Mesu 200 vs Avalon

[Earl]

Im starting to look at mounts, the Mesu has been very highly rated but the Avalon Instruments Linear Fast Reverse Equatorial Mounting is EQMod compatible, less capacity but that's not really a major issue.

Any thoughts?

[nmoushon]

I've heard nothing but praise for the mesu 200, especially from Olly. I haven't heard much on the Avalon but would love to see how the belt drive really compairs the the worm drive and if it can stand toe-to-toe with mounts like the mesu and others in that price range. The load capasity its actually quite a gap. Roughly 50kg vs 20kg for imaging. The tracking on the avalon must be pretty damn good otherwise the extra 30kg the mesu can handle could easily be used for a great guide scope & camera. Just my initial thoughts though.

[ncjunk]

I'll let you know on the mesu as i get mine from modern astronomy on Friday...but it will take me a few days to get the weights drilled out and a couple of other things bodged onto it in my unique style.

I will be looking at how the Ascom driver performs and if it can park etc as my setup is automated.

[ampleamp]

Hi Earl, I can't comment on the Avalon, but when I was looking, Ian King was very complimentary about it; being EQMod compatable was certainly a considerarion for me as I think it is one of the best bits of control software out there.

I can however comment on the Mesu. My tuppence worth -

It is too early for me to do a full review, but one will be coming. I bought one with the intention of having the summer to learn it in preparation for autumn/winter etc, ha, ha. There is no doubt that the Argo Navis controller takes some time to come to grips with, but it is just different. I have largely come to the conclusion that it is best with the handset as it is just so easy. I have had it talking to and working from CdC; this was quite easy, but you do have to read the ServoCat instructions, especially when it comes to com ports (must be 1-16). There are multiple setup and control options in the AN handset, but in setup, you would only be using "Rough GEM" or "Exact GEM" with the Mesu.

Thanks to my very patient mentor, Bernard at Modern Astronomy, I now have a handle on "Rough GEM" as this requires three alignment points, one of which is "setup alt ref" which caused me some confusion. However, with time constraints and my niavety, I have just used "Exact GEM" as it only needs one alignment point; essentially as it was less hassle. Polar Alignment is something I will to do a lot better once I have a polar scope (and therefore be able to use "Exact" mode with some conviction), but for now I have just used the main scope as the polar scope and adjusted the mount accordingly. This is a pretty rough method and is a far cry from drift alignment or even Alignmaster. However, combined with one alignment star, a target has always been placed near/on the centre of the eyepiece/on camera and more importantly, the native tracking keeps it there easily.

Attached is a PHD graph, from Bernard, as foolishly, I never thought to save any, however, for a full review, I will use my own. My own tracking has been very similar at well under one. There are various tweeks you must remember, such as using an initial alignment star in the east, but other than that, it just works. It really is very easy to use, and extremely accurate.

Before I made my decision, I looked at all sorts of mounts including the obvious options, eg Paramount, AP, and some less obvious ones such as ASA. One of my main criteria was that I have no idea what scopes I may use in the future and having the safety net of the large capacity was essential as you aren't going to buy one of these every day or year. To me, the accuracy and capacity are a hard combination to beat. We spend enough ££ on scopes and cameras and filters and whatever else...., if the most important bit of kit you can have is the mount, then this has got to be up there.

Olly, I am sure, will give you much more detail as he has been using one for 4/5 months now and with his skies, that will be a lot of hours. I think I read somewhere that he did 32 hours of imaging on one subject and didn't throw a single sub. I am sure that this will be the mount to beat over the next few years.

[ampleamp]

Neil,

on the current versions, there is no park option with Argo Navis, that is apparently coming in the next upgrade, due this year. The ascom driver for ServoCat can be found following, http://www.unm.edu/~eschman/ The instructions are straight forwards; and coincidently (??) there is an upgrade coming for ServoCat as well. There is a lot of info on the iceinspace site re AN and ServoCat.

Hope you enjoy your new toy!

Alistair

[ncjunk]

Ok so its the servocat ascom driver I have then.

no park? isnt that part of the standard Ascom telescope driver functionality? (I know that you can disable commands you dont support when writing the driver as i did it with my focuser. so it may be it doesnt have it).

I'll check it out at the weekend....seriously no park?? I'll do a routine myself if i damn well have to.

there is a "planitarium position" function that can be filled with the ra/dec co-ordinates....hhhmm

[pete_l]

I've been looking at mounts, too. The fruits of my labour is the chart below. All I've done is plot payload against price. Obviously there are more attributes of a mount that are important - but there are few that are as objective and as widely quoted, hence the comparison.

The way it looks to me is that there is a "low cost" cluster of mounts at prices up to about £4,000. In that group the NEQ6 is hard to beat - even when you take other considerations into account: such as tracking and that ever-so-subjective "quality".

After that, there's the "heavyweights" that will take a 50kg + load.In that category the Mesu 200 is also hard to beat - especially with the sorts of loads that amateurs could plonk on it.

Finally, there's "all the rest", including most of the "quality" mounts: the Astro-Physics, Vixen and the other household names (well, in *my* household, at least).

There are lots of mounts NOT on the chart, especially ones that are hard to come by, in the UK & mainland europe - as I'm not particularly interested in those.

Just whether the chart is useful depends on how much each individual values "quality" or less well defined characteristics such as tracking abillity or ease of use.

[ncjunk]

I think if the Mesu doesnt have the ability to Park at the end of a run and power down then it may affect your choice.

In my observatory I kind of need this ability to retain position after power down so that i can start from the same position without having to do a resync or alignment.

This may mean i have to go to the observatory to do an initial alignment.

I believe if you leave it powered it will retain position but my observatory is being configured so that everything is automated including power.

I'll let you know what i find out.

[ampleamp]

Neil, when you are into pure automation, you are into realms I have no idea about; I know that vdb and Olly have mentioned this for the mount at Olly's site but the connection is too slow (?). You are right that if left on, the mount retains the information so should go back to position for another run at another time. I have never done this simply as I don't need to; setup and alignment is so quick that it just isn't necessary, but I am only having to walk 20yds .

If anyone is interested, I am more than happy to demonstrate the Mesu in action; pm me if appropriate.

[ollypenrice]

I can't comment on the automation side and Lucas Mesu will need to address this (he may already be doing so,

I don't know) in order to attract folks who want remote control.

The Mesu at my place (Yves' mount) has an adjacent warm room with bed in it and that's as remote as I like to get! Getting going is a cynch. Powered off, I swing the scope by hand to a bright star near (ish) to my target, centre it in the finder and power up, activate 'Align Star,' scroll to the right one and say Synch. That is always good enough to see the star on the chip when I go in and power up the camera. I quickly centre it (10 seconds?) and re-synch. Choose the object, say Go To and there it is on the chip - at 2.4 metres. Quick as this is, you might save thirty seconds by running through a planetarium until the night (come on, admit it!) when the planetarium just won't play. Then you'll wish you hand a handset and you will lose hours.

The Mesu is not just about payload. It has low, slow periodic error and no backlash at all. It is very, very well built and remarkably simple. As I said in my ATT review, 'If you want to know how it works, just look at it.'

Here's a tale I haven't had the time to tell, so far. Yves and I decided to try a monster tandem rig on the Mesu, namely the big ODK 14, some titanic Robin Cassady hardware, and a 7 inch Intes fast Maksutov for colour aquisition using a smaller pixel QSI. This little lot was just prodigious in size, weight and cumbersomeness. It didn't work, but that was not the fault of the Mesu. At the first attempt to balance it all we switched it on and the Mesu (with OAG on the ODK14) just did what it always does, which is track very nicely thank you. Unfortunately the project as a whole fell foul of the need to have the optical axes of the telescopes not only parallel but symmetrically equidistant from the mount axes, otherwise PA will get you. At least this is what we think was happening. At short FLs tandem systems are fine but with these brutes there are new factors in play. And maybe the Intes mirror was moving. However, however, the Mesu was doing exactly what it was being told to do by the autoguider. At least we know it will handle a big Plane Wave. Ahem, enough of that kind of talk!!!

I really like the look of the flipless Avalon, just as I like the look of the flipless Mesu. In my line of work fliplessness means time in bed.

If I were to sell the EM200, though, I simply wouldn't risk buying anything but a Mesu. I feel that I know it works. And yes, it is entirely routine to do 20 to 30 hour runs without losing a sub. I run it way past the Meridian, too.

Olly

[ncjunk]

Good to know as I fancy trying 2 large scopes at some point.

I know you dont like pc control but with the eq6 i can open the observatory and then set a plan running whilst it is light and i can then cook, do kids bed time and get ready for bed and my imaging runs faultlessly (thats a lie at the moment as i am messing with a qhy8l and cant get the damn thing to focus automatically....285 works fine when i have it connected). if there is a problem its normally usb cables.

if i have got to go out and spend half an hour doing an alignment i am er...done in...as it wakes me up (normally half asleep after kids bedtime) and means i lose beauty sleep and takes longer to get to sleep.

I can do all my alignment from the house at present if there is a problem.

it comes down to what fits in with your lifestyle and at the moment not having a park command would be a right pain in the rear.

although i have heard it is to be added to the firmware i want to find out when.

i may just leave it all powered if there are a couple of days good whether.

[ollypenrice]

Yes, I understand your point, Neil. Perfectly fair, and an automatable Mesu would certainly be a bonus for you. The 'two big scopes' experiment was instructive if disappointing. We ended up talking to others who had also tried and failed. The obvious solution is... two Mesus!!!!

Olly

[Jessun]

It has low, slow periodic error and no backlash at all.

I can see how the design has no backlash, but how come the PE is so slow? Is it due to the 'axis' of the motors resting straight onto the RA/DEC discs rather than having worm gears? I have tried to work out what actual RA/DEC movement per revolution of the turning worm/pin would do but can't get my head around this piece of simple physics... I would guess that a pin even with only a few mm diametre will move more than a big worm gear per revolution.

Is it perhaps just easier to make a perfectly round pin than a perfect worm assembly. Might be that simple.

Having seen more pictures of TS's mobile Mesu200 I like it more and more.... But it's not white. The images you chaps produce speak for themselves however...

[steppenwolf]

Is it perhaps just easier to make a perfectly round pin than a perfect worm assembly. Might be that simple.

This is the cruncher, surely? If you have a good lathe then the pin and 'wheel' can be made closer to perfect than any gear system? I also think that the 'stiffness' of the system has an effect here too.

[pete_l]

This is the cruncher, surely? If you have a good lathe then the pin and 'wheel' can be made closer to perfect than any gear system? I also think that the 'stiffness' of the system has an effect here too.

That's my understanding, too. The big imponderable is how well the metal on metal friction coupling holds up over time. It would only need one tiny speck of dust, or swarf to get into the wrong place and wear a pit, or get pressed into one of other surface to introduce irregularities into the drive. I guess that would depend on how well the drive mechanism is sealed from contaminants.

[ollypenrice]

That's my understanding, too. The big imponderable is how well the metal on metal friction coupling holds up over time. It would only need one tiny speck of dust, or swarf to get into the wrong place and wear a pit, or get pressed into one of other surface to introduce irregularities into the drive. I guess that would depend on how well the drive mechanism is sealed from contaminants.

The drives are very well sealed. I'm tempted to say 'totally' but that would not be very scientific!

When you think of the engineering challenges involved in making a very accurate worm drive they are quite daunting. End float on the spindle of a worm introduces PE. End float on a roller doesn't. But why single out the roller drive for special consideration regarding swarf or grit or other contminants? Such contaminants do affect worms as well. The very un-sealed worm in a conventional mount I'm using has picked up a bit of something, it seems, and has introduced a spike on each turn of the wheel.

It seems to me that the worm drive is a fundamentally bad idea despite the fact that it is almost unversally used in amateur mount designs. It is expensive to make, requires a grease layer and is inherently backlash-prone. Sometimes bad ideas survive for a long time in engineering. Motorcycle rear suspension used to be based on a pivoted fork. BMW scandalized the motorcycling world by switching to the scooter-style single sided arm which everyone thought looked all wrong. But it isn't all wrong, it has proved to be the way to go.

My Tak EM200 is incredibly sensitive to balance. But you can muck about, swapping things around on the Mesu, and it couldn't give a hoot. Roughly balanced is balanced and that's that. A few people have said 'I want one!' and, believe me, I want one too!

Olly

[Zakalwe]

Actually, worm drives are very easy and cheap to produce, hence that is why they are so ubiquitous. They can easliy be produced on a lathe (the worm is nothing more than an open thread and the worm-wheel can be made with a tap spinning at right angles to the centre of a disc).

As for single-sided swingarms on bikes? They are heavy, produce ridiculous torsional loads and have to be massively over-engineered to cope. Ever see the size of the wheel bearings required? BMW adopted them as they could incorporate a shaft drive (another abomination- heavy, produces torque reaction and induces loads into the suspension) into the arm. SSSA are really only found on tourers, as the huge extra weight, and torque reaction is worth the penalty as you can do away with a chain. there's a reason why 99.9% of raceing motorcycles do not have a SSSW...even Honda no longer use them (despite the RC30, RC45 and V-Twin NSR500V GP bike having them)

[pete_l]

But why single out the roller drive for special consideration regarding swarf or grit or other contminants? Such contaminants do affect worms as well.

Don't get me wrong, I'm not saying this tech is better than that tech. My point is that the Mesu is an outlier in the price/performance stakes (to be fair, so is the NEQ6 which is better/cheaper, as it appears to have raised the bar for cheapo GEMs, not because it's lower quality) and like all devices that appear to be a lot better than "conventional", tried and trusted solutions I want the tyres to be thoroughly "kicked" - preferably by other people - before I get my wallet out.

[ollypenrice]

OK, I'll stand corrected on swing arms though chain drive is only of any use on toy motorcylces intended for playing at Valentino Rossi on a Sunday!! Regarding the cost of worm drive, I'm not an engineer but there have been plenty of examples of higher quality worm and wheel sets being offered, so I conclude that they can't be that easy or cheap to make or Losmandy and SW would have got it right from standard, I'd have thought. The big objection is backlash. The belt drive idea is also very interesting on the Avalons.

In a nutshell Yves' Mesu is simply unlike any other mount I've either used or seen in use, it really is.

Olly

[Zakalwe]

OK, I'll stand corrected on swing arms though chain drive is only of any use on toy motorcylces intended for playing at Valentino Rossi on a Sunday!! Regarding the cost of worm drive, I'm not an engineer but there have been plenty of examples of higher quality worm and wheel sets being offered, so I conclude that they can't be that easy or cheap to make or Losmandy and SW would have got it right from standard, I'd have thought. The big objection is backlash. The belt drive idea is also very interesting on the Avalons.

In a nutshell Yves' Mesu is simply unlike any other mount I've either used or seen in use, it really is.

Olly

BMW didn't introduce parallelogram single sided swingarms....the Magni Le Mans was the first.

Chain drive is the most efficient way of transferring energy...in the region of 90%+. Its also cheap, light, and allows the rear wheel-to-swingarm spindle length to be adapted and the final drive gearing can be altered quickly and with great flexibility, In comparison, shafties are heavy, complicated, very inefficient (gears are about 80% efficient), do not allow rear wheel adjustment, do not allow final-drive gearing ratios to be altered, require the powertrain to be turned through 90 degrees at the gearbox output (more power losses and packaging isues) and require parallogram linkages to control the effect of the shaft trying to "climb" the hypoid rear wheel gear (which causes forces to be feed into the rear suspension of the bike). In effect, shafts are probably the worst possible solution for tranmitting power to a rear wheel.

Where sharfts are good, is in long service intervals and the fact that they are sealed (although chain drives can also be easily sealed). For this reason, and this reason alone, are shafts used on tourers. In every other respect, shaft drives are a much poorer solution to chanins. A chain drive is simply the most efficient, cost effective and adapable solution.

[/thread drift]

[ollypenrice]

Thread drift indeed! To lighten up a bit, my wife's MZ, years ago, had a handbook saying that it had an enclosed chain 'to protect the pillion passenger's hose...' Rather sweet, I thought. It also meant that the touring rider could have a change from eating oil sandwiches every day! 'Tourers' are what I distinguish from Sunday toys, I think. What about belt drive? Never tried it but if it doesn't break on a Buell I don't see it breaking at 1 RPD (revolution per day) on an Avalon.

Back to worm drive mounts, I suppose I feel they've had their chance and failed. Believe me, there isn't a single make of worm drive mount which I have not seen misbehave or whose owners have declared vice-free. Individual mounts, yes, but makes - no. That includes AP and Paramount and Takahashi and 10 Micron. I'm really looking forward to see how other Mesus perform and to hearing about the Avalons. Ian King is a good source of honest information which is a good start for Avalon.

Olly

PS Pub quiz time: what motorcycle had shaft drive with worm gears? (It wasn't a good idea!)

[Zakalwe]

What about belt drive? Never tried it but it it doesn't break on a Buell

Belts drives are very good, but also have some drawbacks.

The pros: Very long service life. Virtually zero maintenance. Clean in use (no lubrication required). Very efficient.

The cons: They cannot transmit as much torque as a chain (link widths being similar), and as a result they require a large rear wheel "sprocket". This increases the unsprung mass, which is a big no-no if you want efficient handling and suspension. They can slip if contaminated. In motorcycle usage, they need to be toothed. They generally require idling rollers to keep the belt tension correct. Finally, they fail catastrophically (and they do fail. Belts need to be changed strictly inline with the service schedule), whereas a chain gives loads of indications that it is wearing.

You tend to find belts on cruisers and Hardley Ablesons. They are suited to that type of low-powered applications (especially where handling and cornering are far less important in comparison to the number of tassles on the handlebars ) .

'Tourers' are what I distinguish from Sunday toys, I think.

You might want to tell Nick Sanders that....

[ollypenrice]

Belts drives are very good, but also have some drawbacks.

The pros: Very long service life. Virtually zero maintenance. Clean in use (no lubrication required). Very efficient.

The cons: They cannot transmit as much torque as a chain (link widths being similar), and as a result they require a large rear wheel "sprocket". This increases the unsprung mass, which is a big no-no if you want efficient handling and suspension. They can slip if contaminated. In motorcycle usage, they need to be toothed. They generally require idling rollers to keep the belt tension correct. Finally, they fail catastrophically (and they do fail. Belts need to be changed strictly inline with the service schedule), whereas a chain gives loads of indications that it is wearing.

You tend to find belts on cruisers and Hardley Ablesons. They are suited to that type of low-powered applications (especially where handling and cornering are far less important in comparison to the number of tassles on the handlebars ) .

You might want to tell Nick Sanders that....

Given that the 200 inch Palomar is driven by a motor with about the power of a domestic hairdrier I doubt that the difference between a Harley and a 200 bhp XXR FireSquirt is that important in considering belt drives in astronomy! As for riding around the world with chain drive, you obviously can. I did a 7000 mile tour on a chain drive myself. You can also push a peanut to the top of Pike's Peak with your nose... if you really want to! Google isn't playing for me but check it out!

(Nice to hear that Nick Sanders is still going, though. He was around in 'my day' as well.)

Olly

[vdb]

Soon I'll be able to jump in with Avalon experience I hope ...

For me no more worm drives, period ... even my IEQ45 that seems to have had zero backlash in the gearbox has developed some over the use of some lets say 10 objects ... grrrr ....

I'm kicking myself for not buying the flipless design but didn't want to take risks ...

If weather will permit I will have a first run tomorrow or the day after ... it's very portable and that is why it is complementing the mesu 200 ...

As Olly already mentioned there is nothing in that weight/zero backlash/low pe category ...

The tandem setup although not working was obscene wide with a momentum arm that was huge and it didn't waiver a second.

(reason it failed was imaging at the same time with 2 totally different scopes makes one "rotate" around the one that is being guided, I guess polar allignment needs to be spot on and the optical axis's need to be aligned to make that work )

Someone who wan't remote operation, wait for the new updates or uses another goto system ...

Yves

[Earl]

Id be very interested in what you have to say Yves