39 replies to this topic

[prsnikt]

So I am married to my EQ : a classic CEM25P; not divorcing this one, what with all the costs effort learning lost sleep and back pain.

 

Now the optics side of the family may be growing, and I thought maybe should also look at the newer generation of gadgets.  Not so much the payload capacity (since this time it's a reverse process) but the technology capabilities.  Some reasonably priced examples:

HAE16

HEM27

Juwei17

 

I have read here and there and even some on CN, though just like the guide scopes thread it would be nice to have a town hall on these newer gadgets, especially for the newer hobbyists.

To start, the much lighter weight of the mount itself is the first accolade, and perhaps even counterweight optional!  That's a no brainer.
Next, the "hybrid" approach seems to take advantage of the strain wave for RA, belt/worm for DEC, and supposedly leave the issues behind for the respective axes.  My knee jerk query was ... really?

Edited by prsnikt, 16 February 2025 - 04:21 AM.

[Kevin_A]

Personally coming from iOptron Gems and IEQs, I would skip the hybrids all together and go to a HAE18 or HAE27 or AM3/5. Why bother with balancing Dec anymore and some iOptrons always had deck backlash issues including my Gem28 . I have a AM5 now and the only way I would go back was if my mount was going in an observatory and then I might go with a Cem70.

[prsnikt]

@Kevin_A

So you sold your iOptrons huh?  Gosh this AM5 better be the cat's meow.
Come to think of it ... I recall reading about a 3D printed harmonic drive head when I was scanning for 3DP tech ... pretty neat project.  I suppose I could con some of my "pals" to let me use their metal deposition systems to cook one up, and dump in a couple honkin nema23 hi res steppers?    Yeah that will be the day.

Anyway in your experience the strain wave works fine for DEC.  So what's the deal with all the user "backlash" on that?  (pun totally intended!)  Perhaps it's just an algorithm issue, since many are still based on dealing with traditional mechanics?

[Kevin_A]

Yes, i sold my all my iOptrons but wish i has kept the ieq45 pro as it was nice, but very heavy to drag in and out. The issue with the cem26/gem28 backlash issue all came down to bad factory setup of the dec shaft bearing preload and they also had no QC on the mesh plunger spring pressure. IOptron ended up sending out a few softer mesh plungers and having them all tested due to various spring pressures. They created a PDF for users to adjust the Dec bearing preload but many users were not that inclined. So basically lots of people got great mounts and quite a few got badly setup ones. The best thing about strainwave gears on both axis is no problens with mesh or backlash and no worry about perfect balance, no worry about screwing up worm threads by accident and lastly… the mounts are fly weight! Win, win, win!

[Celerondon]

So I am married to my EQ : a classic CEM25P; not divorcing this one, what with all the costs effort learning lost sleep and back pain.

IOptronCEM25P.jpg

 

Now the optics side of the family may be growing, and I thought maybe should also look at the newer generation of gadgets.  Not so much the payload capacity (since this time it's a reverse process) but the technology capabilities.  Some reasonably priced examples:

HAE16

IOptronHAE16.jpg

HEM27

IOptronHEM27.jpg

Juwei17

Juwei17.jpg

 

I have read here and there and even some on CN, though just like the guide scopes thread it would be nice to have a town hall on these newer gadgets, especially for the newer hobbyists.

To start, the much lighter weight of the mount itself is the first accolade, and perhaps even counterweight optional!  That's a no brainer.
Next, the "hybrid" approach seems to take advantage of the strain wave for RA, belt/worm for DEC, and supposedly leave the issues behind for the respective axes.  My knee jerk query was ... really?

That town hall might not draw much interest since strain wave mounts are practically old news. Searching of Cloudy Nights threads from past years or strain wave mount reviews on YouTube shows that the big questions have been asked and answered many times over.

 

iOptron may have been motivated to market hybrid drive mounts due to cost considerations or a slight reduction in weight and bulk. This seems likely because, as Kevin A noted, using a worm drive on the DEC axis offers no performance advantage over a strain wave drive—aside from those two benefits.

 

The counterweight issue is intriguing. Without a counterweight, the AM5 can outperform the more massive HEQ5 in payload capacity and match or even exceed its performance. With a counterweight, the ZWO strain wave mount rivals the similarly priced EQ6-R Pro—even though the AM5 itself weighs barely more than a single EQ6-R Pro counterweight! (AM5: 12 lbs). For reference, an EQ6-R Pro mount head weighs 38 lbs and this massive mount is sold with two 11-lb counterweights. (60 lbs!) 

 

Beyond their compact size, lightweight design, and consistent guided performance, strain wave mounts offer another key advantage: simplicity. Other than software settings, a full strain wave drive mount requires no tweaking, tuning, or adjustments to function properly—none are even possible. Compare that to worm drive mounts, which sometimes require tuning even when brand new!

 

Don

 

 

          Vixen GP                         ZWO AM5

     15.4 lbs capacity              44 lbs capacity 

 

Edited by Celerondon, 18 February 2025 - 07:39 PM.

[Jared]

If weight and size aren't an issue? I would stick with a traditional GEM. Much less expensive for a given level of capacity and tracking accuracy. If weight and size are considerations? Harmonic drive mounts are great, but they don't generally track as accurately as a similarly priced GEM. I agree with Kevin_A that the hybrids don't seem all that beneficial unless you are struggling to afford a harmonic drive and really care about the weight. They can save a little money, but I'd rather not have to worry about declination backlash.

[prsnikt]

@Celerondon

Indeed there are some threads out there ... though I hope more information can still surface with new minds seeing things from different angles.  Harmonic drives for hobby astronomy only seem to go back a few years?  I am considering a strain box, though some folks would like to dig a little deeper than what's already been evaluated.

Good example ... ZWO themselves criticize the term "periodic" in PEC when applied to harmonic drives ( data reminds me of chaotic spectral and power conditions for very high power modelocked lasers which create intracavity saturation intensity management problems which means boom! if not careful )

 

So for moderate exposure times which supposedly can be dealt with by known PEC data and no guiding, it seems these high torque drives will need guiding for that, and then guide cadence can be increased to compensate but then weak guide stars create definition problems etc etc.  Anyway, always a compromise in engineered products, that fine, that's how it goes.  Then of course we all hail the low mass setup, but then we string a tri-hammock and put rocks and batteries to weight things down for stability and wind resistance.  So it's back to the 6 or half dozen hand waving.  But still OK, it's just redistributing the components within the total energy manifold for an effort.

However, there should be ways to develop new algorithms to counter these chaotic signatures?  I know back propagation neural nets may not work here (as even I found a counterexample that would diverge the equations).  Good lord we can look at feed forward, convolutional, recurrent, etc though that's still just a bunch of equations going in circles, not to mention how chaotic the training would be just to get baseline coefficients.  Chat and Deep simply explode.  Field ops just say more guiding.  Well ... I am hoping some genius sees this problem and tosses us mortals a bone.
 

And of course a practical accolade -- Eq and Alt/Az dual mode operation, don't need a fork just a wedge.  All these newer toys are pretty cool.

[prsnikt]

@Jared

Yes that's the thing ... especially for a newbie with shallow pockets but deep curiosity, the almighty $ comes into play. 
Pity the Rainbow's are a premium.  Certainly a great secondary revenue channel for a robotics company making the drives anyway.  Come to think of it ... The Rainbow AstroMaid or AstroButler robo would be the next big thing : it will set up your rig for you just the way you like it down to the positioning precision you define.

[Ardsley Astro]

I like my HEM15 Hybrid strain wave, I do have a niggle with an RA oscillation that I'm trying to resolve but overall I'm happy with it. One thing I think that gets overlooked when it comes to payload, is with strain wave mounts the thing to watch is the moment arm. The described payload limit is only correct when the centre of mass of that payload is 200mm from the centre of the RA axis. This includes the distance from saddle to the RA axis. The Hybrid mounts have an advantage here as the saddle is a lot closer to the RA axis than on full strain wave mounts. I think I measured on my HEM15 from the centre of the RA axis to the saddle to be around 70mm. I'm pretty sure I've read that the AM5 for instance that distance is over 100mm.

 

In effect what this means is the further out the centre off mass past 200mm the lower the payload limit gets. But the opposite also applies. If you can get the payload centre of mass closer to the RA axis the payload limit increases. 

[chvvkumar]

I went from CEM26 to AM5N, now I am getting another AM5.

 

[Dave Novoselsky]

How do the new SW Wave mounts figure in here in comparison to what seems to be the consensus in favor of the ZWO?

[sw196060]

how are these strainwave mounts for GoTo and plain tracking for visual?

 

I like how compact they are and can be used without a counterweight.

Edited by sw196060, 19 February 2025 - 01:08 PM.

[chvvkumar]

how are these strainwave mounts for GoTo and plain tracking for visual?

 

I like how compact they are and can be used without a counterweight.

I have not used mine without software but goto is super accurate if polar alignment is good. I get my PA within 1 arc-min error and can reliably get Jupiter in the center of my frame with an effective FoV of 0.83° with ~800mm focal length refractor, ASI533 camera and SharpCap's go to.

Edited by chvvkumar, 19 February 2025 - 01:28 PM.

[sctchun]

how are these strainwave mounts for GoTo and plain tracking for visual?

 

I like how compact they are and can be used without a counterweight.

I cheat like mad when doing visual, I have a finder scope with a camera on top of my rig with an X-Y adjuster and align that to my eyepiece.  From there I use ASIair to point to stuff in the sky.  I use my mount in EQ mode and I try to polar align it when possible.  Awesome for outreach.

 

For my AM5, I can go up to my 107mm.  From there anything bigger I use a 5kg counterweight.

Edited by sctchun, 19 February 2025 - 08:12 PM.

[WadeH237]

Indeed there are some threads out there ... though I hope more information can still surface with new minds seeing things from different angles.  Harmonic drives for hobby astronomy only seem to go back a few years?  I am considering a strain box, though some folks would like to dig a little deeper than what's already been evaluated.

Do you have some specific questions?

 

There's nothing mysterious about strain wave mounts.  The drive technology goes back almost seven decades.  Even for astronomy use, there have been strain wave mounts for about 20 years.

 

What changed recently is the availability of lower cost options.  Before ZWO broke into the market, the Rainbow Astro and Hobym Crux mounts.  And before that, going back to the mid-2000's, there were mounts from a company called Chronos.

 

The information may not be nicely packaged in one place, but if you ask specific questions, folks here can probably answer them.

 

If you are mainly curious about how strain wave drives actually work, I like the Wikipedia article on them.  It even includes a cool animation of what they look like internally when operating.

[prsnikt]

@WadeH237

Oh my goodness I am so far on the outside it isn't funny.  Just a little history:

First there were all the cheapie Xmas present class "telescopes" from uncles and aunts ... some actually had those remote wire controls and a pretty stable tripods.  By 10 I had half a dozen, heck of a good "spy" scopes ... 8-)
Then came the SLR camera, tripod, and a zoom lens ... I mean that setup was not bad for it's time back in the early 70's, if I recall it was like a 1000mm Nikkor telephoto (recall that old term?) which if I dinged I would have been buried alive cuz an aunt got it straight from Japan and lugged it through customs.  Loved that woman.
Finally I got the bug and could afford the fork mounted Powerstar PEC from Oceanside Photo & Telescope (now that was a store back in the day!) and still have it.  Of course I didn't even realize anything about that meridian flip (say what?) using that fork.  Could have bought a small house with all the extra optics I gathered up over the years.  For one eyepiece I could get a reman 3 litre V6 for crying out loud.  Though I am a photonics professional so I get the costs.

More recently was the iOptron mount and so now here I am ... and you guessed it ... it took an article about 3D printing some "harmonic mount" that opened my blind eyes to these "strain wave" boxes.  And yes I knew about strain waves for other engineering projects, it just took that article and then seeing how small and low(er) cost they are in modern days such that they become a viable product for hobbyists.

 

So the high level details that sticks out are: low backlash, forget about any kind of PEC, costs more for similar guiding, much lighter, dual mode.  The AM5 seems to be the "workhouse" and has enough options on it.
Though that Juwei17 is the parallel knock off and folks seem to like the open source management ... but no homing right?

[mrlovt]

I cheat like mad when doing visual, I have a finder scope with a camera on top of my rig with an X-Y adjuster and align that to my eyepiece.  From there I use ASIair to point to stuff in the sky.  

That's cheating?  That's not cheating, it's efficient! 

[Celerondon]

@WadeH237

Oh my goodness I am so far on the outside it isn't funny.  Just a little history:

First there were all the cheapie Xmas present class "telescopes" from uncles and aunts ... some actually had those remote wire controls and a pretty stable tripods.  By 10 I had half a dozen, heck of a good "spy" scopes ... 8-)
Then came the SLR camera, tripod, and a zoom lens ... I mean that setup was not bad for it's time back in the early 70's, if I recall it was like a 1000mm Nikkor telephoto (recall that old term?) which if I dinged I would have been buried alive cuz an aunt got it straight from Japan and lugged it through customs.  Loved that woman.
Finally I got the bug and could afford the fork mounted Powerstar PEC from Oceanside Photo & Telescope (now that was a store back in the day!) and still have it.  Of course I didn't even realize anything about that meridian flip (say what?) using that fork.  Could have bought a small house with all the extra optics I gathered up over the years.  For one eyepiece I could get a reman 3 litre V6 for crying out loud.  Though I am a photonics professional so I get the costs.

More recently was the iOptron mount and so now here I am ... and you guessed it ... it took an article about 3D printing some "harmonic mount" that opened my blind eyes to these "strain wave" boxes.  And yes I knew about strain waves for other engineering projects, it just took that article and then seeing how small and low(er) cost they are in modern days such that they become a viable product for hobbyists.

 

So the high level details that sticks out are: low backlash, forget about any kind of PEC, costs more for similar guiding, much lighter, dual mode.  The AM5 seems to be the "workhouse" and has enough options on it.
Though that Juwei17 is the parallel knock off and folks seem to like the open source management ... but no homing right?

That is an interesting question, OP.  The AM5 and AM3 do have homing features.  Don’t the OnStep controlled mounts also have this capability?  
 

Don

 

Homing button in action. 

[Celerondon]

@WadeH237

Oh my goodness I am so far on the outside it isn't funny.  Just a little history:

First there were all the cheapie Xmas present class "telescopes" from uncles and aunts ... some actually had those remote wire controls and a pretty stable tripods.  By 10 I had half a dozen, heck of a good "spy" scopes ... 8-)
Then came the SLR camera, tripod, and a zoom lens ... I mean that setup was not bad for it's time back in the early 70's, if I recall it was like a 1000mm Nikkor telephoto (recall that old term?) which if I dinged I would have been buried alive cuz an aunt got it straight from Japan and lugged it through customs.  Loved that woman.
Finally I got the bug and could afford the fork mounted Powerstar PEC from Oceanside Photo & Telescope (now that was a store back in the day!) and still have it.  Of course I didn't even realize anything about that meridian flip (say what?) using that fork.  Could have bought a small house with all the extra optics I gathered up over the years.  For one eyepiece I could get a reman 3 litre V6 for crying out loud.  Though I am a photonics professional so I get the costs.

More recently was the iOptron mount and so now here I am ... and you guessed it ... it took an article about 3D printing some "harmonic mount" that opened my blind eyes to these "strain wave" boxes.  And yes I knew about strain waves for other engineering projects, it just took that article and then seeing how small and low(er) cost they are in modern days such that they become a viable product for hobbyists.

 

So the high level details that sticks out are: low backlash, forget about any kind of PEC, costs more for similar guiding, much lighter, dual mode.  The AM5 seems to be the "workhouse" and has enough options on it.
Though that Juwei17 is the parallel knock off and folks seem to like the open source management ... but no homing right?

Apparently this is correct, OP.  Who knew that the (just as good?) knockoff lacked a basic feature of the AM5?  
 

Don

[prsnikt]

@Celerondon
Thank you for confirming ... the lower cost does come with lower functionality, pity.  However those are steppers and therefore position determinant and at 1.8deg that's like mod200 so I presume a little code for a clock counter and status register could theoretically create a "home" position and a little coin battery could preserve the data in real time.  Come to think of it some of us old goons used an obscure thing called Lazarus to do something very similar for a 6x stepper based articulation rig in a high e-12 vacuum chamber so we can know exactly where we stopped doing something from day to day.
The impression I get from the Juwei camp is those are good for "tinkering" and "updating" ... not necessarily for the faint of heart though I presume many of us are tinkerers with some serious gear in our caves so no worries there
However spending some not so cheap coin on a gadget then opening it up to upgrade the steppers and driver boards may achieve a goal which items like the AM5 and similar may have already accomplished and most probably at a comparable cost plus a warranty and some support to go with it.
Now that 3D printed home brewed harmonic head is a different story 
 

[Celerondon]

I cheat like mad when doing visual, I have a finder scope with a camera on top of my rig with an X-Y adjuster and align that to my eyepiece.  From there I use ASIair to point to stuff in the sky.  I use my mount in EQ mode and I try to polar align it when possible.  Awesome for outreach.

 

For my AM5, I can go up to my 107mm.  From there anything bigger I use a 5kg counterweight.

This ring style guide scope mount allows a similar adjustment.  

 

With the ASIAIR controlling things, the AM5 in EQ mode, and a single USB cable running to the guide (main) camera, each polar alignment and GoTo activity is plate solved so each action is easy and accurate. 
 

Like Steven, I find this system so convenient that it feels like cheating.  Although some protest about the extra equipment and cabling required, the ASIAIR is a tiny box with wireless capabilities and many of us are already accustomed to mounting and using some sort of finder. 

 

Don

 

Edited by Celerondon, 01 March 2025 - 08:36 AM.

[Alioli]

Personally coming from iOptron Gems and IEQs, I would skip the hybrids all together and go to a HAE18 or HAE27 or AM3/5. Why bother with balancing Dec anymore and some iOptrons always had deck backlash issues including my Gem28 .

Do you think it would have trouble on dec with a small scope like an RC51? Currently considering getting the HAE16 but now wondering if the extra SW is worth the extra $150

[Celerondon]

Do you think it would have trouble on dec with a small scope like an RC51? Currently considering getting the HAE16 but now wondering if the extra SW is worth the extra $150

I agree with Kevin, so my answer would be a definite yes. 

 

If you can afford the $150 it is certainly worth it.  The extra cost is a reasonable expense when you consider that your mount will have no worm gears to worry about and no precision balancing requirements.  Every month there are new threads on Cloudy Nights and other sites addressing worm adjustments, tight axes, and balance adjustments.  People even open new or nearly new mounts to free them up for balancing.  None of these strain wave drive mounts require any routine adjustments.  The only user adjustable components inside are the belts and so far, those things have not stretched enough to require periodic tightening on any strain wave mount that I know of.

 

Don

[BucketDave]

Well, my two penn'orth (imperial version of your 2 cents) is that I am perfectly happy with the hybrid concept. Balancing takes less than a minute, the mechanism is lighter and cheaper than strain-wave and it regularly guides in DEC to around 0.5".

Using a SW gear for DEC is just over-designing the system - I just don't see a compelling reason to do so for these small portable mounts.

[prsnikt]

@bucketdave

i mess with my pals by giving them my 2 shillings worth     more pence than they can handle!

the sw units seem to avoid the backlash issue though dont have the usual pec ... however even for the standard gearboxes i suppose one could plan ahead and "carefully" drive everything in one direction (so will need to teach the system to tweak in nonlinear amounts rather than just standard fixed increments to avoid overshoot, with the benefit of known pec, tightened belts, etc etc etc)

fun hobby!