Introduction: AZ GTE Polar Scope
The Star Adventurer is a great small equatorial mount for those who like to do astrophotography in remote places. It is pretty accurate, lightweight and can carry a very reasonable load. However, it suffers from some limitations:
- it's RA motor is only 6V, leading to a low torque
- it is not motorised on the DEC axis, meaning it can only "half" PHD2 guide
- it has no GoTo capability
Interestingly, Sky Watcher also produces another very portable mount, the AZ GTI. It is 12V powered, can be used either with Wifi or the SynScan hand controller and is fully compatible with PHD2 guiding. While this mount is primarily designed to be used as an Alt Az mount, it also has the possibility to be used as an equatorial mount, hence the semi official name of AZ GTE: the firmware can be flashed to enable this possibility and there is an M12 socket to fix an M12 rod to counter balance the telescope in equatorial mode. However, a major limitation is that, as opposed to the SA, the AZGTI has no polar scope, seriously limiting the precision of your polar alignment. So I devised 3 ways to polar align this mount:
- a very rough polar alignment with an iPhone
- a precise polar alignment with a NEQ5 polar scope
- a very, very precise polar alignment with a pole master
Please be aware that the last two methods imply drilling holes in your AZGTI and will most likely void your warranty. I cannot and will not be held responsible for any damage you do to your mount.
- An AZ GTI
- some parts from the star adventurer: in fact, you don't need to buy the star adventurer: you can find them as spares in your local astronomy shop:
- the counterweight (sold with the rod)
- the equatorial wedge
- the dovetail
- 40 cm of M12 threaded rod
- a M12 nut
- 2 M3x15 mm screws
- 2 M3 square nuts
- 2 M3 "butterfly" nuts
- 4 M4x12 mm screws
- 4 M4 nuts
- one M8 screw, 1 to 2 cm long with an hex socket head
- 2 148x14 mm stainless steel plates: you should be able to source them from your local hardware store, they are used to fix furnitures
- some 3D printed parts that you can find on thingiverse:
- some other 3D printed parts here included (both STL and fusion360 files are provided)
Step 1: Flash the Firmware
Download the latest version of the AZ GTE firmware. You should find it on their website in the "support" "motor controllers" section. You should also download a firmware loader, either the standard or the wifi one.
If you have a SynScan hand controller, use the standard one. It is always preferable to flash the firmware through an USB connection than through WIFi since it is much more stable. Some users have reported significant issues with the Wifi Firmware flasher, so take your time and follow the instructions very carefully.
You should also take the opportunity to upgrade the firmware of your SynScan hand controller to the latest version if you own one.
Step 2: Preparing the AZ GTE Mount
This is by far the most dangerous part of the mod. You really really risk destroying your mount if you are not careful.
- remove the plastic cover by unscrewing the 6 screws holding it. Also remove the battery back
- drill two 3 mm holes at the location shown on the picture, separated by 43 mm. The mount is made of aluminium, so drilling should be easy. For increased precision, you can drill first using a 2 mm drill bit
- carefully remove all the tiny aluminium bits that will have spread within the mount. Use a vacuum cleaner and double check that none are left otherwise you run the risk of shorting the circuit board
- put the 2 M3 screws in the holes, add the square nuts to the baseplate and screw everything tightly
- bonus: add some extra lithium grease to the gears
- screw back the plastic cover
- fix the dovetail to the base of the AZGTI head
- Fix the equatorial wedge to the AZGTI tripod
- Remove the m8 screw from the wedge and replace it with the m8 screw with hex head (the knob of the wedge is too large and will collide with the AZGTI head
Step 3: Preparing the Polar Scope / Polemaster
- slide the steel plates into the polar scope and pole master supports
- fix them with the M4 screws and nuts
- slide in the polar scope
- fix the polemaster to the star adventurer to polemaster adapter and screw it to the support
Step 4: Using
- First, position the AZGTI tripod and wedge facing south. Yes, I know, it is counter intuitive but due to the configuration of the AZGTI head you have to perform this 180° rotation
- Fix the iPhone Holder and do your basic wedge adjustment using the daytime mode of the Polar Scope Align Pro App
- Remove the iPhone Holder. Install the AZGTI head, screw it tightly
- Screw in the M12 rod, install the counterweight(s). Don't forget the M12 "toe saving" nut !
- Install your telescope and balance it
- Install the polarscope on the AZGTI head and tighten it using the butterfly screws. Polar align
- Remove it, install the pole master and perform your very fine polar alignment
Step 5: Version 2. Much Easier and Less Dangerous !
I re designed a version of this project. It is easier to build and less dangerous since the drilling is done on the plastic battery holder. I will post it as a new intractable.