The Sky-Watcher Star Adventurer GTi is a compact and affordable GoTo mount. But does it find and track objects well enough for astrophotography?
Astrophotographers had been waiting for a mount like this, one that is compact and easy to pack for flights to dark sites yet with all the features demanded for deep-sky imaging: easy polar alignment, GoTo pointing, and dual-axis auto-guiding.
My questions were: would Sky-Watcher’s new Star Adventurer GTi align and find targets accurately; would it be solid enough to hold even small scopes solidly during long exposures; and would it track and guide well enough for consistently pinpoint stars? As I discovered over several nights of use, the answers were all yes — though with some caveats.
The GTi mount and Tripod
Several years ago, Sky-Watcher introduced the AZ-GTi, now $475, a compact alt-azimuth GoTo mount designed for visual observing. You can read Lee Pullen’s review of it here at AstroGearToday.
Astrophotographers looking for an airline-portable GoTo mount managed to hack the AZ-GTi into performing as an equatorial mount. Sky-Watcher’s Global website even offers a firmware update to facilitate this, but warns, “Performance for astrophotography is not guaranteed and [the] average customer might experience challenges in obtaining the result that they expected.”
Seeing astrophotographers kludge a mount that was never intended for imaging must have prompted Sky-Watcher to develop a compact mount that was. The result is the new Star Adventurer GTi, sharing the family name with two other Star Adventurer sky trackers. I reviewed the latest of those models, the WiFi-enabled Star Adventurer 2i here for AGT, and the older, smaller Star Adventurer Mini here.
However, the GTi member of the Star Adventurer family is quite different. While it is WiFi enabled, it operates from another app – the SynScan Pro app – not the SA Console app used to set up the other two Star Adventurers. In fact, the SA Console app doesn’t even recognize the GTi. As such, the GTi does not have any of the time-lapse motion-control functions the other Star Adventurers offer.
The bottom of the GTi’s head has a threaded 3/8”-16 hole for bolting it to any standard tripod top plate. For example, I used it with the Radian Carbon Fiber Tripod I reviewed here. But the GTi can be purchased in a kit with a Sky-Watcher aluminum tripod and pier extension. They weigh 8.2 pounds (3.7 kg). The Sky-Watcher tripod collapses to a minimum length of 29.5 inches (75 cm), a little long to fit into an average-sized suitcase for airline travel.
The GTi is rated as handling a load weighing up to 11 pounds (4.9 kg). I tested it most nights with a 61mm refractor weighing close to the limit (with camera, ASIAir controller, and guidescope) at 4.2 kg. It balanced fine using the GTi’s included 2.4 kg counterweight and for the most part tracked and guided well for images such as the one above.
A 76mm refractor rig weighing 4.9 kg, right at the specified limit, didn’t quite balance in RA but was close. However, sets of auto-guided images (as above) showed almost perfect guiding in all but the occasional frame, so this did prove a workable combination for imaging.
Using a high-power eyepiece in the 76mm refractor, vibrations damped down in about three seconds, so just acceptable. After I slewed to Jupiter the GTi kept it dead center at 120x over a two-hour test, impressive indeed for a small mount.
GTi Polar Alignment
Unlike a lot of mounts introduced in recent months, the GTi has a traditional polar alignment scope in its polar axis, so it doesn’t require having a computer at hand to perform electronic polar alignment with a camera. I like that, as it makes for less gear to carry and less to go wrong in the field.
I found the polar scope accurate and the mount’s altitude and azimuth adjustments easy to use and fairly solid and secure. Unlike the other Star Adventurer trackers, which use add-on LED illuminators that are easily lost or left switched on, the GTi has a built-in LED for lighting the polar scope’s field, but not the reticle per se. The LED’s brightness is controllable via the app, and the reticle is etched with the locations of stars around Sigma Octantis for polar alignment in the Southern Hemisphere, great for trips down under.
GTi GoTo Operation
My iPhone or iPad always saw the GTi’s ad hoc WiFi network and connected to it quickly each time. From there you select one of the methods under Alignment. I usually used Three Star where, from the standard starting position aimed north shown above, the GTi slews in turn to three stars you select from the list the app presents to calibrate its GoTo pointing.
Navigating the app’s menus takes a little getting used to. For example, planets and comets are located under the Star menu option. While there is a PDF manual available for the app, it’s technical and poorly illustrated – or rather, it’s not illustrated at all! The abbreviated in-app Help menu, found under Utility, is of slightly more use.
Of note, while the instructions claim you cannot also control the mount from a third-party app like SkySafari using the same Apple iOS device, that’s untrue. Install the SynScanLink app, then when opening SkySafari’s Telescope control menu, choose SynScanLink as the connection protocol. You can now run the mount from either the SynScan Pro app or SkySafari, or both, with the latter providing a superb star atlas view of where you are pointed.
While most people will run the GTi off a phone or tablet, it is possible to plug in a SynScan hand controller (a $155 option) and perform GoTo alignment and slews the traditional wired way without WiFi. I used the Version 5 hand controller from my Sky-Watcher EQM-35 Pro mount and it worked well.
Either way, GoTo pointing was accurate enough to place objects within the field of a low-power eyepiece or camera, often dead center but in some parts of the sky as much as a degree off. Slewing isn’t fast, taking 45 seconds to go from Arcturus in the west to M31 in the east, but it gets the job done and settles on a target quickly. Both the app and hand controller allow the mount to be Hibernated so it can be powered up the next night and not need realigning.
The GTi has hard stops which prevent it from tracking or being slewed more than about 15° on either side of the meridian. Yes, I understand this is a safety measure to prevent a telescope that is aimed up high from hitting the tripod or pier. But … when using the GTi just as a tracker, I found it simply stopped dead about an hour after passing the meridian. That was a surprise!
I encountered some other GoTo glitches. Even after successfully aligning and going to targets, one night I found the GTi oddly tracking way too fast, turning at what looked like 2x sidereal rate. Objects slowly drifted out of the eyepiece. On another night when using the SynScan hand controller, the mount would reboot the controller upon starting a GoTo slew.
I found these issues could be attributed to running off the internal AA batteries when they were low in voltage. Switching to an external 12-volt lithium battery cured such bad behaviors. Usually. Even using a fully charged external battery I found the GTi sometimes pointed way off during setup or when waking from Hibernate. It took force-quitting, then re-launching the SynScan Pro app to clear what seemed to be bad position data retained in its memory.
I found a set of fresh alkaline AAs lasted only two or three mild autumn nights, and that was with mostly tracking and a minimum of GoTo slewing. (The specs claim 10 hours of tracking on internal batteries, which proved about right.) Annoyingly, plugging in an external battery with the mount powered up causes the GTi to shut off momentarily, requiring a new GoTo alignment. The GTi can run off external power even if no internal batteries are installed.
The power issue is made worse by the fact that neither the SynScan Pro app or the LED on the control panel provide any indication of battery level or low voltage. I found nothing in the instruction manual that explains why the panel’s LED usually double blinks but at times is solid red (the latter seems to be when the WiFi shuts off, though it is not clear under what circumstances that happens).
I understand the LED behavior might be a firmware bug. I was unable to update the firmware as Sky-Watcher’s utility for doing so runs only on Windows. I use a Mac.
GTi Tracking and Guiding Accuracy
The GTi can be used as a normal polar-aligned tracker, just free-wheeling without any autoguiding or GoTo alignment. (Just turn on Tracking>Sidereal under Utility.) This is the simpler way to use it for wide-angle images. When shooting with a 135mm telephoto lens, I found 25 to 50 percent of my two-minute test exposures showed some level of trailing from mis-tracking, on par with the other Star Adventurer trackers.
However, the GTi’s attraction is its ability to be auto-guided in both axes to correct any such mis-tracking, allowing long exposures with longer focal length optics. On some nights I used the GTi with the stand-alone Lacerta MGEN3 autoguider I reviewed here for AGT. It auto-guided the GTi with no major issues using the GTi’s standard ST-4 autoguider port, including applying positional “dithering” offsets between each exposure to help average out noise when stacking frames.
Compatibility with the ASIAir
On other nights I ran the GTi using ZWO’s ASIAir controller, the older Pro model which I reviewed here, not the newer Plus model. The Air Pro connected to the GTi’s USB port without complaint by selecting the Sky-Watcher AZ-GTi protocol in the ASIAir app, not the standard SynScan option.
The ASIAir controlled the GTi very well, first for performing an electronic polar alignment, then slewing to targets and performing plate-solving moves based on the ASIAir app’s built-in database. The Air also auto-guided the GTi fine through the USB port, rather than via the GTi’s ST-4 autoguider port, again applying dithering moves with no issues. (I did not test the GTi with N.I.N.A., Astro Photography Tool, PHD2, or other Windows desktop control or autoguiding programs.)
With both the ASIAir and the Lacerta MGEN3, some sets of images were perfectly guided, with RMS errors typically under two arc seconds using 30mm mini-guidescopes. However, I did occasionally find frames where the guiding went wonky in either RA, Dec, or both. While that can happen with any mount, I found the GTi more prone to badly trailed frames than larger mounts; its gears are tiny after all.
I view the Star Adventurer GTi as serving two types of customers: beginners wanting to try their hand at deep-sky imaging with a minimum investment, and well-equipped astrophotographers looking for a compact but capable mini-mount for travel to remote skies. The GTi can work well for both buyers. But from my experience I would add some caveats:
- While the GTi can be used just as an unguided tracker, its GoTo features, such as hard stops, can actually get in the way of simple tracker use.
- Always shoot more frames than what you might need, as the small gears in the GTi are bound to mis-track at times, yielding trailed stars and frames you have to discard.
- Be sure to have spare, fresh batteries at hand or, better yet, an external 12-volt source for more reliable power than the internal AAs.
- If the mount continues to act oddly, learn to force-quit the app and start again.
- For airline travel coupling it to a sturdy carbon fiber tripod makes for a lighter, more compact, albeit more costly package than using Sky-Watcher’s tripod.
- Don’t load the mount with more than what it’s designed to handle. An ideal companion is a fast 50mm to 60mm apo refractor. While I found it can handle a lightweight 76mm refractor, I feel that’s the practical limit, as per the mount’s specifications.
- For heavier telescopes look at Sky-Watcher’s larger German equatorial mounts, like the EQM-35 Pro, the next step up in their mount lineup for size and cost. I reviewed that mount here for AGT.
However, the Star Adventurer GTi is a great choice for anyone looking for a low-cost and ultra-portable mount for astrophotography paired with equally portable and lightweight optics.
Compact and portable
Accurate enough GoTo pointing
Good autoguiding performance
Polar alignment scope included
Misbehavior with low batteries
No battery level indication
App can be confusing to use, and occasionally needs force quitting
Hard stops either side of the meridian
MSRP: $640 (Head Only); $740 (With Tripod and Pier Extension)