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ES12'' Gen II Dobsonian


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Dear all,

Recently I purchased one of these dobsons from ES following the good critics I read in several forums.

The Gen II includes some improved features with respect to Gen I, 2 Nylon pad brakes, Virgin Nylon alt and azimuth support bearings (instead of plastic), counterweight bar included with a couple of 1kg counterweights, a classical ES dovetail for the finder.

Some of these improvements were demanded by Gen I users, and are highly appreciated, but there is still some minor improvements that the final user has to apply. I will describe them lately.

The set up is very fast, less than 15 minutes, though the assembly of the upper cage needs some patience the first times is done.  Regarding the optics, It is superb, though in my opinion the 75mm minor axis secondary is too big (other similar modes in that range use a 63mm one), it provides full illuminated views on my ES 100 degree eyepieces, the stars in the background seen in clusters like the NGC457 are astonishing.

The main mirror cell support is a mix of support concepts, a nine point mirror cell support with a couple of rubber wheels at 90 degrees, and 3 glued slings to the mirror laterals screwed to the back of the mirror cell support, provide lateral support for the mirror. The collimation as in Gen I is done from above in less than 5 minutes.

In the first light in semirural skies the views confirmed the good optics, as I said specially in star clusters the amount of stars which could be seen in the background increased with respect to my 200PDS, the globular clusters were literally smashed, and small planetary nebulae like M76 showed internal details.

Coming back to the cons, as in any Chinese made product there are quality problems not solved in this Gen II, the paint coatings from the secondary cage just jumped when I changed the position of the truss brackets.

When I tried to open the main mirror box for the first time, the scratched the yellow paint from the altitude bearings, a tolerances problem which I solved adding 2mm nylon washers between the altitude bearings and the mirror box.

More improvements to make on your own are to make a plywood cover to prevent moisture on the main mirror while waiting for the night, to put foam pipe covers around all the tubes, they make the winter usage of the scope more comfortable and at the same time help with the vibrations damping (which even with a heavy ES 20mm 100d EP where almost insignificant).

One more thing to add is a PWM motor controller, the fan only work at full speed, and there are so many nights when the temperature gradient does not fall fast and the fan speed can be left at a lower regime to save batteries.

In brief, the ES12'' Gen II, it is the Dobson truss scope with the lowest price in that aperture range, the optics is damn good, the mechanical improvement done in the GEN II, improve a lot the vibrations, and the movements of the scope, though a better control on the tolerances and the paint process should be done.

I attach some pictures taken at home and while the first light.

Cheers.

Mario.

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1 hour ago, Susaron said:

The Gen II includes some improved features with respect to Gen I, 2 Nylon pad brakes, Virgin Nylon alt and azimuth support bearings (instead of plastic), counterweight bar included with a couple of 1kg counterweights, a classical ES dovetail for the finder.

Nylon IS plastic.

1 hour ago, Susaron said:

In the first light in semirural skies the views confirmed the good optics, as I said specially in star clusters the amount of stars which could be seen in the background increased with respect to my 200PDS, the globular clusters were literally smashed, and small planetary nebulae like M76 showed internal details.

Not surprising  for a 12" ( 300mm ) mirror to show more than an 8" ( 200mm ) mirror.

Some interesting observations on this telescope that might help other owners.

Nigel

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Interesting report - thanks for posting it and the pictures :thumbright:

Sounds like ES have addressed some of the issues that the Gen I versions had. It would be nice if they provided no cost upgrades for those who bought Gen I ones :smiley:

Dobsonians always seem to be a bit of a "work in progress" out of the box.

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7 hours ago, John said:

Interesting report - thanks for posting it and the pictures :thumbright:

Sounds like ES have addressed some of the issues that the Gen I versions had. It would be nice if they provided no cost upgrades for those who bought Gen I ones :smiley:

Dobsonians always seem to be a bit of a "work in progress" out of the box.

oh damn me I lived in Bristol several months while working for Airbus and I was not aware about the astronomical society there .

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17 minutes ago, Susaron said:

oh damn me I lived in Bristol several months while working for Airbus and I was not aware about the astronomical society there .

It's been here since 1942 apparently. I only joined a couple of years ago.

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