William Optics Cat 91 + ZWO AM5N Traveler Imaging Kit

More aperture and reach in a kit that still sets up without a counterweight

The William Optics Cat 91 + ZWO AM5N Traveler Imaging Kit is a complete deep-sky astrophotography setup: a 91mm f/4.9 Petzval astrograph with a 55mm image circle and no flattener needed, the ZWO ASI2600MC Air color smart camera with built-in ASIAIR and guider, the AM5N strain wave GoTo mount with the TC40 carbon fiber tripod and PE200 pier extension, and ZWO's 12V 5A AC power adapter. Together the camera and telescope frame 3.0° × 2.0° of sky, enough for the whole Andromeda Galaxy with a closer view of smaller targets. Everything weighs about 16.5kg (36.3lb).

Key specs: Cat 91: 91mm aperture, 448mm focal length, f/4.9, 5-element Petzval, 55mm image circle · ASI2600MC Air: 26MP APS-C IMX571, cooled, built-in guide sensor and ASIAIR, 256GB storage · 3.00° × 2.01° field at 1.73″/pixel · AM5N: 15kg (33lb) payload without counterweight, ±10″ periodic error · TC40 tripod and 200mm pier extension included

The Cat 91 AM5N kit is on display in our Denver store, so you can see it in person before you buy.

What you can image

• Nebulae: the North America Nebula, the California Nebula, the Rosette Nebula, the Seagull Nebula, the Eastern or Western Veil, and the Elephant's Trunk.
• Galaxies: the Andromeda Galaxy fills the frame, and the Triangulum Galaxy, the M81 and M82 pair and the Leo Triplet show more detail than at shorter focal lengths.
• Winter favorites: the Orion Nebula with the Running Man, the Horsehead and Flame Nebulae, and the Pleiades with their dust.

With the ASI2600MC Air, the Cat 91 gives a 3.00° × 2.01° field at 1.73 arcseconds per pixel.

How it works

Mount and tripod: open the TC40, set the PE200 pier extension on it, and set the AM5N on top. There's no counterweight to add and nothing to balance. The pier extension raises the mount 200mm so the camera clears the tripod legs when the telescope points high.

Telescope and camera: the Cat 91's Vixen-style plate fits the AM5N's saddle. The ASI2600MC Air threads onto the telescope's M54 camera adapter. William Optics lists a maximum sensor spacing of 65.8mm from the M54 thread (60.8mm from M48), and the camera with its included spacers sits at 55mm, well inside that, with the 36mm of focuser travel taking up the difference. The WIFD focuser moves the optics inside the tube, so the camera never hangs off a drawtube, and the tilt adjuster and rotator let you square and frame the sensor.

Power and control: plug the 12V supply into the camera and run the included DC cable from the camera to the mount. The Air connects to the AM5N over USB or Bluetooth, and you run polar alignment, GoTo, focusing, guiding and imaging from the ASIAIR app on your phone or tablet over dual-band Wi-Fi. Images save to the camera's 256GB of built-in storage.

Using it in Colorado: the AM5N works down to -20°C (-4°F), and ZWO's high-load mode in the app helps the mount in cold weather. Dark sites a couple of hours from Denver rarely have an outlet, so plan on a 12V power tank there.

What to add for the best results

• Field power: a 12V power tank such as the Celestron PowerTank Lithium Pro runs the camera and mount away from an outlet.
• Autofocus: a ZWO EAFN or EAF Pro plugs into the Air's USB hub, with the K-Astec EAF bracket with clutch made for WIFD focusers. It keeps stars sharp as the temperature drops.
• Light-pollution filter: a 2" ZWO Duo-Band or Optolong L-eXtreme filter in a ZWO M54 2" filter drawer for nebulae from city and suburban skies. The drawer takes the place of part of the spacer stack, and we can help you set it up.
• TC40 tripod case: a padded bag for carrying the tripod.

Which Traveler kit is right for you?

Read more about each piece on the William Optics Cat 91, ZWO ASI2600MC Air, ZWO AM5N with TC40 tripod and ZWO PE200 pages, or see all astro imaging kits.

What's in the box

• William Optics Cat 91 WIFD in black (some photos show the red version) with tilt adjuster and rotator, Bahtinov mask cap, M48 and M54 camera adapters, Vixen-style dovetail plate, mounting ring and handle bar, riser blocks, soft carry case and Allen key set
• ZWO ASI2600MC Air with antenna, 1.5m DC extension cable, two 1m power cords, two 0.5m USB 2.0 cables, 16.5mm M54 adapter, 21mm M54 extender, M54 to M48 ring, cable strap, hex wrench and quick guide
• ZWO AM5N mount head with hand controller and cables
• ZWO TC40 carbon fiber tripod
• ZWO PE200 pier extension
• ZWO 12V 5A AC to DC adapter (US plug, 60W)

Filters, an electronic focuser, a counterweight and field power are sold separately.

Cat 91 AM5N Traveler Kit FAQ

Is this a good first astrophotography setup?

Yes, if you're ready to learn a real imaging setup. There's no flattener spacing to calculate, no mount to balance and no separate guide scope, and the ASIAIR app walks you through polar alignment, focusing and guiding. If you want push-button results with no setup, a smart telescope is the better choice.

Do I need a guide scope or a computer?

No. The ASI2600MC Air has a guide sensor beside the main sensor and the ASIAIR controller built in, so you guide through the main telescope and control everything from your phone or tablet.

Can I see one before I buy?

Yes. The Cat 91 AM5N kit is on display in our Denver store, and we're happy to set it up and show you how it works.

Cat 91 or UltraCat 76?

The Cat 91 has more aperture and a 448mm focal length, a 3.0° × 2.0° field that suits galaxies and smaller nebulae. The UltraCat 76 kit frames 3.7° × 2.5° for the biggest nebulae, is about 1.3kg lighter and costs less.

Can I use a full-frame or medium format camera later?

Yes. The 55mm image circle covers full frame, and William Optics says medium format cameras work with an additional adapter.

Can I use it for visual observing?

No. William Optics designed the Cat 91 for cameras only and doesn't support visual observing with it.

What power does it need?

The included ZWO 12V 5A adapter runs the camera, and the camera passes 12V to the mount. Away from an outlet, use a 12V power tank.

Specifications