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William Optics Zenithstar 73 III APO Refractor OTA

William Optics Zenithstar 73 III APO Refractor OTA
Price:  £549.00(Inc. 20% VAT)Earn 549 Loyalty Points

Model:  A-Z73IIGD
Brand:  William Optics

2 Year Warranty On All New Items
(Excluding Batteries & Globes)

  (1 Review)

Now complete with soft case as standard

2019 All New Zenithstar 73 APO

Zenithstar 73 is a greatly versatile and portable refractor telescope for beginners and veterans alike. Designed for both astrophotography and wildlife photography, high power visual observing through the Zenithstar 73 is also hugely satisfying. The image is crisp, sharp and colour aberration free thanks to the use of top quality glass — FPL53, closely matching the legendary fluorite material. The 43mm image circle when Flat73 is used covers full frame size sensor nicely.

An in house Zygo interferometer test & report is available with this telescope. Click here to read about the interferometer test in more detail. There are various packages available on this model. Please select from the packages above. The optical test and enhance includes a full inspection of the telescope, including optics, focuser, paintwork and other mechanical parts. A precise optical check is then performed then the scope is enhanced to ensure you get the best possible optical performance from your new instrument. 


The interferometer is essentially a measuring instrument. Within the interferometer is a calibrated laser that is pointed through the optical test surface, then onto a high quality reference sphere, then back through the test subject then to an internal camera which gives us the measurement on the screen. From this, we can adjust the position of the test optic and the reference sphere to obtain a perfectly calibrated system. The more central the laser to the test optic and then on return, the better and more accurate reading and measurement we can take. This takes a lot of adjustment to get the best results from the optical surface. Once the measurement has been taken, we are provided with a series of results that show the optical quality of the surface plus other information. We will aim to provide 0.95 Strehl or higher. 

ZenithStar 73 f=430mm
F/5.9 FPL53 doublet APO

Retracted Length:390mm
Weight :2.83kg
2.5” R&P Focuser

Package includes:

‧ Z73 APO

‧ Innovative Bahtinov Mask

‧ Mounting rings

‧ Vixen style Dovetail

‧ Soft Carry Case

Optional accessories:

‧ Guiding rings

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

Awesome Telescope
Sunday, 21 February 2021  | 

I bought the Z73 purely on the basis of Trevor Jonesís gushing reviews and I purchased it purely for Astrophotography purposes.

Having found a new passion for Astronomy only 2 years ago after a 20 year hiatus and discovering that you could actually image deep space objects from your own back yard was an opportunity I couldnít allow to pass me by.

I bought the scope as a package from RVO which included the Z73, 50mm guide scope, mounting rings, dove tail bar and integral bathinov mask. I also bought the Skywatcher HEQ5 Pro mount to get me off and running.

The telescope itself looks awesome (Iíve got the Red trim model) Itís rock solid, sleek, finished beautifully and is really well made.

Now onto the important bits -

- As a wide field telescope for astrophotography this scope is excellent. In my opinion, there isnít another telescope on the market that compares to the super sharp optics, quality of build and usability of this scope at what is a very reasonable price for what you get.

You will however 100% need the William Optics dedicated field flattener if you plan to use this scope for astrophotography.

I use the Z73 with the field flattener and a Canon 200d Astro modded DSLR camera which has a C-Size sensor mounted on the HEQ5 Pro mount and the results are simply astounding.

This telescope is a wide field scope and is absolutely perfect for imaging open star clusters (Pleiades) vast nebulae (Orion, North America, California) globular clusters and also certain galaxies (Andromeda, Triangulum, Pinwheel) to name just a few.

If you want to take images of distant galaxies then this isnít the scope for you. If you however want to image vast nebulae, star forming regions and their surrounding nebulosity then this is the scope for you.

I cannot say enough about this scope and even seasoned pros hold this telescope in high regard.

I would pigeon hole this telescope as an upper mid range piece of equipment. There are a lot more expensive scopes out there and there are a lot less expensive but as far as quality of optics and affordability is concerned, you will not find a better 430mm focal length - 73mm apochromatic refracting telescope on the market to come anywhere close.

Even the more expensive apochromatic triplets and quads that are available of similar focal length and aperture will not come close to the quality of this scope.

5 stars all the way. 10 out of 10. Simply put the best scope on the market in this focal length / aperture range.

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Rother Valley Optics


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Rother Valley Optics Ltd is registered in England and Wales 04762707. Registered Office: 21 Station Road, Kiveton Park, Rotherham, S26 6QP. Rother Valley Optics Ltd acts as a credit broker only. Rother Valley Optics Ltd are authorised and regulated by the Financial Conducts Authority. Credit provided subject to age and status..

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01909 774 369