Star Adventurer GTi

I wanted that kind of mount since the first time I have used a regular Star Adventurer. That size, weight, and load capability with added GoTo option – just a Star Adventurer GTi. One may ask a question: why do you need a GoTo mount in travel or holiday setup, where you have plenty of time for framing and taking care of your hobby? Well, I have two main reasons.

First: there is a possibility to dither in both axes. Especially when we use a DSLR camera or other camera without active cooling, that kind of dithering fights “walking noise” which is a banding noise that comes from the stacking of the frames, which due to the drift or only one axis guiding are more and more misaligned comparing to the first frame.
Second: you may plan your session in advance, program it, and then go to sleep. My holidays are usually pretty active during the day, not just lying on the beach, so I want to be well-rested in the morning. And I can do it with Star Adventurer GTi.

And that very mount appeared on the market already some time ago, and I did not notice it. It has a load capacity of 5kg, 180 teeth gear in RA, and 144 teeth in Dec. Communication is possible over WiFI and USB cable. There is a dedicated application available for smartphones and tablets with quite a lot of options. The illuminated polar scope is also there. Compartment for 8 AA-size batteries. Shutter release receptacle. SynScan hand controller (optional) input. ST4 port for guiding integration is there as well, of course.
And the best – the head weight is 2.6kg only. That is only 0.1kg more than regular Star Adventurer with wedge and declination dovetail!

The steel legs tripod is also included (another 2.5kg), but I plan to use my Benro tripod for travels, where each 0.1kg matters. For the same reason, the original 2.3kg counterweight will stay at home, and I will 3D print an empty counterweight, which I will with sand or gravel before use.

Star Adventurer GTi looks pretty stable, and the construction and solutions are thoughtful. But I do not expect anything less from the company that manufactures mounts for a long time already. Azimuth adjustment knobs are comfortable and quite long – provide a long range of regulations. The altitude knob is also well-designed. There is a backlash present in altitude regulation, but there are two locking bolts for altitude adjustment, so that is not a big problem. The polar scope cover is plastic and not quite tight. The polar scope itself is pretty standard, with adjustable illumination. All the receptacles and the main switch are on the back side that is not movable, so there will be no problem with cable dragging. RA axis clutch is a small bolt, and the Dec axis clutch is a large knob that you already may know from the regular Star Adventurer mount. The counterweight rod is massive with two fixing options – depending on the latitude you are. Vixen saddle is standard.
There is a cover on both sides of the back panel, and after removing it you will find a compartment for eight AA cells.

Communication with a Windows 10-based computer works fine – mount control from the dedicated application or any other via the ASCOM driver – all work just fine. Guiding with PHD2 as well. Both when connected via WiFi or USB cable.

But during my travels, Adventurer GTi will work with AstroLink 4 Pi device controlled by Stellarmate OS, and I performed my tests using this system. And for this system also everything worked well. If we want to use a WiFi connection we have two options available. By default, Adventurer creates its own wireless hotspot that you can connect to using the control computer. But the mount WiFi controller can also work in the client (station) mode and connect to the existing wireless network (like the home network or the one created by the AstroLink device). Connection with cable also works fine, and in the Ekos software, there are two options – SW Adventurer USB or SW Adventurer WiFi depending on the way we want to connect to the mount.

Both axes in Star Adventurer GTi are rotated with DC motors with encoders and an integrated gearbox. Motors are a bit loud during GoTo, but silent when tracking. Power consumption is very low, and that is good news for battery-powered setups.

After unpacking I checked the backlash in both axes. There was almost no backlash in declination and minimal backlash in the right ascension axis. Worm gear backlash regulation in Adventurer GTi is very straightforward. RA adjustment bolt is under the label on the RA motor cover. Dec axis adjustment bolt can be accessed after removing the Dec motor cover (4 screws).
But I did not do any regulations for a moment and loaded the mount with a 4kg setup (which is 80% of the mount capacity) and move it all to the garden for a first light. The setup contained an Askar FMA230 telescope, 6×30 guide scope, ASI290MM guiding camera, piggybacked AstroLink 4 Pi, and QHY268M main camera with filter wheel.

Polar scope illumination is quite bright even on the lowest level, but it is still usable. After polar alignment with the polar scope I checked the alignment error in the Ekos software, and that was 6 arc minutes. Precise polar alignment using Ekos took three minutes. That level of accuracy is not required for GTi work, but I wanted to eliminate any other error sources during the tests.

The night was a bit cloudy, but I was able to collect ten 2 minutes frames of the Pleiades cluster. Guiding worked well, and the total guiding error was 1.5-2.0 arc seconds.

Guiding accuracy at 2 arc seconds level is these days required even for a medium size astrophotography setup. Current CMOS cameras have small pixels, and the pixel scale is low. Even a 300mm focal length imaging setup may have a pixel scale 2″/px. It may be a bit more for DSLR cameras which have larger pixels usually.

The next session was performed using a Player One Saturn-C camera with an IMX533 sensor. The setup weight dropped to 3kg, but there were no noticeable changes in the guiding accuracy. At low declinations near the celestial equator, guiding accuracy was about 2″, and closer to the north pole it was about 1.5″.  You need also to remember, that in simple 30mm aperture guide scope the star size is about 10-15″ (sometimes more), and even during optimal conditions the star position is calculated with a 1-1.5″ error. Multi-star guiding can help.

During the next session, I ran the Guiding Assistant tool to find out some numbers about Star Adventurer GTi. The periodic error is quite big – about 40″. That is quite common for Adventurers, unfortunately. I wish the manufacturer would add PPEC to this small mount which could be a real benefit to many clients. At 40″ value guiding is required for longer focal lengths or longer exposure times.
A quite large declination axis backlash was also detected. There is no visible backlash in the worm gear, and also a very small backlash in the external gears between the DC motor and the worm. So the origin of that backlash probably is in the internal DC motor gearbox, which is a bit unfortunate. Calculated Dec backlash is 3-4s at 0.5x guiding rate. I expect that is the same for the RA axis, but the backlash in RA is not that important. Despite that big backlash in Dec, dithering works reasonably well.

GoTo accuracy is good, especially when you use plate solve software.
Declared 5kg capacity seems to be real. 4kg setup caused no problems or worries to Star Adventurer GTi. Both GoTo and guiding worked well.

What I liked:

• construction and mechanics
• illuminated polar scope
• low weight
• guiding accuracy
• communication with WiFi and USB cables both in ASCOM and INDI

What I liked less:

• large backlash in declination DC motor internal gearbox
• large periodic error

And a few more images that were made with Askar FMA230 and Player One Saturn-C camera (without active cooling). Alnitak is 90 minutes of total exposure, M44 is 45 minutes, Medusa nebula is 60 minutes and M81 is 180 minutes. Subframes were one minute for each image.