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A Review of the 6-inch f/8 Sovietski Newtonian



In April of this year I took delivery of a 6-inch f/8 Newtonian reflector from Sovietski, the North American distributor of a line of telescopes manufactured in Novosibirsk in the former Soviet Union. I purchased the instrument with the intention that my 11 year-old son would "cut his teeth" as an observer with it, much as a classic 6-inch f/8 Criterion Dynascope served as my first telescope 35 years ago.

After reading a review of the instrument by George East that appeared in the December, 1997 issue of Sky & Telescope, I had some trepidation about optical quality. East reported that the example that served as the subject of his review had a smooth but spherical primary mirror (which he characterized as a 1/4-wave system; in fact, a 6-inch f/8 sphere is undercorrected by an unacceptable 1/2-wave at the final wavefront). Ed Ting repeated East's verdict of a spherical primary on his web site (www.scopereviews.com), although he did allow that "it really shows nice images." Curiously, a 1995 review of the instrument in the October, 1994 issue of the British magazine Astronomy Now had praised the instrument's satisfying performance on the planets, but a spherical primary of this aperture and focal ratio would have proved disappointing to anyone but a novice (and the reviewer, Adrian Ashford, was certainly no novice). My lingering reservations about the optics were more than offset by East's and Ting's enthusiastic remarks about the instrument's mechanical quality, so I proceeded with the purchase with the fallback position of having the primary properly parabolized by a good friend who is an experienced "glass pusher."

The instrument arrived packed in two massive, cardboard-sheathed, fitted wooden cases equipped with carrying handles. The exterior surfaces of these well-made boxes were covered with dents and gouges, presumably incurred while in transit from Siberia before being packed in cardboard stateside. Moreover, although the stamped steel corner protectors and the hinges were painted satin black, they showed a patina of rust. Don't expect heirloom-quality furniture! The larger case (which holds the optical tube assembly, pedestal column and legs, finder, and eyepieces) is so large and coffin-like that it requires two people to serve as "pallbearers." It just fits across the back seat of my Plymouth Neon, although not without scuffing the interior door panels.

The exterior of aluminum tube (unusually rigid due to its 2.5 mm wall thickness) is finished in gloss white enamel. Before flat black paint was applied to the interior of the tube, it was laboriously machined with parallel grooves that at first glance look like a fine thread of about 32 pitch. These grooves dramatically reduce glancing-angle reflections and give the instrument an usually high degree of freedom from stray light for a commercial Newtonian reflector.

As received, the telescope was poorly collimated. The elliptical diagonal mirror was a full 3/8-inch too close to the primary. Fifteen minutes with a screwdriver and laser collimator rectified this situation. The adjustable supports for both the primary and secondary mirrors are far superior to most examples in the market.

To evaluate the instrument's optical quality, I first increased the central obstruction to 33% by using a disk of cardboard taped to the hub of the spider, then examined the intra- and extra-focal images of alpha-Leonis per Dick Suiter's method. Low expectations are the key to happiness! Frankly, I was prepared to see evidence of substantial spherical undercorrection, but to my surprise and delight the spherical correction proved to be excellent. I replaced the eyepiece with a 133 line/mm Ronchi grating from Orion Telescope Center and carefully adjusted the focuser. Even two bands remained straight as an arrow! Optical quality was exceptionally good. At least in my unit, the primary mirror is not a sphere but a fine parabola.

I recently mentioned my favorable evaluation of the optics in a casual e-mail communication with my old friend Markus Ludes, the proprietor of APM telescopes (Reifenberg, Germany), the distributor of these telescopes in Europe, (where they are sold under the brand name "TAL"). He related that "many of these TAL optics are of fantastic quality" and that the performance of some 6-inch TAL Newtonians can rival that of a decent 130mm apochromatic refractor.

Unfortunately no planets have been visible, but on two consecutive evenings of unusually stable seeing the 9- and 10-day old Moon proved to be a very rewarding target. Four craterlets were visible on the floor of the crater Plato, where the "double craterlet" was easily resolved. Terracing on the inner ramparts of Copernicus was beautifully seen, even when the magnification was pushed to over 400X. If you have hesitated to buy one of these 'scopes because you have been led to believe that the optics are only so-so (as I was), you should hesitate no longer based on my experience!

A few ancillary remarks follow:

1.) As other reviewers have remarked, the quality of the 8X50mm finder is outstanding. Its Plossel eyepiece has an integral helical focuser and excellent eye relief; the glass reticle is in the form of a crosshair with an open center. Image quality is superb. This is a far better finder than the unit supplied with many telescopes selling for ten times the price (like my C-14's!). The finder's dovetail support bracket is also finely crafted.

2.) The rack-and-pinion focuser is well above average in quality, smooth in operation, and features adjustable tension. Loose tolerances between the rack and the broached keyway in the focuser's base casting do result in a bit of torsional twist, however. 1.25-inch format eyepieces are held by a thumb screw that bears against a black plastic clamping ring, a very nice feature. However, the bore is unnecessarily large and the fit will be a little sloppy until pressure is applied by the clamping ring.

3.) Three eyepieces are supplied with the telescope, a 42mm Kellner, a 25mm Ploessl, and a 15mm Kellner, as well as a 4X Barlow. The 42 mm Kellner is utterly useless. The surface of its field lens is coincident with the focal plane, so every mote of dust is glaringly obvious. To add insult to injury, the apparent field of view is less than 30 degrees, so the actual field of view is no larger than the one you enjoy with the 25mm Ploessl. The 15mm Kellner is decent -- competently made, but just too tight on eye relief for my tastes. The tack sharp 25mm Ploessl, however, is a real "keeper." One of the finest eyepieces I've ever used, it has beautiful coatings and excellent eye relief, comparing very favorably with a 25mm TeleVue Ploessl and a 24mm Celestron Ultima. The Barlow, a cemented doublet, also gets a "thumbs down." It has a very restrictive aperture and throws obtrusive ghost reflections becauset the edges of its lens elements are not painted flat black. The cement between the lens elements in my example had begun to separate.

4.) The pedestal is rock solid, although locating the captive spade-head bolt in each leg with the corresponding threaded hole in the column is a time-consuming and frustrating exercise that makes me exhibit symptom's of Turrette's Syndrome every time I repeat it! It is noteworthy that the equatorial head can be effortlessly rotated 360 degrees in azimuth relative to the pedestal, a very handy feature when aligning the polar axis on the celestial pole. Although the plastic feet at the end of each leg have been widely touted as a "vibration damping pads," they're far too rigid to perform this function.

5.) The equatorial head is quite well made, but did require some adjustments. When received, the friction clutch of the worm gear of the Right Ascension drive was tightened to the point that the assembled instrument couldn't be rotated on this axis without applying considerable force. This was easily rectified by backing off the three adjusting screws with a screwdriver inserted through a clever door located in the drive housing. The manual override of the drive is quite stiff no matter how carefully its separate friction clutch is adjusted. The manual tangent arm slow motion on the declination axis consists of a fine pitch screw that bears on a "tongue" of metal with a captive spring on the opposite side. This is the same design that was employed in the once-prestigious Unitron refractors. In my specimen, the hole in the casting that carries the threaded knob was poorly drilled and tapped, resulting in a bit of play that is certainly not inherent in this excellent design.

With a current price of $649.00, I consider this instrument to be an excellent value despite its quirks. Assuming that my unit's optical quality is typical of the breed, it should convincingly outperform any 4-inch refractor and give the average 5-inch refractor a real run for its money. The overall construction is very labor-intensive, increasingly rare in this day and age. Once the Russian economy achieves a modicum of health, don't expect quality like this to remain so affordable!



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