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This premium quality six-element zoom eyepiece can be used in any telescope that accepts 1.25" accessories. The knurled rubber grip is turned to change magnifications. All air-to-glass surfaces are fully multi-coated with proprietary Pentax SMC (Super Multi-Coated) anti-reflection coatings for high light transmission. For optimum contrast, in addition to the inside of the barrel being blackened, the edges of all lenses have also been blackened to eliminate any internal reflections within the lenses themselves. ED (extra low dispersion) glass lens elements that include Lanthanum glass are used to minimise chromatic aberrations and astigmatism. The result is very good contrast and center resolution, with very little ghosting.
A rubber eyecup twists in and out of eyepiece body to optimise your eye position and shield your eye from ambient light. When the twist-up rubber eyecup is fully retracted for eyeglass use, the eye relief ranges from 12mm to 18mm, depending on the focal length selected. This allows observers with eyeglasses to see the entire field of view at low powers, where the eye relief is 18mm, although some vignetting of the field occurs at higher magnifications. As you generally are looking only at smaller objects that do not fill the field at higher powers, the loss of some of the field edge due to vignetting is not usually a concern. The barrel of the eyepiece in marked in both magnifications (when used an 80mm Pentax spotting scope) and in focal lengths for astronomical observing. An index mark shows the power in use.
The zoom mechanism enables the observer to match the magnification to changing lighting or seeing conditions, which is one of the zoom eyepiece’s main benefits. Match that flexibility to Pentax-grade optics and you have an exceptional tool for any observer – terrestrial or astronomical. For astronomical use, the zoom is usable for medium to high power observing with telescopes of all optical designs – from long focal ratio refractors down to fast f/4.5 Dobsonian reflectors. The eyepiece is relatively heavy and physically large, so some care is needed in balancing free-moving astronomical telescopes (such as Dobsonians) when this eyepiece is in use.
JIS-4 weatherproof construction for protection against wet weather and night-time dew.
Mechanically and optically this is a benchmark zoom eyepiece!
Having owned several Baader 8-24mm zooms, and having always hankered after a premium Pentax one, I finally took the plunge in early 2016. FLO service was excellent, as always and I received the eyepiece 24 hours after ordering it.First impressions, (with all too few later sessions due to weather and work commitments):Size: This is a Big zoom, considerably bigger than the Baader, but looks fantastic and comes with branded eyeglass cover and bomb proof bolt case for storage.Build quality - superb, exemplary:Zoom mechanism is quite stiff, due to the O Seal JIS waterproofing, but it does ease off and I have found that the best results come when using a Baader Click Lock 1.25" adapter in my 2" scope focuser. This holds the ep rock solid and enables plenty of torque to allow the smooth rotation of the zoom mechanism. A real, tangible step up on the build of the Baader zoom.Optics: The optics are very, very good for a zoom. In comparison to a world class Meade Japan UWA 14mm, I would say the Meade ever so slightly edged it in terms of faint stars visible, but it was a very slight advantage: from darker skies than mine this might disappear as a factor, and a tiny price to pay for having several eyepieces in one unit.Stellar images are pinpoint to the edge in my F7.7 apo doublet, with very good contrast. Field of view. The range of this zoom is 24mm, at which the specs say the view is 38degrees, going up to the highest 8mm power, at which the view is 60 degrees. On the face of it, the 24mm setting is quite narrow, but it never feels tunnel like, and the quality of the views are excellent. I have a wide 68 deg 24mm for that purpose anyway, so I do tend to look at this (and Baaders are the same fov) as an 8mm-20mm eyepiece. At 20mm the field is approximately 45degrees, and at 16mm about 50 degrees (same as most plossls). But, unlike many cheaper fixed eyepieces, the whole field of view is very sharp right to the edge. At 14mm and above, the field increases steadily up to the very healthy 60 degrees at 8mm. And, of course, you can increase or decrease the magnification in very small increments/decrements as conditions dictate.The zoom is NOT 100% parfocal. As you move from the 24mm setting to the highest 8mm setting, you need about a 2mm further in-focus setting on my focuser to achieve perfect focus. This is not a deal breaker at all for me, but just something to be aware of.Perhaps the best feature optically of the Pentax zoom is it's versatility. On any given night the seeing can vary quite significantly, and, when using fixed length eyepieces it can be very tiresome to have to keep swapping eyepieces to get the best view at a given moment.With the Pentax, you just dial in the magnification that gives the best view, simple, with just one eyepiece. So, you can observe for longer and see more.This is not a cheap eyepiece. But, it is of superb quality in all respects, and will last you a lifetime if you want it to. The Baader is an excellent unit to be sure, but in my honest opinion the Pentax has it comfortably beaten on all counts. And, at about twice the price of the Baader, so it should!Highly recommended.
This is simply the best Zoom Eyepiece I have tried at longer than 6mm focal length. The field of view is good and sharp to the edges and the focal shift through the range from 8mm to 24mm is so small that I can't detect it at all. The construction is very sturdy and oozes quality.This lives up to the Pentax brand and although pricey at least backs it up with performance!
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