The mount is the most important part of your astrophotography setup. While this is true, one should understand what mount best suits his/her needs.
Beginners and enthusiast astrophotographers on a budget often begin their journey to the stars using a star tracker, a lightweight and very basic version of full-grown computerized equatorial mounts.
Star trackers mostly aim at wide-field astrophotography with lightweight setups using photographic lenses and small refractors. And while they can deliver high image qualities, they lack the most advanced features such as the GOTO functionality.
Today, with the Sky-Watcher Az-GTI mount (not to be confused with the Az-GTE version), you can build a portable, fully computerized setup for astrophotography that could put to rest all other star trackers.
In this article, I will show you how to do just that.
Meet The Sky-Watcher Az-GTI
The Sky-Watcher Az-GTI mount has a maximum payload of 5kg, can be powered via 8AA batteries and is controlled via Wi-Fi from your smartphone or tablet.
For size and capabilities, it fits in the star tracker class of instruments, a class that includes the Sky-Watcher Star Adventurer PRO and the iOptron SkyGuider PRO, but with a twist.
The Az-GTI, in fact, is not an equatorial mount as the other trackers, but an alt/az mount with GOTO capability, intended for observation and planetary/lunar photography on the move.
To know more about the Az-GTI, have a look at our recent hands-on review.
But the mount description I gave before is just the front cover of a much more interesting and surprising book. How so? Well …
While not officially advertising the Az-GTI as a mount for deep sky astrophotography, Sky-Watcher did release a number of firmware updates to unlock (and improve) the use of the Az-GTI in equatorial mode.
Thanks to this firmware update, with a few accessories, you can use the Az-GTI also for deep sky astrophotography: pop the mount on a wedge and the Azimuth is now the Right Ascension, while the Altitude becomes the Declination.
Deep Sky Astrophotography With The Az-GTI: Image Samples And Gear
How capable is this mount for deep-sky astrophotography? Much more than what my editing skills would suggest 🙂
Here is the list of gear I usually use in combination with this mount:
- ZWO ASIAIR PRO computerized system
- ZWO Miniguide Scope 30 F4 and ASI224MC for guiding
- ZWO ASI183MC and Olympus OM-D EM5 Mkii as imaging cameras
- Samyang 135 f/2, Sky-Watcher Evoguide 50ED and Celestron C5;
- Optolong L-PRO and L-Enhance filters
- 1kg or 2kg counterweight
Tracking performances when guiding are excellent: I could easily shoot for 300s or more with the Evoguide 50ED, and I have been pushing the mount up to 180s with the Celestron C5.
Alt/Az Vs. EQ Mode: What Is The Difference?
An Alt/Az mount is usually leveled with the ground and it follows the target in movements in Altitude (up and down) and Azimuth (left and right).
This makes the use of an alt/az mount very simple and intuitive, ideal for observing.
An Equatorial Mount, on the other hand, needs to be aligned to the celestial pole so as to move the telescope along the same circular path the stars follow while revolving around the celestial pole.
With respect to an alt/az mount, setting up an equatorial mount is a bit more tedious as you need to perform the polar alignment.
But by aligning the mount to the celestial pole, your long exposures will not suffer from field rotation, i.e., the rotation of the target in the field of view of the instrument, typical of alt/az mounts.
And even if popping an alt/az mount on a wedge and aligning it to the celestial pole will nullify field rotation, the motors will continue tracking the target in steps, often creating larger and/or odd-shaped stars.
Luckily for us, the equatorial firmware changes the way the motors work when selecting the equatorial mode, avoiding tracking issues.
How To Instal The New Firmware For The Equatorial Mode
It is fairly easy to update the firmware of the Az-GTI. At the time of this article, the latest firmware to add the equatorial mode is the AZGTi Mount, Right Arm, AZ/EQ Dual Mode, Version 3.32.
To install it, you need to download the Motor Controller Firmware Loader – WiFi, Version 1.76, which, unfortunately, is only available for Windows.
To update the firmware, follow these steps:
- Download and uncompress the zip archives of the Firmware Loader Wi-Fi and of the desired Firmware version
- Turn on the Az-GTI and wait for the wi-fi network to be created
- Connect your computer to the Az-GTi wi-fi network
- Launch the Firmware Loader
- Select the Firmware you want to load on the Mount and click on Update
- Wait for the loader to finish his job and when prompted turn off the mount
You can read more details on the procedure (also for Mac users) on this post on my blog or have a look at the video below.
From now on, when you connect to the mount using the Synscan Pro app, you will need to choose which mode you want your mount to run with: alt/az or equatorial.
If you use the alt/az mount, remember the telescope must now be mounted on the right side (you being behind the telescope).
Shopping List: Required Accessories
To use the Az-GTI as an equatorial mount you need a few accessories:
- A latitude base (or wedge);
- A counterweight with shaft;
- A dovetail base to mount your camera or lens;
As a latitude base, you can buy the wedge for the Star Adventurer PRO and similar, or go straight to the fantastic but costly wedge from William Optics.
The wedge of the Star Adventurer Pro.
To keep the Az-GTI free to rotate in right ascension, you need either a taller dovetail or to replace the locking knob of the wedge with a smaller one.
For the counterweight needed to balance the payload in right ascension, the threaded socket in the mount is a metric M12.
The shaft of the counterweight set available for the Star Adventurer PRO has a metric M8 thread. You either need a M8 to M12 adapter or to craft a new shaft using a M12 threaded bar you can find at your local hardware store.
This is the bare minimum to use your Az-GTI in equatorial mode for deep sky astrophotography.
To fully unlock the Az-GTI potential, though, you need a guiding system and something like the ZWO ASIAIR PRO to control everything while keeping the setup portable.
Here is how I set my Az-GTI for deep sky astrophotography.
How To Polar Align The Az-GTI
Polar aligning an equatorial mount is arguably the most important step to ensure the best performances and image quality.
But while the Star Adventurer PRO & Co. comes with integrated or separated polar scope to allow precise polar alignment, with the Az-GTI you don’t really need one.
The new firmware, in fact, adds to the Synscan PRO app an Electronically Assisted Polar Alignment routine.
Begin by performing a Star Alignment to get the mount orientation and follow the app instructions. Refer to this post on Cloudy Nights Forum for more info.
Even easier is to use the ZWO ASIAIR PRO or Sharpcap on a computer. As they can plate solving an image, there is no need to perform a manual star alignment. Simply point the mount (and the camera) toward the celestial pole and follow the instruction from the software to achieve the polar alignment.
Using an Electronically Assisted Polar Alignment routine is a big advantage over the use of an optical polar scope, particularly in the Southern Hemisphere or if you cannot see at all the celestial pole.
Please note that the Az-GTI is mounted on the wedge in the opposite way of the Star Adventurer: i.e., with the bubble level atop the mount pointing to the celestial pole.
How To Control The Az-GTI
Controlling the mount can be done by connecting your smartphone or tablet to the Wi-FI created by the mount and using the free Skywatcher Synscan app, available for iOS and Android devices.
Framing and tracking is done by performing first a star alignment to let the mount know how it is oriented, then use GOTO to frame the target. It is quite a basic interface but good enough if you are using a DSLR/mirrorless camera for your photography.
When you get more advanced and start thinking about guiding, you need your laptop or raspberry computer such as the ZWO ASIAIR PRO.
The connection to the mount can be done either via Wi-Fi or, better, with an eqmod usb cable (with a RJ11 connector) connected to the hand controller port of the Az-GTI.
By combining plate solving and goto, you can easily find your target and photograph it during multiple nights. Mosaics are also easily done.
Az-GTI Vs Star Adventurer PRO: Which One Is Better?
I have both these mounts and I was a great fan of the Star Adventurer PRO.
Compared with getting the Star Adventurer PRO, a basic equatorial setup built around the Az-GTI will cost you about the same or a little more.
But the Az-GTI will soon call for a better computerized system than the Synscan PRO App, meaning you may need a larger budget to begin with.
The biggest plus I see today for getting the Star Adventurer PRO over the AZ-GTI is that it forces you into understanding and solving astronomy-related problems:
- What does it mean to Polar align with a reticle?
- How do I manually find my target in the sky?
- What do terms like right ascension, declination, local standard time meridian mean?
Tip: the answer to those questions (and more) is in my Ultimate User Guide To The Skywatcher Star Adventurer PRO.
Being a fully computerized system, using the Az-GTI will force you to solve issues that are more pertinent to IT than astronomy (connection protocols and interfaces, etc.).
In the long run, though, once you consider you will get into guiding (dual axis in the case of the Az-GTI, in right ascension only for the Star Adventurer) and use a dedicated astro camera, the Az-GTI is a far better option than the Star Adventurer PRO.
In this article, you can read more about the PROS and CONS when comparing the two mounts.
The Az-GTI is the ultimate portable astrophotography mount for the enthusiast observers and astrophotographers out, offering outstanding flexibility.
Observation and planetary/lunar astrophotography are a “no-brain,” thanks to the alt/az and the GOTO. And the enthusiast deep-sky astrophotographers will be happy to find, among the rest, a dual-axis guide and GOTO capabilities.
To date, the az-gti is arguably the best mount in its class.