William Optics Zenithstar 73 II APO 2019
 William Optics Zenithstar 73 II APO 2019William Optics Zenithstar 73 II APO 2019 

William Optics Zenithstar 73 II APO 2019

  (3 Reviews)
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About this product

Model:  wo_zs73_gd
Part Number:  A-Z73IIGD

New 2019 model

The NEW William Optics 2019 Zenithstar 73 APO features an air-spaced doublet lens with fully multi-coated optics and an Ohara FPL-53 ED glass element for sharp, high contrast images virtually free of false-colour. 

Provides high resolution images when used for astrophotography or wildlife photography and is a convenient ultra-portable telescope for visual astronomy (think binocular astronomy targets).  

It's fast f/5.9 focal ratio and compact size makes it ideal for convenient wide field astrophotography or piggybacking. 

CNC machined aluminium for a superior fit and finish. 

Dual speed 2.5" 1:10 R&P focuser.

Available in Blue, Red or Gold anodised.  

Supplied with mounting rings, Vixen-style dovetail bar and soft case. 

Ohara FPL-53 vs FPL-51 ED Glass

The dispersion properties of ED and SD glass elements are important in determining the overall colour correction. The abbe index is used to quantify the 'partial dispersion' of a particular glass. Pure Fluorite offers the highest partial dispersion at around 94.99 V, Ohara FPL-53 glass is very close to Fluorite at 94.93 V and is often referred to as Synthetic Fluorite.  FPL-53 is also noticeably better than Ohara's lower spec' FPL-51 glass which offers an abbe index of 81.54 V.

Field of View Simulator

What's in the box

  • Telescope OTA
  • Innovative Bahtinov Mask
  • Mounting Rings
  • Vixen-Style Dovetail
  • Soft Case


Aperture73 mm
Focal RatioF/5.9
Focal Length430 mm
Imaging Circle43 mm
Objective TypeED Doublet, Air Spaced,
Fully Multi-Coated, SMC coating.
Lens ShadeRetractable
Tube Diameter93mm (3.66")
Tube Length390 mm Fully Retracted
Tube Weight2.83 kg

Customer reviews

Average Rating (3 Reviews):  
Write a Review and share your opinions!

Rating (max 5):  
Great scope with some points of attention
Tuesday, 14 July 2020  | 

Nice scope to work with. Though there are a few minor points I encountered. The fancy temperature gauge is off by 3 degrees celcius (why?!). When using a dslr, no declination balance can be achieved, because de dovetail cannot move further back because of the focuslock screw (need a secondary dovetailbar or spacerblocks for the scoperings). I added metal washers to the dovetail bolts, since the bolts left impressions in the metal (no overtightening). I like the built-in bahtinov mask. The focuser is precise and smooth, love it! The gold colour tends to be more towards orange (compared to the photos and older WilliamOptics). The WO73flattner I ordered together has a matching colour. Last point since the flattener is screwed into the scope, changing to visual you need to unscrew the flattener, re-attach the original scope part, then you can connect the WO dielectric diagonal, and then you can use your eyepieces. A slide in 2 flattener is easier. I am happy with the scope, despite these points mentioned (okay, the temperature gauge is disappointing)

Rating (max 5):  
Monday, 11 November 2019  | 

First one received was faulty but FLO were great and shipped the replacement before I had even returned the faulty one.

Build quality is superb, this replaced and ED72 and things like the focuser are in a different league. Used in combination with the ZS73 flattener the field is perfect from corner to corner.

Rating (max 5):  
Monday, 24 June 2019  | 

I purchased this from FLO earlier this year to go with my Star Adventurer mount (also FLO) and a Manfrotto photo tripod. Initially I thought it was going to be too heavy especially with a Nikon DSLR (APS) mounted but the mount chugged along nicely. The optics on the ZS 73 APO are really nice just managing to the corners on my D5100 but falling off with the FX chipped 800E. I then purchased it's Flat 73A adjustable flattener (not FLO) and the difference in field flatness was very marked even with the FX sensor. The flattener is x1 so no changes in FoV to contend with. I have been taking mono photos with the D5100 up to about 3 mins which is about the best I can get from the Star Adventurer. It's a great visual scope too. Paired with my ES 68 and 82 eyepieces the views are better than I ever expected. I took the ZS-73 up to the Lake District under some better skies than I usually deal with - what a treat.


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