in the Mesu's transmission. As this is far lower than worm drive mounts, for example, it may well be that there is no perceptible difference. But in a worm drive mount, especially of the antibacklash type where drag friction is significant, a difference is likely to be apparent in rms guiding error.

 Another difference emerges when looking at ease of commissioning. The Scitech servo system needs careful tuning to obtain stability without micro-oscillation at tracking speed or sluggish response to positioning moves, which makes building the systems more involved. None of these systems (so far as i'm aware?) employ speed reduction gearheads so all should be equally reliable. The only one that is environmentally-sealed to normal industrial standards for outdoor use (advisable for remote-controlled observatories for example) would be the servo-stepper one I mentioned with waterproof connectors.

So there you have it. There is a very big difference between the cost of these three systems, the Scitech one being most costly by far. This is easily explained by:

1. the manufacturing economics of the relevant component suppliers
2. the avoidance of the need to recoup very substantial R&D costs on the Onstep system which is a GPL development that is designed to run on COTS hardware
3. the fact that there are multiple parties involved in the supply chain for Scitech which leads to greater margin-taking

For many end-users, performance differences between these systems will not be apparent, meaning that there is no perceptible diffrence in 'quality'. For a minority of users who need the greater simplicity of repairs and maintenance of the stepper system e.g. remote controlled imagers, that might be a better choice for them. For another minority who are interested in remote satellite tracking and orbital parameter calculations and need high dynamics, a servo-stepper system might be their choice. And perhaps a few (like me) admire the form and finish and heritage of historical highly-engineered assets - for us, the existing Maxon/Scitech solution is also appealing.

 

Tony Owens

This is really interesting, thanks

[dan_adi]

On 02/08/2022 at 10:42, wimvb said:

Wow, that's fast. I've driven that stretch a few times (well, almost that stretch), but don't think I 've ever come close to keeping almost 100 km/h for the average. 😉 😉

Great write up, btw.

As @tomato already hinted at, my concern with Mesu (company/product) would be, what happens when he (the person) decides to call it a day and retire from his business? Even if he sells the company and designs, that won't mean much without the expertise behind it all. So far it seems that Mesu mounts are very durable, but what if a mount needs service after Lucas retirement? The mounts are of excellent quality, as shown by their track record. But it's not only the product that's important, but the entire supply chain during the product's lifetime.

Just wondering...

I have/had the same concerns, but given that there are mesu mounts 10 years old and still working, I think you are safe. After 10-15 years of using it, if it fails, you can buy another brand. Or you could have 2 mesus, one for backup...