ZWO AM7 Harmonic Mount with William Optics Pier Mount 90

A 44lb-capacity harmonic mount on a rock-solid pier, with no counterweight needed

The ZWO AM7 with Pier Mount 90 pairs ZWO's larger strain-wave (harmonic) equatorial mount with William Optics' aluminum field pier. The AM7 switches between equatorial and alt-az modes, runs from the ASIAIR or ZWO's free app over Wi-Fi or Bluetooth, and is rated to work down to −20°C. The pier gives it a wide, low-vibration stance with leveling feet, and the whole set weighs about 30lb, light enough to carry out to the backyard in two trips.

Key specs: AM7 payload 20kg (44lb) without counterweight, 30kg (66lb) with · periodic error ±10″ with individual test report · 300:1 harmonic drive · 6.75kg (15lb) head · latitude 0–90° · USB-C and DC ports on the saddle · Pier Mount 90: 90kg (198lb) capacity, 100mm (4") column, 7kg (15lb)

What it can carry

• Large refractors: 130–150mm apochromats like the Esprit 150 for deep-sky imaging.
• Big SCTs and RASAs: 9.25" and 11" Schmidt-Cassegrains and EdgeHDs for galaxies and planets.
• Dual rigs: two smaller imaging scopes side by side on a dovetail bar.
• Visual observing: in alt-az mode it becomes a GoTo mount for a large scope, with no polar alignment.

For payloads above 44lb, add a counterweight (ZWO suggests up to 10kg on a 20–30cm shaft).

How it works

Set the pier's three legs, level it with the adjustable feet, and attach the AM7 with the central 3/8" screw. Set your latitude in two stages (0–60° or 30–90°), mount your telescope on the saddle, and connect. The mount connects over Wi-Fi from its hand controller, or over Bluetooth, and joins your ASIAIR's network in station mode. Cables can run through the mount to the USB-C and 12V ports on the saddle, so nothing snags as it slews.

Harmonic drives don't need counterweights, so there's less to carry and no balancing on most setups. A magnetic hex wrench stores on the mount, and status lights switch to red to protect your night vision.

Using it in Colorado

• Wind: the pier's wide stance and stiff 4" column hold up better than a tripod in Front Range gusts.
• Cold: the AM7 is rated to −20°C (−4°F), so winter nights at altitude are fine. Bring 12V power that handles the cold well.
• Uneven ground: the pier's adjustable feet level it on a gravel pad, a deck or a mountain campsite.

What to add for the best results

• ASIAIR Plus: controls the mount, camera, guiding and focuser from your phone.
• ZWO ASI2600MC Air: a camera with an ASIAIR and guider built in, for the simplest imaging setup on this mount.
• ZWO 12V 5A power adapter for backyard use.
• Celestron 34" tripod soft case: fits the Pier Mount 90 for transport.

AM7 with Pier Mount 90 vs. AM7 alone vs. AM5N

What's in the box

You get the AM7 mount with its accessories shown above, plus the William Optics Pier Mount 90 with Mile High Astronomy's tool-free knobs and nylon washers. Counterweight, power supply and carry case are sold separately.

ZWO AM7 with Pier Mount 90 FAQ

Do I need a counterweight?

Not for payloads up to 44lb. Above that, a counterweight raises the limit to 66lb.

Can I use it for visual observing?

Yes. Switch the AM7 to alt-az mode and use it as a GoTo mount from the app with no polar alignment.

AM7 or AM5N?

Choose the AM7 for setups over about 28lb, like 130mm+ refractors and 9.25"–11" SCTs. Choose the AM5N if you travel often and your scope is lighter.

Does it work with the ASIAIR?

Yes. It connects to the ASIAIR by USB, or over Wi-Fi in station mode, for GoTo, plate solving and guiding.

Why a pier instead of a tripod?

A pier puts the weight on a single stiff column with a wide footprint, so it damps vibration faster and resists wind better. The Pier Mount 90 is still portable at about 15lb.

How tall is the pier?

The Pier Mount 90 stands 89.3cm (35") set up and 79.3cm (31") closed, with 15mm of leveling adjustment in each foot.

Specifications