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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.
Having downsized to exclusively 1.25" eyepieces for financial reasons, I found myself missing widefield views. Recent price hikes mean the Ethos range are well out of reach, so I looked into alternatives.
First up on my budget list was Burgess Optical TMB 40mm 68 degree afov. I purchased this used last year and it is a very nice, relatively compact and lightweight eyepiece. In comparison with the grenade that is a 41mm Panoptic it is positively slender!
I've yet to use this under a dark sky where it would excel, but so far have used it to get a decent fov in my C925 from home and have been pleased with the results. I found this comparison with a 41mm Panoptic on line which makes interesting reading. I would be surprised if the differences were as marked as is described here. The description of a flat field also puzzles me, I understand it to be related to field curvature i.e. Where the focus point is consistent across the field, rather than related to increased magnification towards the edge. Any thoughts?
Next up on my list was a used 20mm Explore Scientific 100 degree. Last night was the first time that I had a good chance to use it, and I was pleasantly surprised. Looking at a variety of old favourites such as M45, the Double Cluster and other OCs such as M36, M44 etc, the contrast was impressive, sky background dark and star shapes consistent across the field. I guess the Tak at f7.4 is not a tough test, but these objects certainly looked great even under skies that were at best mag 19.35 on the trusty SQM.
Finally, I could not resist a new 30mm ES 82 degree. This has yet to have much of a run out except from the back garden, but I have every expectation that it will deliver good results. Hopefully I will get away camping to Dorset or Devon camping for a week or two this summer.
Effectively the 20, 30 and 40 go head to head with the 21mm Ethos, 31mm Nagler and 41mm Panoptic. It is curious why There is a 1mm difference in focal length across all of these eyepieces, given that the ES at least are pretty much direct copies I don't understand why they would differ? I'm sure that ultimately the Ethos range will have an edge under good conditions and in faster scopes, but for the moment I am content with what I have. I need to sort some foam for a case to put them in to add to the Show Us Your Eyepiece Case thread .
For my 16" Meade ACF F8, I'll be buying a Moravian G4-9000 camera with KAF-9000 chip.
The KAF-9000 chip is 36.7mm square, a big chip! on paper the Explore Scientific 3" 0.7 reducer/field flattener could work well right to the edge, but has anyone tried it with Meade ACF telescopes? Also, I'm wandering what is the light cone of the Meade 16" ACF F8, will I get a lot of vignetting with that chip? I have a friend who has tried a KAF-9000 with his Meade 12" ACF F8 with very acceptable results.
Thank you for your time.