After assembling the explore scientific 12" truss dob for the first time, I can see why it might take awhile to get it fully operational.
Explore Scientific provides two balance points for this scope. One set is said to balance 1/25" oculars while another set reportedly balances a paracor and/or 2" oculars.
I set my scope to balance with latter but it would only balance with the former, making counterweights necessary for the heavier 2" eyepieces. The reason it won't balance with 2" oculars or with a paracor is that ES has made a revision to the focuser by adding a screw-on extension to it so that it'll focus with various eyepieces. This moves the heavier 2" eyepieces even further away from the structure and hence the need for a counterbalance. Apparently, even with the large long focuser and extension, the revision is definitely necessary as my 2" ES 9 mm 100AFOV eyepiece would barely come to focus even with the revised extension so either the truss tubes are to short or the mirror has a slightly longer focal length than F5. Since I didn't have counterweights available, I resorted to using 1.25" eyepieces for first light in my scope. ES also provides two teflon-tabbed hocky-pucks which allows for additional clutch tension on the scope but they don't help much in the case of 2" eyepieces. The supplied red dot finder is essentially useless and can't be aligned with the scope so I had to sight from the rear of the rocker box in order to find an object.
I utilized an Orion 25mm ultrascopic eyepiece as my finder eyepiece and once I managed to find an object with my crude sighting arrangement, I switched over to an ES 6.7mm 82AFOV eyepiece for more power and ease of tracking. First object up: Jupiter. I had keen interest for observing it for two reasons. First, I wanted to see Jupiter's moons appear has sharply defined tiny dots and, thankfully, that's what I observed. Ditto for nearby stars. The main aberration I find to be objectionable, and I'm in complete agreement with Tom Delay on this one, is astigmatism. It causes oval or ovoid images and prevents a sharply focused image at the wavefront. It just plain sucks and totally mucks up the view. In my sample, as well as in another that I had previously reviewed, it appears ES has got the stig out of their scopes, if these two 12" models are any indication of QC. The second reason for observing Jupiter was to observe the contrast between the belts and bands on the planet. I was surprised to see some decent contrast and detail in moments of good seeing. I had a reasonable view of Saturn as well but, again, my main concern was making certain the moons appeared as sharply defined pinpoint dots and nothing less.I'd say most serious observers probably wouldn't buy a 12' F5 reflector as their principal planetary scope so even if the optics aren't well-corrected, you're less likely to notice much of a difference on DSOs. This brings me to the star test. I checked Spica and Arcturus and although the intrafocal pattern looked quite good, the extrafocal pattern appeared less so but I couldn't get a clear view of the latter as it appeared to be boiling due to seeing conditions. I didn't have the fans up and running so I'll have to repeat the test on a later date with better seeing conditions.
My overall impressions of this scope are generally positive and the unit looks "cool" too! I tend to think of it as a modern revisionist recreation and evolution of the 70s/80s Coluter dobs that I've seen in the field. Reasonable photonic obtainment for the masses!
Somebody once said the 12" scope is the smallest of the big scopes and they're right. A 12" F5 scope can pack quite a potent punch under dark skies. I'd anticipate this one doing the same plus it's easy to store and transport.
I'm currently mulling an offer from Randy at Astrosystems to act as a prototype for his DSCs. I need to get more info from him. I like the sky commander computer and that's what he employs on his scopes. More on this later...
Explore Scientific provides two balance points for this scope. One set is said to balance 1/25" oculars while another set reportedly balances a paracor and/or 2" oculars.
I set my scope to balance with latter but it would only balance with the former, making counterweights necessary for the heavier 2" eyepieces. The reason it won't balance with 2" oculars or with a paracor is that ES has made a revision to the focuser by adding a screw-on extension to it so that it'll focus with various eyepieces. This moves the heavier 2" eyepieces even further away from the structure and hence the need for a counterbalance. Apparently, even with the large long focuser and extension, the revision is definitely necessary as my 2" ES 9 mm 100AFOV eyepiece would barely come to focus even with the revised extension so either the truss tubes are to short or the mirror has a slightly longer focal length than F5. Since I didn't have counterweights available, I resorted to using 1.25" eyepieces for first light in my scope. ES also provides two teflon-tabbed hocky-pucks which allows for additional clutch tension on the scope but they don't help much in the case of 2" eyepieces. The supplied red dot finder is essentially useless and can't be aligned with the scope so I had to sight from the rear of the rocker box in order to find an object.
I utilized an Orion 25mm ultrascopic eyepiece as my finder eyepiece and once I managed to find an object with my crude sighting arrangement, I switched over to an ES 6.7mm 82AFOV eyepiece for more power and ease of tracking. First object up: Jupiter. I had keen interest for observing it for two reasons. First, I wanted to see Jupiter's moons appear has sharply defined tiny dots and, thankfully, that's what I observed. Ditto for nearby stars. The main aberration I find to be objectionable, and I'm in complete agreement with Tom Delay on this one, is astigmatism. It causes oval or ovoid images and prevents a sharply focused image at the wavefront. It just plain sucks and totally mucks up the view. In my sample, as well as in another that I had previously reviewed, it appears ES has got the stig out of their scopes, if these two 12" models are any indication of QC. The second reason for observing Jupiter was to observe the contrast between the belts and bands on the planet. I was surprised to see some decent contrast and detail in moments of good seeing. I had a reasonable view of Saturn as well but, again, my main concern was making certain the moons appeared as sharply defined pinpoint dots and nothing less.I'd say most serious observers probably wouldn't buy a 12' F5 reflector as their principal planetary scope so even if the optics aren't well-corrected, you're less likely to notice much of a difference on DSOs. This brings me to the star test. I checked Spica and Arcturus and although the intrafocal pattern looked quite good, the extrafocal pattern appeared less so but I couldn't get a clear view of the latter as it appeared to be boiling due to seeing conditions. I didn't have the fans up and running so I'll have to repeat the test on a later date with better seeing conditions.
My overall impressions of this scope are generally positive and the unit looks "cool" too! I tend to think of it as a modern revisionist recreation and evolution of the 70s/80s Coluter dobs that I've seen in the field. Reasonable photonic obtainment for the masses!
Somebody once said the 12" scope is the smallest of the big scopes and they're right. A 12" F5 scope can pack quite a potent punch under dark skies. I'd anticipate this one doing the same plus it's easy to store and transport.
I'm currently mulling an offer from Randy at Astrosystems to act as a prototype for his DSCs. I need to get more info from him. I like the sky commander computer and that's what he employs on his scopes. More on this later...
