William Optics GTF81 5-Element 81mm APO Imaging Refractor Telescope - F81GTA

William Optics   ——   SKU: WIL-A-F81GTA
$1,321.29 CAD
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Product Info

William Optics GTF81 5-Element 81mm APO Imaging Refractor Telescope


  • This William Optics GTF81 APO Imaging Refractor has an air-spaced five element objective (FPL-53) in two groups, in an adjustable CNC machined ultra high precision lens cell
  • This objective is extremely sharp with excellent color correction for imaging or visual applications
  • Each lens is Fully Multi-Coated with a special super-high transmission coating (STM Coatings) on all surfaces
  • This F/6.6 objective lens is ideal for astrophotography

    The stunning new William Optics GTF81 APO Refractor telescope is the new jewel of the apochromatic refractor world. From the pristine white finish on the CNC machined tube assembly to its elegant red highlights, it sports a beauty which is more than just good looks... The new GTF81 features 5-elements in 2 groups designed using high-quality FPL-53 extra-low dispersion glass that reduces any secondary spectrum to an unbelievable degree. The second group of ED elements (which is a field flattener) provides an image field flatness to the maximum quality (covering up to a 40mm diameter image circle).

    A 2" & a 1.25" adapter are included in the price of this GTF81 APO Refractor Telescope from William Optics. It sports anti-marring brass compression rings to hold your eyepieces or accessories. The scope includes a carrying handle with a V-shaped night glowing illuminator. A Guiding Scope is an optional accessory as are 90mm mounting rings.
    This telescope has a 2-year warranty from William Optics.

    The WO GTF81 5-Element 81mm APO Imaging Refractor Telescope includes a 2" rack & pinion (R&P) focuser which will accept an optional Digital Display Gauge (DDG). The DDG (which is an option) allows you to take precise focusing readings down to two decimals. Extra-smooth 360 deg. rotatable 2.0" R&P focuser has a 1:10 dual speed: a treat to use during astrophotography. It prevents image shifting! Comes with two locking screws on angled positions for heavy load applications. It has a large aluminum knob with installed thermometer and aluminum protection cover.

    Telescope Specifications:

    Aperture 81mm
    Focal Ratio F/6.6
    Focal Length 535 mm
    Objective Type Five element with FPL-53 Air Spaced (2 groups), Fully Multi-Coated, STM coatings
    Resolving Power 1.43 seconds of arc
    Limiting Magnitude 12.2
    Lens Shade Retractable

    2" 360° Rotating Camera-angle Adjuster, 1:10 fine focus Focuser Travel Length 3.15" (80mm)
    1.25" Adapter

    1.25" Adapter 2" Brass Compression Rings
    Field Stops knife edge Baffles
    Tube Diameter 90mm
    Tube Length 440mm Fully Retracted
    484mm Fully Extended
    Tube Weight

    3.7 kg


    Objective Lens Surface Finish Specifications:

    Scratches Width, not more, mm 0.025mm
    Total length, not more 1/4 of total lens diameter.
    Quantity no more 3
    Dots or spot points No more, mm 0.4mm
    Quantity, no more 3
    Accumulation of defects Limited area, mm 0.8mm^2
    Total area of scratches and points, no more, square mm 5.8mm^2