Orion Premium 102mm f/7 ED refractor
SCS Astro Ltd. — +44 (0)1823 665510 — was £749
Written: ~5 years ago

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It seems only like yesterday that US-based Orion Telescopes and Binoculars started the current vogue for extra dispersion (ED) glass refractors with their 80mm f/7.5 apochromat. At around a third of the price of its high-end competitors, the little optical marvel was an immediate hit with its crisp images, proving that Chinese opticians had the skill to work ED glass into short focal ratio instruments that had equal or better colour correction than their traditional f/10 (and longer) predecessors. Orion subsequently released 100mm and 120mm aperture ED refractors, but realising that they needed to up the ante to stay ahead of the competition (principally William Optics), Orion recently introduced this Premium 102mm f/7 ED refractor.

The instrument is sold as an optical tube only, without eyepieces or finder. You also get a 20cm Vixen-style dovetail bar with a pair of heavy-duty tube clamps pre-drilled with a series of threaded mounting points for a separate guidescope, should you need one. Most observers or imagers in the market for a 'scope of this calibre are likely to already possess a quality mount (an EQ5 or larger is strongly recommended) and a full set of eyepieces, a star diagonal and finder. With regard to the latter, the Premium 102mm ED is equipped with a standard Synta-style dovetail base, so one has a number of finder options available. The 'scope arrives at your door in a single 65 x 23 x 23cm carton. From the various illustrations depicted online and in magazines you are already expecting it to be a well-crafted instrument in a classic white and black livery. What surprised me was that on closer inspection the white paint has a decidedly nacreous finish; in the sunlight it is a strikingly lovely refractor. At just over 8lbs for the bare optical tube, it also feels reassuringly solid to hold.

The 18cm long dewshield (surmounted by a metal dust cap, no less) is of a sensible length and extends with pneumatic precision, as one would expect it to. The multicoatings of the air-spaced doublet objective were without blemish and there are no foil spacers to introduce diffraction noise. Three internal knife-edge baffles and a flat black interior ensure excellent light sealing and contrast. My only criticism of what is otherwise a superbly engineered and smooth Crayford focuser is that the lock-down knob has to be clamped down unreasonably tight to prevent any movement of the drawtube. However, even without engaging the focuser lock no movement was detected with my alloy-bodied 2-inch dielectric diagonal and a William Optics UWAN 28 eyepiece (combined mass 1.5kg).

During tests conducted in January 2008 the 'scope delivered all that I expected of it. Using a range of William Optics UWAN eyepieces I was impressed with the symmetry of the intra- and extra-focal images, plus the collimation was perfect. At best focus, Capella displayed an unobtrusive secondary spectrum halo with two clean diffraction rings in moments of good seeing. Mars, just 13 arcseconds in diameter on the evening of the 24th, displayed a crisp limb with the Syrtis Major plainly approaching the planet's central meridian. Premium performance indeed. Recommended.