While I don't own an ES 12" F5 dob, I did spend some time viewing thru one in a dark sky location. Before I begin my review, I do like to search the net for optical tests that may have been performed on similar units. I did find an example of another 12" F5 ES mirror tested with interferometry and that particular sample didn't fare very well at all:
http://www.astroreflect.com/images/pictures/tests_out/mirror3.png
Nevertheless, I had access to a model and I decided to put it thru its paces. The owner took awhile to put it together and and perhaps that was due to his unfamiliarity with it but it seemed it just took a lot longer than it should. In comparison, I probably could have assembled and disassembled my 16" astrosystems truss dob a couple of times over by the time the guy had it up and running. Although collimating the scope is relatively easy since you do it from the front of the scope versus the rear, this isn't really an innovation and Stephan Collet Phd of Bakersfield California had perfected a similar system years ago. I'm partial to the more traditional rear to front collimation procedure but either will work quite well so that's a matter of personal preference.
While a shroud wasn't necessary under dark skies, you'd want to have one if neighbor's lights are a problem, and I feel it should be supplied with the scope instead being an option. But that's an issue you see with a lot of new scopes these days.
Balance is a potential issue as well and I'd recommend an optional counterweight accessory, especially if you frequently change heavy two inch eyepieces in the focuser like I do. That's a problem in many scopes, though. In contrast, the sticktion in my astrosystems dob allows me to changes eyepieces at virtually any useable angle without any counterweight necessary and that's a real convenience that I've come to take for granted. My previous Discovery 12.5?" truss dob had a similar balance problem with heavy eyepieces and that proved to be a pain in the butt, especially in cold weather environments.
Movement of the ES 12" truss dob was well-controlled overall and the unit seemed to have a heavier substantial feel to it and I liked it better than my previous 12.5" Discovery truss dob. The design of the ES model is quite good in comparison to similar sized scopes that I have used in the past.
The focuser works well and it, too, has a quality feel to it. I don't believe you'll find a real need to replace it.
Observing comfort, even at the zenith, is very good and motions around "Dobson's hole" are well controlled.
There appears to be a paucity of DSC systems available for these models at this time and I personally consider that to be a significant drawback but that, too, is an individual preference.
Now to the optical performance of the unit in question. My particular sample worked very well. It thru up a bright, contrasty image of the Cat's Eye nebula under high magnification. Globular clusters were well resolved and similar in appearance to that of a more expensive premium style scope. The star test didn't reveal any glaring errors but just a bit of under-correction. I didn't see any astigmatism, either. So both the primary and secondary were likely ok in this sample. Unfortunately, the planets weren't well-placed for observation so I can't comment about it with this scope.
I must say I liked the scope very much but this is, of course, a sample of one so take that into consideration when considering the purchase of a production scope...
http://www.astroreflect.com/images/pictures/tests_out/mirror3.png
Nevertheless, I had access to a model and I decided to put it thru its paces. The owner took awhile to put it together and and perhaps that was due to his unfamiliarity with it but it seemed it just took a lot longer than it should. In comparison, I probably could have assembled and disassembled my 16" astrosystems truss dob a couple of times over by the time the guy had it up and running. Although collimating the scope is relatively easy since you do it from the front of the scope versus the rear, this isn't really an innovation and Stephan Collet Phd of Bakersfield California had perfected a similar system years ago. I'm partial to the more traditional rear to front collimation procedure but either will work quite well so that's a matter of personal preference.
While a shroud wasn't necessary under dark skies, you'd want to have one if neighbor's lights are a problem, and I feel it should be supplied with the scope instead being an option. But that's an issue you see with a lot of new scopes these days.
Balance is a potential issue as well and I'd recommend an optional counterweight accessory, especially if you frequently change heavy two inch eyepieces in the focuser like I do. That's a problem in many scopes, though. In contrast, the sticktion in my astrosystems dob allows me to changes eyepieces at virtually any useable angle without any counterweight necessary and that's a real convenience that I've come to take for granted. My previous Discovery 12.5?" truss dob had a similar balance problem with heavy eyepieces and that proved to be a pain in the butt, especially in cold weather environments.
Movement of the ES 12" truss dob was well-controlled overall and the unit seemed to have a heavier substantial feel to it and I liked it better than my previous 12.5" Discovery truss dob. The design of the ES model is quite good in comparison to similar sized scopes that I have used in the past.
The focuser works well and it, too, has a quality feel to it. I don't believe you'll find a real need to replace it.
Observing comfort, even at the zenith, is very good and motions around "Dobson's hole" are well controlled.
There appears to be a paucity of DSC systems available for these models at this time and I personally consider that to be a significant drawback but that, too, is an individual preference.
Now to the optical performance of the unit in question. My particular sample worked very well. It thru up a bright, contrasty image of the Cat's Eye nebula under high magnification. Globular clusters were well resolved and similar in appearance to that of a more expensive premium style scope. The star test didn't reveal any glaring errors but just a bit of under-correction. I didn't see any astigmatism, either. So both the primary and secondary were likely ok in this sample. Unfortunately, the planets weren't well-placed for observation so I can't comment about it with this scope.
I must say I liked the scope very much but this is, of course, a sample of one so take that into consideration when considering the purchase of a production scope...
