Avalon Linear mount review

[Jarno_c]

Hi all, I've been lurking here for the last couple of years. A long time ago I promised to post a review of the Avalon Linear mount and I've finally gotten around to it, so here goes.

The good

First, a little background. The Avalon Linear is an equatorial mount which doesn't use any gears, instead it's completely based on belts and pulleys. The rationale behind this is that while it won't necessarily reduce periodic error, it'll make it much smoother and more gradual so it can easily be guided out. The belts also are completely free of backlash and don't require lubrication of maintenance.

Mechanical

The mount head itself is completely made of machined aluminum with very tight tolerances, there are barely any gaps between the parts. The head is attached to the tripod with two screws which unfortunately aren't captive, which means you have to hold the mount head with one hand while putting in the screws with the other. This is made easier by the handle conveniently placed over the center of gravity but I'd still have like those screws to be captive. The mount electronics are all suspended underneath the RA axis so they act as a counterweight. This means you can use less actual weights but the downside is that all the connections move as the mount slews around the sky. Speaking of counterweights, those are stainless steel of the same finely machined quality as the mount head. The counterweight rod is another hefty 30mm thick piece of stainless steel which is inserted into the mount head and then held in place with a screw that falls into a safety slot. As long as you don't have too many counterweights on it, you can leave them on and attach and remove the counterweights as a single assembly. It's one of several things that makes setup faster and easier than with other mounts. The saddle clamp is another machined part (I don't think there are any castings anywhere on this mount) and it fits Losmandy type plates. It has a single clamping screw and personally I'd have preferred two, but it holds even heavy OTA's securely enough. There are several types of polar scopes in circulation, mine is apparently the same one Synta uses but I can't confirm that since I've never used or owned a Synta mount. It seems functional enough but I've never actually used it since I prefer to use a Polemaster and later the Asiair to polar align. And finally, the alt-az adjustment screws. These have knurled knobs which are easy to grip even with thick gloves on. Movement is smooth so the mount can be polar aligned very precisely. This is what it looks like, all set up:

Drive and electronics

Avalon mounts can be provided either with the Synscan system, or Avalons own StarGO system. The main difference is that where Synscan is mostly a standalone system, the StarGO requires an external device like a laptop or tablet to run its software. I chose the StarGO since I'd be bringing along a laptop for guiding and camera control anyway. The mount by itself has little to no "intelligence" built in: you can slew it, you can control a Baader Steeldrive focuser and that's pretty much it. There's no goto, no PEC, no platesolving, no polar alignment routine, nothing. All that is handled by the StarGO software which is very intuitive to use although the first versions were a bit on the basic side. I understand it now includes things like a polar alignment routine and plate solving but back then it didn't, and I've switched to an Asiair since then. Since I no longer use the Avalon software I can't really comment on how it performs nowadays. Goto's were executed smoothly and in 90% of the cases placed the target near the center of the FOV. In the remainder of the cases the target was off to the side but it never was completely outside the FOV. A sidenote here is that the mount doesn't have encoders so goto accuracy is highly dependent on how accurately the mount is polar aligned and placed in the home position. There are laser engraved markings on the mount to help with this. Because of the belt drives the mount is very quiet. You can hear a soft whine from the motors when they're at full speed but it's hardly audible two meters away and won't wake the neighbors even in the quietest places. For those interested, the mount used a four-step reduction system. The first three steps use opaque yellow belts which aren't tensioned, the fourth and final step is a much larger translucent belt which has a tensioning mechanism. All this will become relevant later. Here's an overview of the mechanism with the steps color-coded:

I've heard from others that the belt mechanism is more sensitive to wind but I've not noticed that myself. Usually when the wind picks up at my observing site, it's strong enough to cause problems for all but the very heaviest mounts. Weaker gusts are immediately compensated for since the mechanism is indeed almost free of backlash and guiding can be set pretty aggressively. The stars may become a bit bigger but it's rare to have any trails. Overall I would say the mount is well suited to mobile astrophotographers. It's very easy to set up and tear down, and tracks and guides very well. Or at least it used to...

The bad

On my last couple of sessions I noticed that guiding in RA was worse than in DEC and sometimes would go completely off-track. Since I'm using an Asiair to control the mount, and this has its fair share of software issues, I didn't think much of it. I usually returned the mount to its home position, reset the Asiair and all was well again. But two days ago it happened again and this time, when I sent the mount to the home position it started making loud grinding noises. I immediately stopped the slew and noticed there was a lot of play in the RA axis. I called it a night and when I opened up the mount the next morning a handful of debris came falling out, much to my shock and surprise. As it turns out one of the belts has completely disintegrated. The reinforcing wires are still intact but the polymer around it is just crumbling away:

I inspected the other belts and those are showing cracks and damage as well:

[

Obviously this shouldn't be happening with a mount that's just over 5 years old so I contacted Avalon.

The ugly

I informed Avalon of what had happened and included photos of the destroyed and damaged belts. Their reply was that the mount would have to be returned to Italy and then they would give me an estimate of the repair costs. This surprised me because obviously there's a production fault with these belts since only the yellow opaque belts are affected and the larger transparent belts are just fine. I asked another Avalon user to inspect the belts on his mount and he's seeing cracks in the belts as well so it's not something unique to my mount, or caused by something I did. This is not what you'd expect from a mount in this price range. I told Avalon as much and they agreed to send me replacement belts for 98 euros per axis, excluding VAT and shipping. I'd already looked up the belt manufacturer and this type of belt costs less than 10 euros! So total cost for both axes would be around 60 euros while Avalon wants to charge over 200, and for something that should never have happened in the first place. I don't expect them to send the belts for free, the mount is out of warranty after all, but in my opinion the proper response would've been "Apologies, this isn't the quality you should expect from us and we're sending replacement belts at cost + shipping." I mentioned that another user has also seen cracks in the belts, he made a movie of the belt moving so you can see what's happening for yourself and judge if this is normal for a mount costing over 5K:

https://youtu.be/OF7oVwpDk4w

While I still like the mount I'm extremely disappointed with Avalons customer service. I'd recommend that all Avalon owners regularly check their mounts belts and at the first sign of cracks, notify Avalon immediately.

Jarno

 

Edited September 25, 2021 by Jarno_c

[Dr_Ju_ju]

If you are having problems sourcing belts, then have a look here https://www.beltingonline.com/  they do belts for almost all applications & system types etc., at reasonable cost, quick shipping etc.

I've just used them to source some belts for a Baader Steeltrack focuser, which uses a 3mm pitch belt, I ordered Thursday late afternoon & they turned up in the post this morning....

[Jarno_c]

Thank you Julian, finding replacement belts will not be a problem. They're standard industry belts with MXL profile and they cost next to nothing, which is why Avalon's attitude annoys me so much. I'm just debating whether to go for glass fiber or steel reinforced belts. In theory the steel belts should have less flex but the elasticity of the reinforcing material is probably an order of magnitude less than the polyurethane teeth, so I doubt it makes a difference.

Jarno

[Froeng]

Hi Jarno,

what a shocking find and terrible service! They advertise the mount as completely maintenance free!

This is indeed disappointing. I am sorry for you.

I have the Linear on my list as one of the options of a “final mount” maybe I should reconsider this… 😞 A shame as I really like the looks and the concept.

Edited September 25, 2021 by Froeng

[newbie alert]

Sorry to hear of your recent mount dysfunction, I've never heard of a Avalon mount having issues, like the above comment it's said that  it's maintenance free... The one thing that flagged up in my mind is that belts that look like they've self destruct like yours has are over tensioned so just replacing the belt might not work, granted it's taken 5 years to show it's fault but a readjustment  on that  axis is worth looking into..

I'm with you sharing that bitter pill, I once had to buy a whole new motor on a cgem because the housing on the stepper motor wasn't tightened and had worked itself loose causing the first cog in the gearbox to flatten 2 teeth..The ever helpful celestron said it was a pier collision, ( which never was true) so along with other celestron products I've had issues with I doubt I'd by that brand ever again

Hope you get it sorted

[JeremyS]

Ouch! Really sorry to hear your experience with the Avalon mount.

[Xsubmariner]

Wow, what a disappointing response you received from Avalon.  Having owned an M-UNO, I was considering upgrading my current mobile mount (NEQ6) to a Linear at some point. Your experience has focused my thoughts .

[Skipper Billy]

I had one for a couple of years and was very impressed with it.

The takeaway things for me with it were....

When its windy you can see some 'bounce' on the guiding graph as the belts stretch ever so slightly in the gusts then return to normal.

The images always look far better than the guide graph suggest they might

The mount likes short sharp guide adjustments rather than long guide exposures to even out the seeing

Its beautifully made and I had zero issues with it.

It's perhaps a little foolhardy of Avalon to advertise it as 'entirely maintenance free' - nothing is entirely maintenance free. The belts are cheap and easy to change.

Its a shame that such a good mount has been marred by poor after sales service.

 

[Jarno_c]

Update: Avalon has now confirmed there's indeed a small number of belts in circulation that do not comply with their specifications. Rather than steel reinforcements the manufacturer used Kevlar or something similar. I'm not sure this is indeed the root cause because that has now been confirmed to be hydrolysis: degradation of the polyurethane by coming into contact with moisture. The symptoms are cracking, an oily appearance and finally complete disintegration of the material. However if one part of the belts is not up to spec, the remainder might also not be. In case anyone is having problems caused by this wrong type of belt, Avalon will replace them free of charge, even if the mount is out of warranty. It took some prodding and pushing but eventually Avalon did (in my opinion) the right thing. I've received an email asking me to return the failed belts and if they're the faulty type (and they are, the wires indeed aren't metal) Avalon will send me replacement belts free of charge. Of course the weather gods will consider those belts to be new equipment and send in the mandatory three weeks of clouds, so I apologize in advance. 😉

Jarno

[ollypenrice]

The later stages of this post make better reading than the first because, in the early days, Avalon had a brilliant service reputation and the engineering of the mounts is lovely. I replaced mine only because a second hand Mesu became available and I recently bought a well-used Avalon for a new installation as well. I'll have to look at the belts on my used one!

To my mind the Avalon would be an obvious choice if the price new were lower but, as it is, it is far too close to the Mesu, which easily beats it on payload, precision and stiffness. Of course, the Mesu is also a lot bigger to move about. For its size I still like the Avalon, though, and agree with David that the guide trace doesn't seem to do justice to the real performance which really is very good.

Olly

Edited October 18, 2021 by ollypenrice

[AKB]

1 hour ago, ollypenrice said:

the Mesu is also a lot bigger to move about. For its size I still like the Avalon

This is a bit less of an issue with the new Mesu e200, as it’s a lot lighter.  I still like my Avalon M-Uno, though – no counterweights, no meridian flip – with the same belt drive arrangement as the Linear.  I haven’t checked the belts, but I’ve not seen any issue, so I’ll leave well alone.  I’ve also had great service from Avalon, because I shipped it back to them (pre-Brexit, thank the Lord) to get it upgraded to a dual Losmandy head.

Tony

[newbie alert]

Good to hear that things seem to be going in the right direction now

But assume that the belts with Kevlar in are super strong.. I'm sure that they use it in bulletproof vest and army helmets.. 

[900SL]

Speaking with my 'I do all my own Ducati servicing including the cambelts' hat on. I think 5 years + is pretty good for any polymer based belt system bent to small radii. 

Car systems typically last 7 years with service replacements at 5 years or 60,000 miles typically quoted.

The Avalon belts obviously won't be subject to anything like the stress or heat that an engine cambelt experiences, and they use different materials, but polymers tend to deteriorate over time and become brittle. Contact with solvents can drastically shorten the lifespan.

Good to see Avalon came to the table and offered a fix to the owner, and I would expect the belts to be a longer term maintenance item in general, and priced accordingly. 

   

[Jarno_c]

Well, Avalon indeed came to the table but not entirely voluntary. I sent them the defective belts and they confirmed they're the incorrect type. They then wanted to charge me for the shipping costs (at 3 times what it cost me to send the defective belts to them) and I really had to nag to get them to honor their promise . Their response here quite clearly says "In the case of a defect not due to misuse or natural wear, but, as in the case of non-compliant belts supplied to us by the manufacturer, the customer will not be charged of any cost, even if the repair exceeds the warranty period." We'll see if and when the replacements arrive, and perhaps these blasted clouds will finally have moved away by then...

Jarno

Edited November 28, 2021 by Jarno_c