Autoguiding with the ZWO ASIair Pro

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AIRAir and ASI guidecamera being tested on images of M31 Credit: Alan Dyer

ZWO’s ASIair Pro offers an attractive and expandable option for those looking for an easy-to-use autoguider rig.

Plus: Accurate guiding in a fairly easy-to-use interface

Minus: Requires tablet or phone to remain connected; limited camera control

Summary: The ZWO ASIair serves as a hub for controlling both an autoguider and main imaging camera through a wireless app. The autoguiding function works very well. Camera control is more limited.

Who Is It For? Astrophotographers seeking laptop-free autoguiding.

I prefer to keep my array of gear at the telescope as simple as possible when doing deep-sky photography with DSLR and mirrorless cameras. As such, I like autoguiders that don’t require a laptop in the field, to minimize cables, power requirements and the need to find a place for the laptop. Computer-free autoguiders are called “stand-alone.”

ZWO’s ASIair offers a package that isn’t quite stand-alone, as it still requires a mobile device — a phone or tablet connected via WiFi. However, using an ASIair does ease power and connection issues. The benefit is that the ASIair and its mobile app can do much more than just autoguiding. However, it is that function I test here. 

The ASIair guiding the Sky-Watcher EQM-35 mount and William Optics RedCat 51mm. Credit: Alan Dyer

Autoguiding with the ASIair

The ASIair Pro is a smartly packaged computer (a version of a Raspberry PI) that sets up a local WiFi network. You connect to it via your phone or tablet (I used my iPad for the testing), using the free ASIair app (for iOS or Android). 

The ASIair serves as a smart hub for powering and controlling several USB devices such as a ZWO imaging camera, filter wheel, and focuser, plus a select number of older DSLR cameras, and an autoguider camera. 

Connecting just an autoguider camera to the ASIair is the focus of this review, using ZWO’s ASI120MM guide camera attached to ZWO’s little 30F4 guidescope, a bundle offered by most dealers. You could use another ZWO camera for autoguiding, attached to any optics you like for the guidescope. But the combination of the 30F4 scope and ASI120MM camera makes for a solid, compact and relatively affordable autoguiding package. 

And despite the guidescope’s 30mm aperture and the ASI120MM’s small 4.3mm x 3.5mm monochrome sensor (with 1280 x 960 pixels), over many nights of use I never found the camera was unable to start guiding. There was always a bright enough star in the field no matter where it was aimed. Excellent! 

The app requires initially assigning the 120MM camera to the autoguider “slot” and to input the correct focal length (in this case 120mm) for the guidescope. That done, I found the app always connected to the camera without any issues. 

While using an app on a mobile device isn’t quite as stand-alone as I would like, it’s still much easier to power and operate a touch-screen tablet or phone in the field than it is fussing with a mouse, trackpad and keyboard of a power-hungry laptop. 

As most autoguider cameras do, the ASI120MM has a standard ST-4 port that needs to go to the autoguider port on your mount. A cable is included. The guide camera also needs to be connected to the ASIair Pro via an included short USB-C to USB-A cable, and the ASIair Pro has to be powered from an external 12-volt source you supply. So there’s a bit of cable management needed, but the only cable running off the scope is the power cord. 

I found navigating through the app’s various screens a bit confusing at first. Hitting the guiding graph (not an obvious navigation route) takes you to the dedicated autoguider screen where you can set exposure times, and thus how often guiding corrections are applied. 

The app displays a graph of guiding corrections similar to the popular PHD and PHD2 desktop programs. Guiding “aggressiveness” can be adjusted as it guides. Credit: Alan Dyer

Anyone who has used the free PHD2 Guiding program on a laptop computer [see https://openphdguiding.org] will find the interface familiar, as the ASIair’s guiding module is a variation of PHD2.

If you are using the autoguider on a tracker with a drive motor on only one axis, it is possible to turn off corrections in the Declination axis. I used the ASIair with both an iOptron SkyGuider Pro and Sky-Watcher Star Adventurer 2i and it worked fine on both trackers. 

Two-axis guiding on my German equatorial mounts, including the entry-level Sky-Watcher EQM-35, also worked well.  I encountered no issues with oscillations, runaway stars, or imprecise guiding — unless clouds moved in and the guide star disappeared. The app then proclaims “Star Lost,” in which case the autoguiding corrections can go wild, instead of just stopping.

So, the ZWO package isn’t quite PHD — push here dummy — for ease of operation. But once you get used to navigating and setting up the app, it does guide accurately and reliably. 

ASIair Caveats 

While the ASIair Pro and ASI120MM combination does free you from having a computer at the scope, you do need a phone or tablet to run the app. If your device loses power in the cold, then autoguiding fails. 

While you can bring your device inside to keep it warm, I found the ASIair’s 2.4 MHz WiFi reach was short, and the connection easily lost, again causing the guiding to fail. So having your tablet inside while you monitor the guiding from the comfort of your armchair might not be feasible. 

Also, using the app on a phone will likely require turning off cellular data, or else the app will see but not connect to the ASIair Pro. That’s a known bug.

While I found the autoguiding function worked great, I was hoping to make use of the ASIair to also control my main imaging camera, now a Canon EOS Ra mirrorless. However, as of this writing that camera, and many other DSLR and mirrorless cameras made in the last three years, are not supported. See ZWO’s list of supported cameras here.

A test image of M31. SharpStar 76mm EDPH apo refractor, Sky-Watcher EQM-35 mount, and guided with the ASIAir Pro and guidescope using iPad app. Credit: Alan Dyer

Being able to control the imaging camera’s shutter allows the use of “dithering,” where the ASIair will shift the image slightly by a few pixels between exposures to help minimize noise when stacking. 

The ASIair has a 2.5mm mini-phono jack labeled “DSLR,” which I had assumed was to trigger a camera shutter, like an intervalometer. But not so. It is only for long exposures with a select number of problematic Nikon DSLRs. 

Instead, the ASIair controls a DSLR camera through one of the Air’s four USB ports, making camera compatibility much more difficult and limited, as every camera model requires a different protocol. It would be so much better if ZWO simply used its existing 2.5mm jack to send a switch closure, so it could operate any camera shutter via a standard intervalometer cable into the camera’s remote jack.

So with my incompatible camera, I have yet to make full use of the ASIair Pro for both autoguiding and synchronized camera control, and therefore dithering. 

But when used just as an autoguider package, the ASIair Pro and its WiFi app do work very well. Unlike most other autoguiders, they offer the possibility to expand into camera control, digital polar alignment, and even GoTo mount control and “plate-solving,” advanced functions of the ASIair beyond the scope of this review.

MSRP: $299 for ASIair Pro, $547 for ASIair Pro with ASI120MM Mini camera and 30F4 guidescope

Website:  https://astronomy-imaging-camera.com/

About Alan Dyer

Alan Dyer is an astrophotographer and astronomy author based in Alberta, Canada. His website at www.amazingsky.com has galleries of his images, plus links to his product review blog posts, video tutorials, and ebooks on astrophotography.

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