In recent years, harmonic drive mounts have made a real splash in the astronomy market, ZWO’s AM3 and AM5 mounts being two well-known examples.
ZWO recently launched the second generation of its AM5, the AM5N harmonic equatorial mount, which promises higher load capacity and improved tracking and connectivity options over its predecessor.
We were naturally curious to see how this updated model compared.
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Unboxing
The ZWO AM5N arrived securely fitted in a solid foam carry case that holds the mount head, controller and cables, and provides space to fit the optional counterweight bar.
Finished in ZWO’s traditional red, the AM5N looked impressive and felt solidly built.
All adjusters and tighteners were made from machined aluminium and were sturdy yet easy to grip.
Also included is a hand controller, which is a great addition if you prefer that to using phone controls.
We noticed that the AM5N’s base has been redesigned, removing the azimuth locking knob seen on the AM5.
Other design improvements include better internal cabling to prevent chafing or twisting, reducing the risk of cables wearing down.
A pair of USB connectors have also been added, both of which allow mount control: a standard USB-B located on the mount body and a USB-C connection located on the back of the saddle.
Setting up the ZWO AM5N
We received the ZWO AM5N as a kit with a carbon-fibre tripod, but a mount-only option is also available.
One thing we noted was that when mounted on the tripod the combination is fairly short, at just over a metre tall.
While this shouldn’t pose an issue for astrophotographers, the optional tripod extension ZWO offers may come in handy for visual observers.
Many ZWO users will opt to control their AM5N from an ASiair, but for our review we used third-party software to ensure compatibility for those who don’t use a full ZWO setup.
We found that installing the ASCOM-compatible drivers was beautifully simple, which is always a pleasant surprise with new products.
We also installed ZWO’s SkyAtlas control app onto our phone, keen for the clear night ahead.
With Sequence Generator Pro (SGPro) open, we first connected our laptop to the AM5N via USB and selected ZWO as the mount type; the software detected the mount without issue.
Selecting the star Vega from our target list, we were pleased to see the AM5N respond without hesitation.
From the laptop, we parked the mount and disconnected the USB cable, so we could try out one of the mount’s other connection options.
ZWO AM5N Wi-Fi and Bluetooth
First connecting our laptop to the ZWO AM5N Wi-Fi network, we were still easily able to control the mount again via SGPro.
The ZWO AM5N’s new Bluetooth connectivity proved equally as straightforward; after selecting it in the SGPro driver, it prompted us to press the Bluetooth (BT) button on the AM5N to confirm the connection and we were again up and running.
Similarly, we used our phone to test both the Wi-Fi and Bluetooth control connection via the SkyAtlas app and again controlled the AM5N without any issues.
Polar aligning
With the skies now dark, we set about polar aligning, which was achieved by drift aligning in another third-party software, PHD2.
The azimuth and latitude adjuster proved easy to use, allowing us to make the fine adjustments required for a precise alignment.
We were pleased to note that that alignment didn’t shift when we tightened the altitude locks.
How the ZWO AM5N mount performs
With everything set, we slewed to the North America Nebula in Cygnus, calibrated our guiding
and set our CCD camera to capture 15-minute exposures.
Monitoring our guide graph closely, we were gratified to see a flat graph with very few corrections applied, even via PHD2’s default settings.
The flat graph was further confirmed by perfectly round stars in our final images.
With its simple design, vast array of connection options and lightweight but high-capacity abilities, the ZWO AM5N was a real pleasure to use.
It’s clear that ZWO has listened to feedback and produced a product that will convert many to the harmonic drive design.
Upgraded harmonic drive
The original ZWO AM5 had a load capacity of 12kg without the counterweight, which on the latest AM5N model has been upgraded to 15kg (or 20kg with the optional counterweight).
This increase has been achieved using new harmonic motors and an improved strain wave geared reducer.
The inclusion of these new motors and gearing system has also significantly improved the mount’s tracking performance, delivering +/- 10 arcsecond accuracy, reduced from +/- 20 arcseconds on the original.
This has all been achieved while maintaining a mount weight of just 5.5kg, ensuring the AM5N remains portable despite its capabilities.
One potential issue with harmonic drives arises during unexpected power loss.
Traditional equatorial mounts can hold position through a series of gears and clutches, allowing power to be lost without consequence.
Harmonic drives, on the other hand, offer no friction without power, which can cause telescopes to crash into the tripod.
To counteract this potential issue, the mount has an auto brake that triggers if power is lost, ensuring the safety of the equipment.
ZWO AM5N best features
Power pass through
Located on the mounting saddle is a 2.1mm power jack. This can be used to power any 12V accessory that uses a 2.1mm socket, including astronomy cameras or astrophotography controllers. The power for this socket comes from the main mount’s power, so only a single power supply is required.
Bluetooth
As an update to the AM5, the AM5N includes Bluetooth connectivity in addition to Wi-Fi and USB. The Bluetooth connection is compatible with ZWO’s SkyAtlas app and the ASCOM PC driver. A big advantage is that you can connect your phone to the mount via Bluetooth while a PC or ASIair is connected via Wi-Fi.
Carbon-fibre tripod
The ZWO AM5N can be supplied with the ZWO TC40 carbon-fibre tripod, adjustable from 470mm to 800mm and weighing just over 2kg. This is less than some standard photography tripods weigh, but the 40mm diameter legs were exceptionally sturdy once extended. We had no concerns about the tripod becoming unstable during setup and use.
Dual-fit saddle
The ZWO AM5N has an all-metal saddle that can comfortably hold both Vixen and Losmandy mounting plates. The saddle has two independent clamps that are easy to adjust thanks to the large and grippy metal thumbscrews, which ensure even the heaviest equipment attaches to the mount securely.
SkyAtlas app
The free SkyAtlas app, available on both Android and iPhones, allows full control of the AM5N. Its main screen is a beautiful planetarium setting that can be used standalone to plan your observing or imaging session, but once connected to the mount provides full Go-To capabilities.
Vital stats
- Price: £2,580
- Mount type: Harmonic drive dual mode (EQ/altaz)
- Load capacity: 15kg; 20kg with counterweight
- Slew speed: 9 speeds, up to 6° per second
- Power: 2.1mm, 12V DC
- Autoguider port: ST4
- Protocols: ASCOM compatible (LX200)
- Weight: 5.5kg mount; 2.3kg tripod
- Supplier: 365 Astronomy
- Tel 020 33 845187
- www.365astronomy.com
This review appeared in the October 2024 issue of BBC Sky at Night Magazine.