5", 6" and 8" lenses
The achromat continues to offer an outstanding value in refractor optics. Our achromats are air-spaced doublets made from durable, weather resistant glasses of normal dispersion. Thermal stability of the achromat is superb with little to no change of figure during observing, even with changing temperature. Chromatic aberration is reduced to a minimum, allowing excellent definition and resolution. Powers of 100x per inch of aperature can be used to advantage, when seeing permits. Our achromats continue to offer outstanding performance at very reasonable cost.
The Refracting telescope being void of any secondary obstruction continues to offer the highest quality image possible in a telescope system. D & G refractors are far less sensitive to temperature changes and tube currents than are reflectors. The resulting crispness and contrast of image make the refractor ideal for high resolution lunar, planetary and double star work. Further, the refractor has for years been underrated as a deep sky performer. The high contrast refractor image yields a black sky background compared to the gray background usually associated with reflectors. Lastly, the refractor is almost maintenance free. No need for constant collimation and recoating of optical surfaces. If cared for, your D & G refractor will last almost indefinitely as is evidenced by the number of fine 19th century refractors, which are still in use today. If you don't currently own a quality long focus refractor you may be missing a whole new observing experience.
Air-spaced doublets mounted in aluminum cells. Our objectives are not mass produced. Each lens is individually hand figured. Each is guaranteed to reach the theoretical limit of resolution for its size. All are color corrected for the C-F visual range between 5000 and 6500 angstroms and are fully coated.
All D & G lenses, including the 5", are now mounted in push-pull adjustable cells. Many other companies offer only a straight non-adjustable cell or no cell at all! The adjustable feature allows you to align the optical axis precisely. The results are better images and a telescope that stays in collimation even through rough handling or constant transport. While this is a more costly method of mounting the lens, the benefits should be readily apparent. All prices include shipping and insurance in the continental US.
Larger sizes (up to 20") and longer focal lengths are available, prices on request. Coating of 8" and larger lenses available at additional cost. 8", 10" and 12" at $275.00, $500.00 and $750.00 respectively for all four surfaces with MgF2.
All D & G Achromat Objective Lenses Feature
New focal ratios available: F/18, F/20, F/25, F/30 in all diameters and at the same price!
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