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About the Sky-Watcher AZ-GTI mount, 



    
        

            Ben

About the Sky-Watcher AZ-GTI mount

Description

I am testing my new mount : the Sky-Watcher AZ-GTI GoTo mount.
I am sharing here my setup and my first tests.


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What I was looking for...
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- replacing both the Vixen Polarie mount and the Star Adventurer mount in one unique mount
- 2 motorized axes for easy motion, panoramas, 2 axes guiding...
- GoTo for targetting more easily small objects
- portable
- easy powered

At first sight the AZ-GTI is an alt-az mount so not suitable for photography.
Sky-Watcher has released a firmware to turn the mount into an equatorial mount.
The firmware was experimental at the beginning but now it seems to be a stable release. I thought it was the right moment to jump into new experiences.


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Hardware (DSO setup)
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- the AZ-GTI mount + tripod + extension tube (all this is in the full package)

- an equatorial wedge for easy polar alignement. You can use the Star Adventurer one.
Mine : link
[UPDATE] the chinese wedge was not very strong. Some play in it. I decided to upgrade to the William Optics wedge. Expensive but strong and very pleasant to use (link).

- a polar scope, attached in the blue support : link
There is no illumination so I can not see the reticle. Not needed for now in my process.
[UPDATE] I do not use the polar scope anymore in DSO setup. Sharpcap is enough.

- counterweight
     * shaft + counterweights : link
     * additionnal counterweight : link

- dovetail plate : link
The SA plates also works.
For simple setup (shooting milky way) I will use the SA ballhead adapter : link

- Samyang 135mm + ASI183MM Pro + ASI to Sony E mount adapter
adapter : link
[UPDATE] Now I use ASI183MM + ZWO Electronic Filter Wheel (small one) + Canon Samyang 135mm + adaptors.

- Datyson T7c camera (ASI120 clone) + 32mm guidescope
     * guide scope : link
     * pan/tilt head : link
NB : the guide scope may be better attached, using less weight (the pan/tilt head is heavy) but for now it does the job :)

- focusing
     * I will use my DIY motorized focuser (link)
     * for the tests I have used a follow focus ring : link

- powering : from the manual it runs at 12V and it draws 750mA.
I have measured the power consumption with a multimeter : when tracking the mount draws about 50 mA. When the motors move at the highest speed the peak is about 300 mA.
     * in the backyard a classic 12V wall converter will do the job
     * on the go :
          -- you can put 8 AA batteries inside the mount ; not very practical to charge 8 batteries but it may be useful one day
          -- I have successfully tested this 5V->12V/1A converter, plugged to a USB power bank : link
          -- of course a classic 12V power tank will fit. I have this one : link

- one PC running Windows 10, connected to the mount WIFI

- total weight on the mount is about 3.2 kg. The mount is rated for 5 kg.


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Imaging workflow (DSO setup)
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- polar alignement :
     * rough alignement with polar scope : just putting Polaris in the scope.
     * fine alignement : with Polar Align tool in Sharcap. Works great.
[UPDATE] Now i do not use the polar scope anymore when using Sharpcap. Going roughly manually while Sharpcap is solving is enough to be in the pole area.
- focusing : with Focus Assistant tool in Sharpcap
[UPDATE] I also focus by visually inspecting a star in the field, zooming at 400-600 %. With Samyang 135 at f/2.8 and 1.5 seconds exposure one can see if the star is focus or not.
- star alignement : with Sky-Watcher SynScan Pro app (PC or smartphone version).
[OLD] 2 stars alignment seems to be enough for this setup (FOV is 3.15° x 2.12°).
- targetting : with SynScan Pro app
[NEW] What i do now is :
* slew to target in SynScan, without doing star alignment
* take a picture with Sharpcap (~ 10 s)
* launch All Sky Plate Solver software, connect the mount, solve
* in SynScan, delete alignment model if any, click align with scan and go back in All Sky to sync
* disconnect mount in All Sky, slew to target again in SynScan
* If needed, repeat the steps before. For me one iteration is enough
- shooting : with Sharcap
- guiding : with PHD2


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Use cases and results
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Please note that these are my own first tests. This is not a complete review of what the mount can do.
For instance the tracking results could vary depending on the declination target.

- milky way landscape / timelapse setup : Sony A7s (unmod) + Samyang 24mm, tracked during 30"
     * minimal setup (no guide scope, small plate, no counter shaft / weight).
     * shot at f/2.8.
     * resolution : 72.1" per pixel.
     * looks no problem.
     * only rough polar alignment (Polaris in scope).

- milky way close up / landscape / DSO scape / timelapse : Sony A7s + Samyang 135mm, tracked during 30"
     * same minimal setup except that shaft and counterweight are needed !
     * shot at f/2.8.
     * resolution : 12.82" per pixel.
     * only rough polar alignment (Polaris in scope)
To be confirmed. Maybe I was lucky and a better Polaris position in scope would be needed (this would require illumination to see the reticule)
     * looks no problem, see pic D, close up in pic E.

- DSO setup, unguided light version
     * no guide scope, no guiding camera.
     * shot with 12 nm Ha filter, gain 180, sensor temperature 28°.
     * focus not at the best in this test.
     * resolution : 3.66" per pixel.
     * polar alignement was "Excellent" in Sharcap.
     * autostretched images. Looks nice until 60" (see pic F and close up in pic G). At 90" there was some trails.

- DSO setup, guided
     * shot with 12 nm Ha filter, ASI178MM with gain 180, sensor temperature 27°.
     * resolution : 3.66" per pixel.
     * polar alignement was between "Fair" and "Good" in Sharcap => possible improvement here.
     * PHD2 displayed a warning message after calibration => possible improvement here ?
     * autostretched images.
     * North America, 4 minutes : looks fine. See pic J and close up pic K.
     * M31, 5 minutes : fine at 1:1 scale, pix L. However close up (pic M) shows not perfectly round stars.


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Pictures results
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M31
North America and Pelican
M45 / Pleiades


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Conclusion
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It's just the beginning but for now I am happy with this mount.
A few points :
     - It looks like a Star Adventurer with additionnal features.
     - Need more tests to see the possible exposure limits.
     - GoTo feature is very nice (and fun !). Endless plate solving for targetting is over ^^


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Useful links
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Tadej Skofic's YouTube channel (setup tutorials and results) : link
David Parks's review on using the AZ-GTI with different devices (Windows PC, ASIAIR, and Stellarmate) : link
David Parks's full setup with 73mm APO : link
Giant thread on Cloudy Nights : link

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netspoon
Ben
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    M

C

Description: polar scope support (blue part)

D

Description: A7s + 135mm, 30"

E

Description: A7s + 135mm, 30", close up

F

Description: ASI178MM + 135mm (3.66" per pixel), 60" unguided

G

Description: ASI178MM + 135mm (3.66" per pixel), 60" unguided, close up

J

Description: ASI178MM + 135mm (3.66" per pixel), 4 minutes guided

K

Description: ASI178MM + 135mm (3.66" per pixel), 4 minutes guided, close up

L

Description: ASI178MM + 135mm (3.66" per pixel), 5 minutes guided

M

Description: ASI178MM + 135mm (3.66" per pixel), 5 minutes guided, close up

Histogram

About the Sky-Watcher AZ-GTI mount, 



    
        

            Ben

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