Buying a Strain Wave Mount? You Have Options

Story


If you’re new to astrophotography, one of the first pieces of equipment you will need to purchase is an equatorial telescope mount. Whether that happens to be a portable star tracker or a heavy-duty equatorial platform capable of carrying a large telescope, tracking the night sky is an essential part of astrophotography.

Your telescope mount serves as the cornerstone of your astrophotography setup. It is responsible for accurately following the apparent motion of the night sky and facilitating the capture of prolonged exposure images.

Investing in a high-quality astrophotography mount is critical. Thankfully, in 2024, there are some fantastic options to choose from, including a new type of technology known as ‘strain wave drive‘ or ‘strain wave gearing.’

I recently polled the AstroBackyard Facebook group to see which telescope mounts they are currently using for astrophotography. I am amazed at how many people have switched to a strain wave drive mount, specifically the ZWO AM5.

It’s About Convenience and Reliability

While I know that the telescope manufacturers like to boast about the incredible tracking performance and advanced functions of their high-end mounts, the average user just wants a product that is quick to set up and works seamlessly without headaches. 

The nature of a hobby that requires a clear night sky means that you need to ‘react to weather,’ and a clear night doesn’t always occur at a convenient time. An astrophotography mount that allows you to get up and running quickly and accurately means more imaging time. 

While I still use my Sky-Watcher EQ6-R Pro for plenty of astrophotography projects throughout the year, the ZWO AM5 comes out of the garage more often. I can polar align the mount quickly using the ASIAIR electronically assisted polar alignment feature and be on my way.

ZWO AM5 Mount

The ZWO AM5 strain wave drive equatorial mount.

The small form factor and lack of a counterweight (for loads under 28 pounds) mean that this thing can travel. In fact, I have traveled to Oklahoma (Okie-Tex Star Party) and Florida (Winter Star Party) with my AM5 nestled safely in my personal item bag on an airplane. 

I understand that users of larger telescope systems will require a larger equatorial telescope mount with counterweights. But for compact refractor-lovers like myself, a strain wave drive mount like this is the perfect option at home and on the road.

Amateur astrophotographers are quite comfortable with autoguiding their systems, so this necessary step for precise tracking is not an issue. As long as the tripod base underneath the strain wave drive mount is stable and secure, you can enjoy counterweightless astrophotography. 

More Strain Wave Drive Mounts

While it’s clear that the vast majority of the amateur astrophotography community has welcomed the ZWO AM5 with open arms, others do not like the closed-ecosystem nature of ZWO products, and I get that. The ZWO AM5 is not the only strain wave or harmonic drive equatorial telescope mount on the market. 

iOptron, Pegasus Astro, Sky-Watcher, and more companies have introduced strain wave drive mounts. The iOptron HAE29 goes head-to-head with the ZWO AM5, offering a 28-pound maximum payload capacity in a package weighing only 8 pounds. You can control this strain wave mount using image capture software like N.I.N.A. on a mini PC or laptop if you’re not a fan of the ASIAIR experience. 

 

strain wave mountsstrain wave mounts

Strain Wave Drive Mounts from iOptron, Sky-Watcher, and Pegasus Astro.

The Pegasus Astro NYX-101 is in a class above the ZWO AM5 in terms of maximum payload capacity (44 pounds) but also has a higher price tag than the AM5 and comparable mounts. iOptron has their own option in this class, too, the iOptron HAE43EC Strain Wave AZ/EQ mount.

Sky-Watcher Wave 100i and Wave 150i Strain Wave Mounts

Sky-Watcher recently announced their new line of strain wave drive mounts, the Wave 100i and Wave 150i. These units leverage the same technology and add a few handy new features, including the ability to unlock the clutches in RA and DEC. 

The Sky-Watcher Wave 100i and Wave 150i feature stepper motors and a 300:1 reduction ratio strain wave gear, just like the ZWO AM3 and AM5. Both models include ports for controlling the mount using your existing Sky-Watcher SynScan hand controller or via your PC using EQMOD or the ASIAIR. 

The Sky-Watcher Wave 100i is currently priced at  $1695 USD, slightly more expensive than the comparable ZWO AM3 ($1499 USD). It weighs slightly more than the AM3 (9.5 lbs) but can handle a heavier payload of about 22 pounds without a counterweight. 

Sky-Watcher Wave 150iSky-Watcher Wave 150i

The Sky-Watcher Wave 150i Strain Wave Drive Mount showcased at NEAIC/NEAF.

For those who need something a little more capable, the Sky-Watcher Wave150i is priced at $2,195 USD. This sits just above the price tag of both the ZWO AM5 and the iOptron HAE29. With this higher price tag comes the highest maximum payload capacity in this category of strain wave mounts (33 pounds without a counterweight).  

As a fan of the Sky-Watcher brand (and the people behind it), I was glad to see them adopt the new technology to avoid falling behind market demand. I am sure the Sky-Watcher Wave 150i will be a big seller in 2024, and I look forward to trying one out myself when it is released. 

I had a chance to see the Wave 150i in action at the North East Astro Imaging Conference in April 2024, and it looks like a winner to me. I think that many existing Sky-Watcher EQ6-R Pro owners will end up making the switch to this model when they are ready. 

As you can see in the photo below, it had no trouble handling the large Sky-Watcher Quattro 150P Newtonian optical tube while mounted on a carbon fiber tripod. 

Sky-Watcher Wave 150iSky-Watcher Wave 150i

The Sky-Watcher Wave 150i with a Quattro 150P Newtonian Reflector mounted to it. 

Limitations and Best Use Cases

Strain wave mounts do not use worm gears like traditional equatorial mounts. They are unique in that they can operate without counterweights while still supporting moderately sized telescopes.

Another benefit to strain wave drive mounts is that they have zero backlash. However, they do suffer from some periodic error, which will need to be corrected using autoguiding. 

The ZWO AM5 documentation lists a maximum practical focal length of 900mm for deep-sky astrophotography, although I have not heard much about this limitation in the real world.

I regularly use the ZWO AM5 strain wave mount for deep-sky imaging using telescopes in the 250-800mm range. The following photo of the Triangulum Galaxy was captured using the ZWO AM5 and 115mm APO refractor telescope.

Triangulum GalaxyTriangulum Galaxy

The Triangulum Galaxy captured using a 115mm refractor telescope on the ZWO AM5.

The transition from traditional German equatorial mounts to strain wave mounts reminds me of when astrophotographers went from CCD cameras to CMOS. The technology is evolving, and some folks are more welcoming of it than others. 

Final Thoughts

While I don’t feel there is an immediate need to upgrade your German equatorial mount to a strain wave design, the astronomy equipment manufacturers are clearly ‘all-in’ on this new technology. 

The strain wave design has clear advantages in terms of portability, set-up time, and ease of use, making it an attractive option for those looking to upgrade their telescope mount or invest in one for the very first time. 

I have personally had a great experience using the ZWO AM3 and AM5 mounts with my astrophotography telescopes and have taken some great images with them. I now find myself recommending an AM5 over a traditional EQ mount to beginners asking for advice. 

Have you experienced a strain wave drive mount yet? Let me know what you think in the comments.

Dark Skies at the Winter Star PartyDark Skies at the Winter Star Party


 

Trevor Jones is a deep-sky astrophotographer and a valued member of the RASC. His passion is to inspire others to start their astrophotography journey on his YouTube Channel, so they can appreciate the night sky as much as he does. His images have been featured in astronomy books and online publications, including the NASA Astronomy Picture of the Day (APOD).

Helpful Resources:

Leave a Comment