My equipment review part 2 : William Optics Zenithstar 73 APO

© 2019 William Optics

I’ve dabbled in astro-photography over the years, with ok results. I figured as astronomy is a life long endevour, I might as well put the time and effort in getting the right tools for the right job. I’ve sat in the middle ground, so to speak, with Schmidt–Cassegrain telescopes (SCT), so decided to go for a full on refractor. I also wanted to have a good spread on focal lengths from a 2800mm (EDGE11 HD) to a 1500mm (Celestron NexStar Evolution 6″) and now this provides me with a 430mm focal length. This type of scope uses convex lenses to present the light as you see it in your eyepiece.

Here’s a rudementary drawing I made of the basic workings of a refractor telescope

The William Optics Zenithstar 73 is a beautifully designed wide field refractor designed and built for the astro-photographer but serves as a great visual tool also. It’s nice and fast at F/5.9 and with a focal length of 430mm it provides really nice wide field views. It’s got a dual speed 2.5″ rack and pinion focuser which is really smooth. Another cool feature of this offering is that it has a built in Bahtinov mask allowing for pin point accuracy in your focusing.

Bahtinov Mask embedded into the scope

© 2020

I use this with a light astrophotography camera, so weight is not an issue, however, I feel WO could have supplied an extension tube with this scope, seeing as its touted as an astrophotography tool. An extension tube is needed to achieve focus. Luckily, I had a spare one, but not everyone will have this or realise they need one until they are setting up and cannot achieve focus.

1.25″ Extension tube. © 2020

© 2020

Visual observation with this scope is pretty good. For example, below is an image of how you can expect to see M42 (Orion Nebula) with an 18mm 82° field of view eyepiece and a 30mm 82° field of view.

image credit: © 2020 First Light Optics.

I didn’t purchase an additional mount for the telescope. I have a CGEM mount in good working order, it’s just a case of swapping out the tubes. I had a spare Losmandy style dovetail plate for an 11″ SCT, all it needed was a slight modification by drilling and threading holes and ensuring they were in a line dead center, the Vixen-Style Dovetail bar supplied with the ZenithStar 73 could be fixed to it and held securely on the mount. I used allen bolts for this as they easily fit into the recess on the vixen style bar.

Below image shows the set up secured in the jaws of the mount.

© 2020

William Optics 50mm Guidescope with 1.25″ RotoLock mounted on the ZenithStar 73

© 2020

The scope will take either a DSLR type camera or a dedicated astro-photography camera. If using the former be sure to have a 48mm T Ring mount for your Canon or Nikon DSLR which you can buy from any good astronomy equipment vendor.

I haven’t really had too many opportunities to put this to the test regarding imaging. I did however download the ASICAP software for the ZWO camera and is available for both MAC OS and Windows. I’ve been getting to know this and early impressions are good, I find it’s not too complex and I got up and going fast enough, of course it’s easy when you have a target like the moon, but I’ve also tried it out on the Hercules Cluster.

© 2019
© 2019

Field flattening is taken care of by using the William Optics Adjustable Flat73A. I had to play around some to get the focus correct, but it’s not too difficult. There’s some great information on using the field flattener on this page.

All in all, this a very easy scope to use, lightweight and portable. There’s an optional padded case available for this that will take some accessories too. I hope you found some parts of my review somewhat useful.

Next up….Celestron EDGE 11 HD

2 thoughts on “My equipment review part 2 : William Optics Zenithstar 73 APO

  1. Nice review. The Zenithstar looks like a great scope.

    I am used to popping my Bahtinov mask on and off the front of the objective lens (and sometimes losing it in the dark), so you peeked my interest with your comment that a mask is built in. How is it built into the scope?


    Liked by 1 person

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