William Optics ZenithStar 103 APO 2018

Review by Tim Cowell.


Can one telescope 'do it all'?

I can remember my first telescope for every wrong reason. A bitter experience having bought blind in the second hand auction market. I was excited during the 400 mile round trip to meet the seller, who was keen to show me his new telescope and not the pile of parts he had sold me. Back home I found the mirror to be home made and flawed, the secondary parts were broken and the focuser fell out. You won't be in any doubt that the William Optics Zenithstar 103 APO is a good telescope, in fact, it is a great telescope and a worthy contender for the best 4" / 100mm class, real-world, affordable instrument available and here is why.

The Sum of the Parts

The ZS103 sits towards the larger end of the current Zenithstar range. Sizings from 61mm to 71mm at the wide-field end to the 126mm option at the farther end all utilise the same basic design - an apochromatic doublet objective, employing FPL53 glass, in a stiff aluminium tube assembly, fitted with high quality accessories. These include a 2.5" shiftless focuser with fine control, the colour coded dovetail, tube rings and a carry handle, guide scope rings and the patented diffraction spike focus aid built into the lens cap. With these additional included parts the value proposition here is increasingly delightful. One must note here that there are are no tructural plastic parts and the assembly is very stiff, with the metal dew shield being suitably long enough to do its job properly.

The William Optics Experience

From your unboxing, through preparation and mounting, you will find yourself repeating the same word, over and over, the word quality. The ZS103's thick white coating is long lasting and not prone to fade or yellowing and forms a pristine and unblemished backdrop to the gold, blue or red colour coded parts which comprise - the lens cap and dew shield, the dovertail, carry handle and 'rings' and the focuser section. The completed

OTA is not very heavy and should not present a problem on suitable '5' class mounts in its 'all up' configuration. When mounted on our '6' it makes a solid platform for visual or astrophotographic duties .

Wintery Wonderland

With clouds gathering and the temperature dropping , William Optic's ZS103 was quickly mounted via its vixen type dovetail. Settling the telescope a little further forward in the strong and solid rings was easily accomplished by way of good sized knurled knobs. The 'rings' are softly lined in a similar fabric material to the lining inside the lens cap; a very welcome detail that prevents marking the contacting surfaces. With the dew shield slid fully forward, correct balance was aided. The imaging payload consisted of a ZWO ASI1600 mmc and ZWO 7 position filter wheel .Focus was found perfectly with the solid rack and pinion assembly 3/4 of the way out, where no sign of slop or wobble could be felt.

Connection to the telescope itself is made by a 3 screw assembly with an anti marring ring which gripped tightly. Other options include a screw threaded manual camera rotator with an engraved scale which would seem to be an untested but effective choice for imagers. There is also a properly designed focal reducer / field flattener which provides a 0.8 reduction and is fine tunable. This chnages the effective focal length from 710 and 568 and drops the focal ratio from native 6.9 to a usefully fast 5.5.

The Cold Light of Day

Having had a very successful first light examining the star field and reach of this beautiful instrument in standard F6.9 mode, the crisp and detailed previews elicited the sort of knowing nod an old hand with an heirloom 'scope might make. However in this case the outlay is likely a good deal less than you would expect and I think that a 'high street' type manufacturer will be shocked to find their seemingly similar offering is currently several hundreds pounds more and might lack - FPL53 glass, quality assurance and factory testing, generous standard equipment and included accessories. William Optics offer first class product support with their 24mth warranty, though you feel you will not need that, and in a digital age they can be contacted not only by telephone and email but also through social media, including Facebook messenger.


Aspirations and Accolades

“In a relatively short time, William Optics has established itself and its products as one of the world leaders in short-tube, highly-portable refractors, and has achieved quality recognition for many accessories such as the well celebrated WO Diagonals. ” Not bad for a telescope designer who began with his grandma's glasses lens, a roll of newspaper and the eyepiece from a broken microscope. In 2007 William Optics joined in a venture with Ferrari, the world-renowned supercar manufacturer. WO and Ferrari collaborated to invent a fashionable, carbon fibre, light weight refractor, for telephoto lenses known as the ZenithStar 70 F430.

This joint venture also led to the F1 binoculars. William Yang says this about his company, “Our philosophy of 'More quality for Less money' is aimed at making instruments outside the reach of the average pocket, such as apochromatic refractors, affordable.


Finders Keepers

It is hard to conclude a review where you have found yourself enjoying touching and looking at a piece of kit such as this 'WO' ZS103 as much as we have during this week. In fact, I find myself now looking at 'it' warming back up from a brisk and chilly Somerset night, where the in built coarse focus temperature guage measured a cool -2 C (useful for my session log). The price versus quality ratio has, for once, slewed firmly towards affordable, with absolutely no compromise on build. You will be unlikely to need an upgraded focus unit, nor mount fittings, or guide rings, which leaves you healthily in pocket. The pride of ownership factor is certainly there - this is a telescope your friends and club will drool near. It is a grown up 'scope with the looks of a classical refractor, swathed in class and embellished tastefully. Is it a keeper? I bought and paid for this one from the first batch and was not surprised that it quickly became a best seller. Your only real decision is which colour would you like, red, blue or gold?