For expert technical support call:  +44 (0) 1392 791 001  or email: Powered by First Light Optics +44 (0) 1392 791 001
William Optics Zenithstar 103 APO
 William Optics Zenithstar 103 APOWilliam Optics Zenithstar 103 APO 

William Optics Zenithstar 103 APO

  (1 Review)
✓ 2 year warranty


Usually shipped 15-20 working days.

About this product

Model:  wo_zs103_gd
Part Number:  A-Z103II-GD

Latest model includes new CNC-machined handle/bar that enables you to slide a William Optics Uniguider directly into the handle (no need for Guide-Rings). 

The William Optics Zenithstar 103 APO features an air-spaced doublet lens with an Ohara FPL-53 ED glass element and fully multi-coated optics for high resolution, high contrast images virtually free of false-colour. 

Despite it's large 103mm objective diameter it is surprisingly compact and very solid! Many airlines will accept it as carry-on luggage. An ideal size for serious observations of deep sky objects and planets.

Versatile f/6.9 native focal ratio or f/5.5 when used with matching 0.8x flattener / reducer.

CNC machined aluminium for a superior fit and finish. 

Heavy duty, dual speed 2.5" 1:10 R&P focuser. A popular choice for imaging.

Available in Blue, Red or Gold anodised.  

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.


  • 103mm f/6.9 Doublet air-spaced APO
  • CNC machined ultra-high precision lens cell
  • FPL-53 ED glass element for enhanced colour correction
  • 2.5" Heavy Duty, dual-speed rack & pinion focuser
  • 0.8x Reducer / Flattener available separately
  • Innovative Bahtinov mask cover included!
  • Supplied with mounting rings, CNC-machined handle/bar, Vixen-style dovetail bar and Bahtinov mask cover

Telescope Field of View Simulator

What's in the box

  • Telescope OTA
  • Mounting Rings
  • Carry Handle
  • Vixen-Style Dovetail
  • Bahtinov Mask Cover


Aperture 103 mm
Focal Ratio F/6.9
Focal Length 710 mm
Objective Type ED Doublet, Air Spaced,
Fully Multi-Coated, SMC coating.
Lens Shade Retractable
Tube Weight 9.6lbs. (4.36 kg) - Including dovetail & Handle

Customer reviews

Average Rating (1 Review):  
Write a Review and share your opinions!

Rating (max 5):  
WO Zenithstar 103
Monday, 22 July 2019  | 

Scope arrived last week. I have only had a few days to play with it and very little time under the stars. It is a beautiful looking instrument and feels very solid. Nice smooth focuser and dew shield. I managed to get a quick look at the Moon and Jupiter. The Moon shows no obvious CA in the center of the FOV but does show some CA toward the edge of the FOV. Jupiter showed noticeable CA but it is very low down, the seeing was poor and the scope had not cooled down. The planet itself was quite sharp with detail though. A bit more CA than I had hoped for but it seems well controlled. Stars are tack sharp across most of the FOV. Looking forward to testing it fully when the nights get a bit longer.
The scope rests on my Skywatcher AZ4 mount with no difficulties and is easily transported outside fully assembled. It makes a great addition to my 127mm Mak as a grab and go instrument.


Please fill in the form below to ask a question.