Jul 19

First Light – iOptron GEM28

Finally clear sky for the next few days… still small clouds but the conditions yesterday were good enough to test my new iOptron GEM28 mount.

I know the dovetail solution with the EOS 70D, EF 400mm and guidescope side-by-side is not ideal regarding balance… Unfortunately I’ve no other possibility to attach my equipment right now.

Setup & Polar Alignment

It took a bit more time to setup everything compared to the SkyWatcher Star Adventurer setup. But all in all the build-up was still done very quickly.

First I aligned the tripod and the GEM28 head (already in 47° position) towards North, until Polaris were visible in the polar scope. The built-in bubble leveler is handy to level the tripod.

Next I attached the dovetail bar (which I used on the Star Adventurer) with the Canon EOS 70D, EF 400mm and the guide scope on it and balanced everything as good as possible…

I started the polar alignment in zero position: counterweight downwards and scope/lense towards North respectively Polaris – as on the image to the right. The process is the same as with the Star Adventurer. For 30-40 minutes I periodically check Polaris’ position while the mount is powered off respectively while the motors are powered off.

I wanted to see Polaris in the polar scope, in the LiveView of my DSLR and hopefully also on the MGEN screen at the same time. After a few corrrections everything was alright! Polaris were visible on all 3 devices 🙂

Go-To Alignment and focussing

Since the polar alignment was already done and my DSLR pointed directly to Polaris the first One-Star alignment was quickly done. Vega was my alignment star.

To familiarize myself with the functions of the hand controller I also started a Two-Star alignment with Vega and Deneb. Again very fast done. I simply centered every star in LiveView mode on my DSLR and confirmed the center position on the hand controller.

It was magically, simply to select an object in the hand controller and let the mount do all the work! 🙂

GoTo NGC7000, back to Deneb for re-focussing and again back to NGC7000. Within seconds… That’s really fun!

I used Deneb to find focus with the Bahtinov mask. No shaking at all during focussing even if my fingers were on the focus ring! That’s fantastic!!!

First Exposures

These are my first unguided exposures @ 400mm, f5.6 and ISO1600, starting 22:30h CET during Nautical/Astronomical twilight:

90 seconds unguided seemed to be too much. Maybe some shots would be usable but there would be definitely rejects.

MGENII AutoGuiding

Unfortunately guiding was not successful! I need more time to experiment with all the settings and do a firmware upgrade first… my current firmware is 2.42, but there is 2.61 available.


Apart from the guiding error I’m very satisfied with the iOptron GEM28 so far! A new level of sturdyness compared to the Star Adventurer!

My plans for the next few nights:

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