Is the so called “60%” rule a thing for strainwave mounts ?

I’ve put considerably more load on many mounts than the manufacturers would recommend, and had great results too… Its all a matter of knowing your mount.. I used to image on an EQ6-R (this is 20 years ago now) with my imaging scope being a C11 XLT with a SBIG ST10XME + 8 position filter wheel and AO-8, and I used a William Optics Megrez 102 (102mm F/7 doublet APO) as my guide scope… All up, this was about 34kgs including a ADM dual losmandy saddle plate, camera equipment, scopes, dew heaters, dew shield etc etc. The mount was rated to 20kg. I used 5×5kg counterweights, always made the balance east heavy to maintain worm gear to worm wheel connection, tuned the worm/worm wheel meshing on both RA and Dec, belt driven, aftermarket bearings installed throughout and lubricated with a low temp teflon grease… The mount was extremely overloaded, but with very careful balancing and configuration I was able to have the mount operate just fine like that for a very long time. I’ve also had plenty of load on my harmonic mount, 120APO + 60mm APO with a full mono camera setup, computer, power box, dew control etc etc. without a counterweight… No issues at all.

I think with careful balancing you can certainly exceed the manufacture’s suggested max load. I think that most are being conservative in this area. I used to run a Meade lxd75 (remember those) for doing lunar imaging with a homemade 10 F/7.5 newt. the total payload was around 40 lbs. with very long moment arms. I couln’t do precision guiding with it but it never harmed the mount, i fact i still have it today.

If you think about it from an engineering point of view, if the load is balanced then the issue is really about moment arms, inertia and damping. A compact RC will be less troublesome than a long newt., even if the payload weight is the same.

Things might be a bit different with Harmonics though. It would be worth researching how these drives actually respond to out of spec loads. I suspect that it’s more of a problem with the reduction gears than the Harmonic dive itself.

Probably because a mount built from Legos and plywood is going to be good enough for visual.

Eric Gagné · May 23, 2026 at 07:34 PM

I really like my EQM-35 Pro but with the FLO pier extension on it it’s getting a bit heavy for me to carry in and out of the house so I’m thinking of getting a harmonic mount.

My rig weighs 13.6 pounds so I am wondering if it’s too close to the AM3N 17.6 pounds limit as I’d rather avoid using counterweights.

My first choice would be a NYX-88 if money was no object, other options might be a Wave 100.

So back to my question…..does the 60% generally considered as the max percent of capacity we should use apply to those mounts ?

I would say the 60% rule no longer applies to mounts, regardless of whether they are harmonic drive or conventional GEM’s with counterweights. That rule was really just a reaction to some manufacturers who tended to overstate their mount’s capabilities.

In the case of strain wave mounts, the weight capacity (without counterweights) is usually more about when the tripod gets to be too unstable to have confidence it won’t fall over in a strong wind or if lightly bumped. It’s less about the motors struggling to move the scope around at normal tracking rates. That’s just a generalization, but I think it’s still true.

That being said, strain wave mounts tend to have less accurate tracking than GEM’s with counterweights of similar capacity at a given price point. That’s simply the price of portability. Most people have adapted to this by using shorter/more frequent guide corrections which is perfectly workable if not quite optimal. Will the AM3N track accurately enough for your uses? Well, the manufacturer only guarantees ± 15” of PE which is a lot. Plenty of people manage to get that down under 1” with good guiding. I don’t know what focal length scope you are planning on mounting. If it’s just your 135mm, I’d say no problem at all. You said your rig weighs 13.6 pounds, though, so I suspect you are thinking of a different scope. What scope? How much aperture/sail area? How long a tube/moment arm? And how do you intend to guide the AM3N?

Jared Willson · May 25, 2026 at 02:13 AM

If it’s just your 135mm, I’d say no problem at all. You said your rig weighs 13.6 pounds, though, so I suspect you are thinking of a different scope. What scope? How much aperture/sail area? How long a tube/moment arm? And how do you intend to guide the AM3N?

The 135mm is sitting on a light pier at Starfront, I sold it a year ago. The one I’m talking about is an Askar 71F. It was a complicated setup that required adding a few things that added weight.

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TBH I am seriously leaning towards the NYX-88.

The SAL-33 would be a serious option if it wasn’t for the delay. I don’t want to wait 4 months.

The AM5N is a bad deal in my opinion, it costs more than the NYX-88, only has 1 more kg of capacity but I think it’s not in the same class as the Pegasus which I consider to be a premium mount.

And I don’t know what it is with the AM5N, maybe user errors but I have many topics on forums from people who have issues with guiding and that doesn’t inspire confidence

📷 IMG_4488.jpegNot a very good picture of my setup, but this is my 12” Meade SCT, weight 45lbs, on my AM5 mount with 20lbs of counterweights. Been using this setup for almost 2 years with no issues outside of vibration with a breeze, hence the windshields. I get .45 to .80 arcsecond guiding routinely with a guide scope, not an off axis guider. So as far as weight restrictions are concerned I think I broke the mold on that one. Oh and the 45lb is with the scope alone, not counting the camera, guide scope, crayford focuser and dew shield. So yeah a couple of extra pounds. I have numerous photos taken with this rig on my page, if any of you are interested in how well it does. The scope is over 30 years old, so not the best in coma, no HD and what not, but I’m not complaining. It flips and goes home all by itself with no issues. Took a minute to figure out were to put the counterweights but after that its been smooth sailing.

Disclaimer: This is how I do it, of course I would never recommend anyone doing what I’m doing at all, just showing it can be done. Your results may vary. This pushes the AM5 well past the weight restriction for sure. In my defense though, before I bought the mount I looked up the weight of my scope online. My scope was mounted originally on an LX200 fork mount, so before I bought the AM5 and de-forked my scope, I wanted to know what the weight was. Every where I looked they said the scope alone weighed in at 35 lbs, right at the max limit for the AM5 with all the attachments, so I purchased the mound and de-forked my scope. Then I weighed it by itself and found out all the info I had found was wrong, I thought well lets give it a try and after much trial and error I finally got it to work, and its been working ever since. Again I’m not saying anyone should do this, just that these mounts take way more than they are rated for.

I’m wondering, and it depends on your situation of course but I never take in my mount, just the OTA. My EQ6 just sits in the back garden with two trash bags over it. Been out there for two years in all weather, no issues.

I haven’t had an issue in Oklahoma but I suppose you could. That said, there are solutions involving covers and low voltage fans that should keep it from becoming an issue. Don’t forget, many of these mounts and scopes spend their entire lives an an observatory that’s unheated, uncooled and not humidity controlled. I really haven’t heard of any issues.

I have a AM5N which is 33lbs prior to counterweight as its “spec”.

I push well over 30lbs on this mount with my ASKAR130PHQ and hold perfect 0.2 guiding.

I would say no for the % rule like I use on my Celestron AVX

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I've read something that suggests the AM5 motors are buggy or weak.

I want to tell you about this.

A few days ago, I accidentally aimed the asiair at an object that hadn't yet risen, so the mount pushed into the wall of my balcony and, using the declination lever, lifted everything below it by about 2 cm. Then the safety clutch engaged and it stopped.

So, there were the following to lift:

- 10 kg of the 200/800 Newtonian telescope and the optical train;

- about 11 kg of the mount, extension, and counterweight;

- about 6 kg of that square structure underneath;

- 15 kg (3 cast iron disks) placed at the bottom as ballast.

As far as I'm concerned, instead of the NEMA17s, they could have easily used NMA14s; they still had plenty to spare.

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