Using the MGEN3 requires some cable management! Shown here with the Sky-Watcher EQM-35 mount and SharpStar 76mm EDPH scope. Credit: Alan Dyer

The Lacerta MGEN3 is a truly stand-alone autoguider with advanced functions such as camera control, dithering and polar alignment assistance.

Plus: Truly stand-alone; easy to power; offers camera control and dithering
Minus: Costly; limited availability

Summary: The MGEN3 requires no computer or mobile device; all operations are controlled via on-screen menus, making this a good choice for those who wish to avoid computers. Autoguiding proved accurate and reliable.

Who Is It For? DSLR camera users seeking accurate computer-free autoguiding.

Since the early 1990s I have tested and used a number of “stand-alone” autoguiders, starting with Santa Barbara Instruments’ pioneering ST-4, to their recently discontinued SG-4. As a user of just DSLR, and now mirrorless, cameras, I prefer not to fuss with computers at the telescope, either for camera control or for autoguiding. A stand-alone autoguider requires no computer and, ideally, offers one-button operation — just “push here” and it starts guiding.

However, a few stand-alone autoguiders offered over the years that I’ve tested proved insensitive, requiring a lot of finicky work to place a suitably bright star onto the small sensor of the autoguider’s camera.

By contrast, the Santa Barbara Instruments SG-4 was marvelous for always being able to guide flawlessly on whatever starfield it was aimed at, and to start guiding with one click. It’s been my gold standard guider.

I’ve always been on the lookout for new autoguiders with similar ease of use. The new Lacerta MGEN3 comes close, with the benefit of doing much more than the old SG-4 ever could.

Autoguiding with the MGEN3

Lacerta is a small company based in Hungary offering a number of unique astronomy products. Introduced in 2020, the MGEN3 is, as the name implies, the third generation of its stand-alone autoguider. The core of the package is the small control box with a color LCD screen for displaying setup menus, guiding camera images, and the autoguiding graphs.

The MGEN3 Components. Credit: Alan Dyer

The included autoguider camera uses a 1288 x 968 pixel (or 4.8mm x 3.6mm) monochrome sensor. The package includes a standard ST-4 cable for connecting the control box to the ST-4 autoguider port of a telescope mount. Also included are two identical USB cables: one for connecting the camera to the control box, and the other for connecting the control box to any standard USB power source.

The MGEN contains no battery, but can be powered from any small 5-volt power pack used to charge phones. Power draw is stated as 240 milliamps. I often used Celestron’s PowerTank Glow 5000 flashlight, which powered the MGEN for several nights. By contrast, the old SG-4 drew close to 3 amps at 12 volts, making it a challenge to power in the field.

The user needs to supply a suitable guidescope and means of securely attaching it to your imaging telescope. I used a William Optics Uniguide, a compact 32mm-aperture guidescope with a Vixen-standard base for $100. It works very well with the MGEN camera.

The little camera comes with two nosepiece adapters: one with a 1.25-inch (31.7mm) barrel, the other with an M42 or T2 female thread. The 1.25-inch nosepiece worked with the Uniguide scope. Another guidescope I use, a Borg 50mm, required the T2 adapter. Either way, attaching the camera to your guidescope should be easy.

The little guide camera comes with two nosepieces with standard threads for mating it to a variety of guidescopes. Credit: Alan Dyer

As with all autoguiders, the key first step is getting the camera focused with the guidescope. That can be done during the day by aiming at a distant target and setting the camera to take very short looping exposures that stream to the control box’s screen.

Apart from entering the focal length of the guidescope, the MGEN tries to be as “push here” as possible. There is a “One-Push” option that takes an exposure to fill the field with stars, then starts the calibration moves in each axis. That process takes less than a minute, then the guiding begins.

The MGEN guides on not one but on a field of stars, up to 100, to avoid the errors that can be introduced from poor seeing by guiding on just one star. The claim is for greater guiding accuracy and smaller stars in the final image. While I did not test the MGEN against the single-star guiding of another guider on the same night, I found that the MGEN3 did guide consistently well, producing tight star images with no odd trailing, and with no need to fuss with arcane guiding parameters.

It is possible to take a dark frame that it stores on its internal microSD card and automatically subtracts, to avoid the guider from being confused by hot pixels. Once guiding is underway, you can see either the count of exposures taken and remaining, or switch to a display of the guiding corrections. I would have liked a screen option that shows both. I was pleased to see that operation and screen visibility wasn’t hampered by sub-freezing temperatures.

Advanced Functions

One of the main attractions of the MGEN3 is that it can control the shutter of a DSLR or mirrorless camera. (I used it most nights with my Canon EOS Ra.) It does this by connecting to the shutter release port of the camera, to trigger the shutter with a switch closure as would any remote release or intervalometer.

The surprise was that the MGEN3’s shutter port uses a 3.5mm mini-phono jack, not the 2.5mm standard used by all intervalometers for their cables. So connecting to a camera requires a specialized cable, to go from the MGEN’s 3.5mm jack to your camera’s shutter port, which might be a 2.5mm jack or some other proprietary socket.

When I purchased the MGEN3 from 365Astronomy in the U.K. the need for this specialized cable was not clear. When I later ordered a pair of cables for my two types of Canon cameras, 365Astronomy sent the wrong cables, ones with just 2.5mm plugs. So even they were confused! We sorted that out. But be aware that to control a camera you will need a specialized cable offered by Lacerta. Or, as I did as well, you can find a male 3.5mm-to-female 2.5mm audio adapter at a local RadioShack outlet, to allow using an existing intervalometer cord.

From left to right, screens allow setting: the guidescope focal length; setting exposure time and camera gain and viewing the live image for focusing; dithering parameters; button and screen colors and brightness; and guiding graph options. Credit: Alan Dyer

The MGEN3 has a menu page where up to four preset exposure sequences can be saved, each defining the number of exposures and length of exposure. It is not possible to program in a sequence with a mixed set of exposure times, but I’ve never found that essential.

With the MGEN3 running the camera shutter, it can be set to “dither” exposures. With this option engaged, the guider will automatically shift the mount by a user-defined number of few pixels after each exposure, resume guiding, then start the next exposure. The resulting images will be randomly out of register. Re-aligning the images in processing then de-registers any thermal noise hot pixels, canceling them out when stacking and averaging the aligned images.

The dithering function worked very well, and took just seconds to perform between exposures. Using it means taking and subtracting dark frames might not be necessary, speeding up image acquisition and simplifying the processing workflow. It’s a major benefit of the MGEN3.

Another advanced function is the inclusion of a digital polar alignment aid. Unlike the routines used by the ASIair, Polemaster, iPolar and SharpCap, which all “plate solve” by aiming at the celestial pole, the MGEN3 uses a classic two-star drift method. You aim at a starfield on the celestial equator to the south, then at a starfield near the celestial equator rising in the east.

After only a couple of minutes aimed in each direction the MGEN screen displays the polar alignment error measured by detecting the pixel-level drift in the stars’ positions. The display instructs you on which way to adjust the polar axis (up-down or left-right) to improve the accuracy, and you can watch in real time as the numbers improve. I found this worked well and is another superb feature not found on other true stand-alone autoguiders.

For all the details of the MGEN’s specs and operation, download the instruction manual here at 365Astronomy.

MGEN Caveats

I tested the unit with firmware v1.03 (v1.05 is now current as of late January 2021). Updating the firmware to add new functions is possible, but one method requires a Windows computer to run the updater program.

The other option is copying the downloaded firmware .bin file plus a “key file” (a text file with a code unique to your registered account) to the MGEN’s microSD card and updating from the card. Doing that on a Mac proved problematic, as I found I had to use the Mac’s “Get Info” panel to rename the key file to remove the .txt suffix the MacOS added to it, so the MGEN would recognize the file and proceed with the update. It took several email exchanges with Lacerta to solve that issue as, apparently, I was the first Mac user to ever attempt a firmware update.

I did find that on occasion the One-Push operation failed to start or complete the Calibration process automatically. Or it gave a cryptic error message. I had to start calibration manually or just turn off the MGEN and try again.

While the setup involves managing several cables, having the control box separate from the guiding camera allows settings to be adjusted without bumping the scope or mount.

As of this writing, the Lacerta MGEN3 is not available from any U.S. dealer. Ordering from the U.K., as I did, worked fine, but inevitably incurs import fees and taxes, adding to the cost. As of this writing the only North American dealer for the MGEN3 is in Canada, at FerventAstronomy.com who sell it for $1,000 Canadian (about $800 U.S.). European buyers have several dealers to select from, with the cost listed as €750 with VAT.

Yes, the MGEN3 is a premium autoguiding solution (don’t forget to factor in the cost of the guidescope). On the other hand, the stand-alone SG-4 was selling for well over $1,000 U.S. before it was discontinued, and it didn’t offer multi-star guiding, dithering or polar alignment assistance.

The Pacman Nebula. I did not use Long Exposure Noise Reduction or any dark frames, to test the effectiveness of the dithering in averaging out the thermal noise. It seemed to work fine! Credit: Alan Dyer

The MGEN3 does work very well, and is an excellent choice for anyone who shoots with DSLRs and mirrorless cameras and wants to keep their deep sky imaging rig as simple as possible, yet still have the benefit of advanced functions such as digital polar alignment and dithering.

MSRP:  $730

Website:  https://mgen-autoguider.com/en/

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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