THE TAL 6X30 & 9X50 FINDER SCOPES By: William Paolini 2014

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1 THE TAL 6X30 & 9X50 FINDER SCOPES By: William Paolini 2014 Figure 1. TAL 9x50 Finder (top), Illuminator for 9x50 Reticule (center) 6x30 Finder (bottom) and Mounting Bracket for 6x30 Finder (lower right) I. Introduction TAL telescopes and accessories are made in Russia by Novosibirsk Instrument-Making Plant ( Typical of all TAL products, the 6x30 and 9x50 finders are solidly built and well designed. TAL astronomy products are available worldwide from multiple sources including: United States: Russia: United Kingdom: II. Physical, Mechanical, and Optical Examination Both the 6x30 and 9x50 finders are straight-through refractors, showing the image inverted and reversed. Two grooved metal bands are on the bodies so that mounting bracket set screws do not mar the finish on the body of the finder. These brackets can be repositioned to accommodate differing mounting brackets. The dew/light shields on both are made of hard plastic, and slip off the front and onto the eyepiece end of the finder for transport/storage. Objective and eyepiece caps are supplied with both.

2 The dimensions of the 9x50 finder is approximately 9.85" long without dew shield and 11.75" long with the dew shield. The main body is approximately 2.4" in diameter. For the Right Angle version, available for the 9x50 finder, the length without dew shield to the trailing edge of the diagonal is 7.7", with dew shield this length is 9.5". The 6x30 finder is approximately 6.75" long without dew shield and 8.25" long with dew shield. The main body is approximately 1.5" in diameter. Figure 2. TAL 9x50 in Right Angle version with Illuminator attached Image copyrighted by and courtesy of Objectives on both finders are beautifully coated and held secure with metal retaining rings. Figure 3. TAL 6x30 main objective (left) and 9x50 main objective (right)

3 Focusing for both is accomplished by rotating the eyepiece. The focusing mechanism on the eyepiece is smooth and precise on both finders. The eye cup on the 6x30 finder is hard plastic, whereas the eye cup on the 9x50 finder is soft rubber. Neither eye cup is adjustable. Figure 4. TAL 6x30 eye lens (left) and 9x50 eye lens (right) Cross hairs are clearly visible though each finder, regardless if observing during day or night. The cross hairs on the 6x30 finder are much thicker in appearance than those in the 9x50. The 9x50 finder has very thin cross hairs that can also be illuminated using the variable light emitting diode (LED) accessory. If the LED accessory is not attached to the 9x50 finder, then a metal cover plate screws onto the port to protect the reticule's illumination port. Figure 5. TAL 9x50 Reticule Illuminator unattached (left) and attached (right)

4 III. Field Observations Field observations with the TAL finders was conducted during the winter months of November and December 2013 from a suburban location west of Washington, D.C., USA. The 6x30 Finder The True Field of View (TFOV) displayed in this finder was very generous being more than 7º. In use the TFOV is large enough for both stars in Orion's shoulders (Betelgeues and Bellatrix) to very easily fit within the FOV. Similarly, both the entire Belt of Orion and Sword of Orion easily fit within the same Field of View (FOV). The Apparent Field of View (AFOV) of the eyepiece appears typical of a Plossl's AFOV, being approximately 50º. Like most finder scopes, due to their very fast focal ratios, it is rare to find the entire FOV sharp from edge to edge. The TAL 6x30 is no exception rendering star points very well across 50% or more of its AFOV. Past this point brighter stars began to lose their pinpoint appearance off-axis due to astigmatism. Being such a small aperture finder, Seep Sky Objects (DSO) are naturally a tougher find, especially from my suburban location which often has a limiting magnitude of only 4.0. However, even though challenged with the small 30mm aperture, I was still able to easily identify targets like the Perseus Double Cluster, even on an evening when the dimmest naked eye star was only magnitude 3.5! I was actually impressed that this little finder could still easily find the Perseus Double Cluster as in my light polluted skies small finders like this are often not that useful. However, the TAL finder's bright and high contrast optics proved up to the task. Focusing of the finder was easy and precise with no fogging issues encountered from either the objective or the eyepiece when being used in cold weather. Again, compared to other finders that sometimes need the objective end rotated or moved to achieve focus, this finder's eyepiece helical focusing method for this finder was more intuitive and ergonomic. Finally, the thicker cross hairs of its reticule, compared to the 9x50, was also a nice touch given the limited 30mm aperture making them always easy to see when locating targets. Overall, a very nicely executed finder scope with a very robust build, good optical performance, and pleasing ergonomics. The 9x50 Finder The TAL 9x50 finder, with its larger 50mm aperture, stronger 9x eyepiece, and larger eyepiece AFOV (measured at approximately 55º) was a joy to use. Like it's smaller 6x30 counterpart, it is robustly built and has a very smooth helical focusing mechanism on its eyepiece. Another critical difference with this finder, is the incorporation of a port to attach an illumination device to light up the eyepiece's cross hair reticule. The reticule in this finder differs from the 6x30's in that it employs exceedingly thin cross hair lines that also have hash marks at the 1/3rd and 2/3rd FOV positions. With or without the red LED's illumination, whose intensity can be adjusted by rotating the on/off knob, this reticule's thinly etched lines were pleasingly unobtrusive and never distracting or in the way of the stars or celestial objects being targeted.

5 Figure 6. TAL 9x50 Illuminated Reticule The TFOV of the TAL 9x50 finder scope, although not as large as the 6x30's, is still respectably large being approximately 5º+. In use, its TFOV is large enough to just fit the entire Belt of Orion and the Great Orion Nebula within its FOV. Like the 6x30 finder, the 9x50 also held sharp star points, but across a larger 60% or more of its FOV. Unlike the 6x30 however, the main off-axis aberration in the 9x50 was not astigmatism but only Field Curvature. As a result, the off-axis could be easily focused to sharp, or to a compromise focus position between the Field Curvature points where my eyes could accommodate enough of the Field Curvature so that 80% or more of the stars showed sharp across its FOV. Impressive performance. In the field, the 9x50 finder nicely framed the Pleiades Cluster showing its many bright stars wonderfully rendered against a dark background. Objects like the Andromeda Galaxy, the Orion Nebula, and the Perseus Double Cluster were all easy finds using the 9x50, even on evenings where the limiting magnitude was as little as 3.5. On darker evenings, the open clusters in Auriga were also a very easy find. The moons of Jupiter were even an easy observation with the 9x magnification of the TAL 9x50 finder. The lasting impression this finder left was that it felt more like I was observing with a binocular or a "real" telescope as its FOV was so bright and pleasingly detailed. When comparing the TAL 9x50 finder to the Orion 9x50 Right Angle finder, the Orion fell short on many levels. The objective end focusing of the Orion was not as precise or as easy as the helical focusing mechanism on the eyepiece of the TAL, the TAL's eyepiece with its larger 55º AFOV was much more comfortable to view through, and the TAL showed a larger TFOV making targets easier to find. And surprisingly, even though both the Orion and the TAL both have 50mm objectives, the view through the TAL was noticeably brighter. Overall, the TAL 9x50's much more robust build and improved optics made it feel and perform in a class well above that of the Orion 8x50 finder.

6 When comparing the TAL 9x50 to the very nicely appointed Explore Scientific 8x50 erect image straight-through illuminated finder, the view and build were more competitive. The Explore Scientific, like the TAL, is a very nicely built finder, with excellent fit, finish, and features. The first thing one notices when comparing the two in the field is that the Explore Scientific provides a smaller image scale but a more expansive 6 º+ of TFOV compared to the TAL's 5º+ TFOV. The AFOV of the Explore Scientific is also a larger 60º+ whereas the TAL's AFOV comes in closer to a 55º AFOV. However, with Explore Scientific s advantages in TFOV and AFOV came a few disadvantages. The longer eye relief of the Explore Scientific's eyepiece made eye positioning sometimes tricky, especially with there being no eye guard. The lower 8x magnification of the Explore Scientific was not able to show DSO as easily as through the TAL, and the Explore Scientific's view seemed to not be as bright as expected, probably due to the erect image prism robbing some light. Finally, the illuminated cross hair, while very nice in the Explore Scientific, did not have as fine of an illumination control as the TAL's, giving the TAL an advantage of a greater range of dimmer reticule illuminations than could be achieved with the Explore Scientific. With this mix of advantages and disadvantages between the two, at dark observing site I would probably lean more towards the Explore Scientific finder over the TAL given its more expansive TFOV. However, at typical suburban light polluted sites, the brighter view of stars against the darker background sky due in combination from the higher magnification and lack of a light robbing erect image prism gave the TAL a definite advantage, and made various DSO, even difficult ones, much easier to find from my suburban observing location. IV. Conclusion Overall, both TAL finders are solidly executed with robust build quality and very good performing optics, better than the competitors they were tested against. The removable dew shields, smooth helical focusing at the eyepiece, special rings on the housing to protect the finish when mounting, and very finely controlled optical illumination for the 9x50 are ergonomic plusses not often found on finder scopes. Both finders show very bright, high contrast views with easy operating mechanicals. And while the 6x30 performed better than with surprisingly bright images from its small aperture, the 9x50 stole the show -- its combination of a lager 55º AFOV, higher 9x magnification to more easily find DSO, sharp FOV, and precision illuminated reticule made this finder feel more like a small precision telescope rather than simply a bland finder scope. The option to get this superb 9x50 finder in either straight through viewing or right angled viewing is a very much welcomed added bonus. The TAL finders present a step above the typical for this often critical telescope accessory and would be very worthy additions to even high-end premium telescopes. ~ ~ This article is placed in the public domain with no restrictions when made available in its entirety. All images Copyright 2014 by William Paolini and require written permission if used apart from this article. For a formatted PDF version of this article, please contact the author at wapaolini@hotmail.com.