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Astro-Tech - White 90mm f/6.7 FPL-53 ED Triplet Refractor Telescope


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Astro-Tech White 90mm f/6.7 FPL-53 ED Triplet Refractor Telescope


What makes the 90mm Refractor Telescope from Astro-Tech so special? The answer is the price. The optics that compose this telescope are very high quality, and yet the price is so reasonable. The FPL-53ED with a f/6.7 focal ratio is one of the first telescopes with these optics to be priced so low.

Astro-Tech has incorporated FPL-53 glass more frequently. Most other telescope designers tend to use FPL-51 glass (lower quality) in their designs, even more high-end ones. The White 90mm Refractor incorporates FPL-53 glass instead which although it is more expensive, the results created are exceptional. This glass excels at accurate light transmission and inhibiting color halos to create sharp views.

It doesn't stop here however, Astro-Tech has included awesome accessories with this this telescope. A 360° rotatable rack-and-pinion focuser dual speed gives the observor to place their eyepieces or astrophotography camera anywhere they want. For eyepiece secure mounting support, there's also 2" and 1.25" eyepiece holders with compression rings that won't scratch or damage them. Last but not least, that telescope is equipped with a retractable lens shade and aluminum-frame carrying case.




Apochromatic triplet refractor optics - 90mm (3.54”) aperture, 600mm focal length, f/6.67 focal ratio three-lens optical system using the finest quality FPL-53 ED (Extra-low Dispersion glass) element to reduce spurious color halos and fringing to vanishingly low levels. All three lens elements are made from the finest quality Ohara glass. Ohara is well-known as Japan’s premier manufacturer of specialized optical glass. The lens cell is fully collimatable for peak performance.


Fully multicoated optics - The triplet objective lens has the latest state-of-the-art antireflection multicoatings on all air-to-glass surfaces for high light transmission and excellent contrast. This can easily be seen by looking into the objective lens of the scope. Virtually no reflection of your face will be seen. It’s a sure sign that the high transmission coatings are doing their job, by letting virtually all the light enter the scope, rather than reflecting some light back to your eye.


Internal light baffles - Contrast-enhancing knife-edge light baffles in the lens shade and the optical tube provide truly dark sky backgrounds and high terrestrial contrast. The edges of the lenses are blackened to reduce internal reflections and further improve image contrast.


Dew shield - A self-storing retractable dew shield slows the formation of dew on the lens in cold weather to extend your undisturbed observing time. It also improves the contrast, similar to the effect of the lens shade on a camera lens, when observing during the day or when there is excessive ambient light at night, such as a neighbor’s backyard security light. The tube measures a very compact 21” long with the dew shield retracted, and only 24” long with it extended.


Dual speed microfine 2.7” rack-and-pinion focuser with 2” eyepiece holder and 1.25” eyepiece adapter, both with compression rings - The precision-made focuser has dual-speed focusing. There are two coarse focusing knobs. The right knob also has a smaller concentric knob with 11:1 reduction gear microfine focusing ratio. This provides exceptionally precise image control during high magnification visual observing and critical 35mm or CCD imaging. The focus knobs have ribbed gripping surfaces so they are easy to operate, even while wearing gloves or mittens in cold weather. The 2.7” focuser drawtube terminates in a built-in camera angle adjuster as standard equipment. It is not an optional extra-cost accessory, as it is with some other scopes. The camera angle adjuster lets you rotate the focuser to line up a camera in either a landscape or portrait orientation (or any orientation in between), as well as put a star diagonal and eyepiece into the most comfortable observing position. A knob on the camera angle adjuster lets you lock the focuser at whatever angle is most convenient for you. The extra-long 120mm (4.7”) travel 2.7” diameter focuser drawtube has a scale marked in 1mm increments so you can note individual focuser positions for easy return to the correct focus when switching between visual use and photography. A lock knob on top of the focuser lets you lock in your photographic focus. The 2.7” drawtube has a 2” eyepiece holder that uses a non-marring soft brass compression ring to hold a 2” star diagonal and accessories in place. The compression ring won’t scratch the barrel of your star diagonal and accessories as an ordinary thumbscrew can. A standard equipment 1.25” accessory adapter slips into the 2” eyepiece holder to let you use a 1.25” star diagonal or image erecting diagonal. Like the 2” eyepiece holder, the 1.25” adapter also uses a non-marring soft brass compression ring to hold 1.25” star diagonals and accessories in place. If you are partial to 1.25” eyepieces and need an outstanding diagonal for this scope, consider the Astro-Tech 1.25” dielectric diagonal (#AT1D 1.25" 99% Reflectivity dielectric mirror diagonal). It's a Sky & Telescope Hot Product for 2007. An Astro-Tech guaranteed 1/10th wave peak-to-valley accuracy 2” quartz star diagonal (#AT2DQ Astro-Tech One-piece machined 2" diagonal with 1/10th wave quartz mirror) is recommended to deliver all of the scope’s exceptional optical performance to your eye.


Tube finish - No tube rings are supplied for the 114mm o. d. optical tube, as some observers may already have rings for this popular tube size. If rings are needed, however, optional 114mm Astro-Tech #AT114R hinged tube rings are readily available.


Other supplied accessories - A slip-on metal dust cap is standard. There is a dovetail shoe on the upper left side of the optical tube for installing an optional multiple reticle red dot finder (#ATF).


Shipping/storage case - The scope comes in a foam-fitted aluminum-frame locking hard case with carry handle. Astro-Tech is one of the very few manufacturers to provide a case at no charge for protection during shipping and as a storage convenience when the scope is not in use. Unfortunately, FedEx, UPS, and the Postal Service are very good at treating packages roughly. Occasionally, your scope can arrive in perfect condition, but with the walls of the shipping case dented in transit from rough handling, or the aluminum frame sprung, rendering the appearance of the case less than pristine. Damage to the shipping case in such instances is not covered by warranty.


Two-year warranty - As an expression of the confidence Astronomy Technologies has in the quality of their products, the Astro-Tech AT90EDT triplet is protected by a two-year limited warranty against flaws in materials and workmanship (shipping case excluded).




Additional Information

Name Astro-Tech - White 90mm f/6.7 FPL-53 ED Triplet Refractor Telescope
Manufacturer Astro-Tech
Model AT90EDT
Aperture 3.54"
Focal Length 600mm
Focal Ratio f/6.67
Highest Useful Magnification 171x
Limiting Stellar Magnitude 12.3
Optical Design Apochromatic Refractor