![]() ![]() Combined with the twist-up eyecup design, the long eye relief makes it a good choice for eyeglass wearers. It has a usable eye relief of 13mm, very good for an eyepiece in this focal length range. The six lens/four group design and two ED (Extra-low Dispersion) glass elements of the 12mm Astro-Tech Paradigm provides all of the optical virtues described at the top of this catalog page - high contrast, a sharp and flat field from edge to edge, excellent color fidelity, and exceptionally low astigmatism and barrel distortion. Its overall performance makes it a much better choice as a second eyepiece than merely doubling the power of most scopes' so-so standard 25-26mm eyepiece with a Barlow. This is an excellent magnification for planetary and close-up lunar observing, particularly when the high contrast of the eyepiece (rivaling that of orthoscopics and Brandons) is combined with its excellent color fidelity. ![]() On an 8" f/10 catadioptric, for example, it yields 167x. It is also quite remarkable for medium high magnification observing with long focal length refractors, reflectors, or catadioptric scopes. ![]() Its sharpness and lack of astigmatism across the field make globular clusters sharp, vivid, and nearly three-dimensional. Both fit nicely into its 1.67° field with the AT72ED, with a framework of black sky around the clusters to set them off. This is well suited for observing globular clusters such as M13 and M22. With the 430mm focal length Astro-Tech AT72ED, for example, its six lens/four group multicoated dual ED (Extra-low Dispersion) glass optics provide 36x and a field over three times as wide as the full Moon. With a short focal length refractor it is a low power eyepiece. (Rain, snow, or fog might limit its usefulness, however.) This medium focal length Astro-Tech 12mm Paradigm Dual ED eyepiece is usable with any telescope type, under virtually any seeing conditions - from fair to superb. Various Used and Demo Scopes and Mounts.Astro-Tech AT60ED and AT72EDII Black Friday Sale.Explore Scientific Nebraska Star Party Sale.Various Closeouts Meade, Kendrick, Bob's Knobs, JMI and others.Astronomics Used, Demo, Closeout, Spring Cleaning Page.Rechargeable Batteries And Power Supplies.Personal Planetariums / Electronic Sky Guides.Focal Reducer and Field Flattener Combos.Equatorial & Altazimuth Accessories & Adapters.I love the BSTs, but be aware that they, like any range, have a sweet spot of performance and it isn't the ones at the extremes of the product range. Yes, you get an ever so slightly bigger FOV, but if you don't get the object in the sharp centre of FOV in the first place, you may not see it at all. I've lost faint fuzzies in the edge of field atigmatism of budget EPs, which means the longer focal lengths aren't much more use than a cheap Plossl. I trained the 25mm BST and a 25mm SW Plossl on a distant roof and gained little more than half a roof tile in the FOV, but the SW Plossl was MUCH sharper edge to edge. The point I feel worth making here, is that that with budget EPs, you can be giving up a lot for a few extra degrees of FOV. The 5mm BST may have suffered from pushing the magnifiaction and therefore the resolution of the scope further, but I generally found I prefered the view through the 8mm TMB. There was little to separate them, but the slightly narrower FOV of the TMB 'designed' EP, was sharper across the view offered. Likewise, the 8mm was decent, but I prefered the edge to edge sharpness of the TMB 'designed' planetary, also available from STL. Fair play to a cheap EP in an F5 reflector, but with the 18mm, it was more like 10% - It was a big jump and I prefered the view through a £20 SW 25mm Plossl. Most of that holds true for the other focal lengths, but I found the 25mm suffered more from astigmatism on the outer 25% of it's field of view. They're not far off being parfocal too, which makes swapping from one to the other easier. The large objective makes them dead easy to view through, as does the eyeball friendly twist up eye cup. They offer near plossl clarity with a bit more FOV, a more consistent eye relief and superb build quality. In my experience, the BST/Starguider 12-18mm EPs are superb. ![]() The 2" EPs oferered by STL are something else altogether. Thanks in advance.The BST/Starguider EPs are a 1.25" lineup. It would also be useful to know if they are parfocal. So, if you have experience of any of them, how about writing a review? We would all greatly appreciate it. It seems that ED glass is used in them, so they should be good I think. I am very keen to know more about the BST eyepieces as sold by Sky's the Limit. ![]()
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