Sky and Telescope - May 2017 - 70

Star Trackers

Vixen Polarie Star Tracker
vixenoptics.com * Starting at $399

The sleek Polarie Star Tracker is a compact, rectangular drive that attaches directly to
your tripod with a ¼-20 threaded socket (S&T: March 2012, p. 58). Weighing just 1½
lbs., it can handle cameras of up to 3½ lbs. The base model is aligned using a peep
sight to point toward Polaris, which is accurate enough for exposures up to a couple
of minutes with a wide-angle lens. A built-in inclinometer (tiltmeter) helps you accurately set the altitude adjustment. It can be operated in both Hemispheres and offers
sidereal, 0.5× sidereal, lunar, and solar drive speeds. The unit is powered using 2 AA
batteries that last about 4 hours; it and can also be powered via a mini-USB port.
Additional options for the Polarie include an unilluminated polar-alignment scope,
ball head, time-lapse adapter, and a Polar Fine Adjustment Unit that's very useful
for exact altitude and azimuth adjustments. Vixen also offers a Polar Meter with
a built-in bubble level and altitude scale for daytime alignment (as when shooting
solar eclipses).

Fornax Mounts LighTrack II
fornaxmounts.com * Starting at about $458

This mount appears similar to the AstroTrac seen below, but it's driven using a
ﬂat-wheel friction drive with a claimed peak-to-peak drive error of 2 arcseconds
over an 8-minute period. Like the AstroTrac, the drive needs to be reset about
every 2 hours. The LighTrack II weighs 2.9 lbs. and can carry 13.2 lbs. It will operate in both the Northern and Southern Hemispheres at sidereal, 0.5× sidereal,
lunar, and solar rates. It also has an autoguider input for right ascension corrections. The LighTrack II is powered via a 12V DC cigarette-lighter cable. Additional
accessories include a Sky-Watcher HM5 polar scope and adapter thread and
the FMW-200 adjustable wedge.

AstroTrac TT320X-AG
astrotrac.com * Starting at $619

The AstroTrac is a futuristic-looking drive that doesn't use a traditional
gear and worm drive. Instead, it utilizes a "worm rod" that is actually a
section of screw with ﬁne threads in a tangent arm that will track for 2
hours before the screw needs to be reset. The unit weighs 2.2 lbs. and
can carry a hefty payload of up to 33 lbs. It operates in both the Northern
and Southern Hemispheres with sidereal, lunar, and solar rates electronically controlled for accuracy.
AstroTrac claims an unguided peak-to-peak tracking error of about
5 arcseconds over a 5-minute period. The TT320X-AG also has an ST4-compatible autoguider port for autoguiding in right ascension.
While the drive comes with a DC power cord, an 8-AA battery holder
is an additional option, as is an illuminated polar-alignment scope, a ball
head, and various accessories to make the drive into a complete equatorial mount capable of bearing small telescopes with ease.
* Follow Contributing Editor JERRY LODRIGUSS as he discusses
astrophotography techniques in a monthly blog at skyandtelescope.com.

M A Y 2 0 1 7 * SK Y & TELESCOPE

http://www.vixenoptics.com http://www.fornaxmounts.com http://www.astrotrac.com http://www.skyandtelescope.com

Sky and Telescope - May 2017

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