ZENITHSTAR 81 F/6.9 APO DOUBLET
William Optics
Apochromatic doublet
3.53 kg
ZENITHSTAR 81 F/6.9 APO DOUBLET - Gold / OTA Only is backordered and will ship as soon as it is back in stock.
The William Optics ZenithStar 81 is a two element apochromatic refractor with a focal ratio of f/6.9 and a focal length of 559mm. Utilizing FPL-53 synthetic fluorite glass, this telescope provides excellent aberration correction.
The 2.5" 10:1 rack & pinion focuser is smooth, stable and reliable, providing no slippage over long imaging sessions. The new CNC-machined and anodized handle bar with finder-style saddle is perfect for attaching a guide scope or other accessories. The ZenithStar 81 also includes William Optics' innovative clear Bahtinov mask integrated into the lens cap.
For best imaging results, it is recommended to pair the ZenithStar 81 with its matching Flat6AIII 0.8x field flattener.
Note: As the Flat6AIII an adjustable flattener, you must adjust the distance for your specific telescope. See the Instructions tab above.
Specifications
| Optical design |
Apochromatic doublet |
|
Objective diameter |
81 mm |
|
Focal length |
559 mm |
|
Focal ratio |
f/6.9 |
|
Image circle |
44.3 mm (with Flat6AIII field flattener) |
|
Compatible flattener |
William Optics Flat6AIII |
|
Mount attachment |
210 mm Vixen-style/Arca-Swiss dovetail bar |
|
Focuser |
Rack & pinion dual speed (10:1) 2.5" diameter |
|
Camera connection |
M63 x 1, 2" |
|
Backfocus |
60.2 mm (with flattener/reducer) |
|
Tube weight |
3.53 kg (including accessories) |
|
Tube length |
460 mm (fully retracted), 560 mm (fully extended) |
|
Tube diameter |
TBA |
|
Dew shield diameter |
TBA |
|
SKU |
WO-A-Z81GD (Gold), WO-A-Z81RD (Red) |
Included items
- ZenithStar 81
- Lens cap with Bahtinov mask
- Finder saddle handle bar
- 210 mm Vixen-style dovetail bar
- Soft carry case
Instructions
Note: Once you have unscrewed the rear adapter to the appropriate value in the table below, the remaining backfocus distance to make up will be 55mm from the rear M48 thread.
Distance adjustment needed for correct backfocus
| GT71 |
9.1 mm |
|---|---|
| GT81 |
7.1 mm |
| Z81 |
5.2 mm |
| Z103 |
2.5 mm |
Customer Reviews
Nice telescope. Great build, all parts are quality, Light and very portable. Takes great pictures. Looking forward to using this scope for a very long time
I bought the Z81 with the Dura Bright 2" diagonal (into which I put a 1.25" Baader 8-24 Hyperion zoom eyepiece) and later, Flat6Aiii, L-Pro filter and EOS-R adaptor.
It's early days and there have been a few good nights in Bortle 6 skies. So far, really happy and I can only see it getting better. Jupiter is crisp and bands are clearly visible; Saturn is crisp and gorgeous, as is the moon.
Tried M8(Lagoon)/M20(Trifid) with DSLR and L-Pro filter. For a first attempt at AP, was super pleased with the result (see uncropped image).
