William Optics ZS66SD *updated 15th feb*

[iancandler]

William optics ZS66 SD APO

Please note I have no affiliation to William optics or their suppliers.

The William Optics ZS66 SD APO is another in William Optics long line of small portable high quality refractors.

Specifications:

66mm SD Doublet, Air Spaced, Fully Multi-Coated, STM Coatings

388mm focal length

F5.9 focal ratio

1.6" (40.6mm) Crayford Focuser, 1:10 Fine Focus

63mm (2.5") Focuser Travel Length

Rotatable Focuser Design

Retractable dew shield

Resolving power 1.78”

Limiting magnitude 10.8

On opening the box I found the aluminium hardcase that contains the scope, this is substantial and should protect the instrument well both in general use and even when taken on airline flights.

The inside of the case is filled with a well-cut fitted foam insert that not only cushions the scope but also provides extra storage for other accessories.

The scope itself is up to William optics usually high standard, sporting a nicely powder coated CNC alloy tube assembly and the usual crayford rotatable focuser with 1:10 fine focus.

It does however differ from the 80mm WO scopes in that the focuser drawtube terminates with a screw-on cap that provides a 1.25” fitting for diagonals and not the usual 2” with a reducer.

Unscrewing this cap reveals a set of SCT threads that can be used to connect larger 2” diagonals and various accessories. (We will come back to this later).

There is still the provision to mount a WO finder on the tube and the L bracket that allows standard tripod mounting has been updated so that it will now also fit into most vixen style dove tail clamps.

The whole scope lives up to the benchmarks we have come to expect from William Optics, the lens assembly and coatings look even and flawless, the tube is almost a work of art and the focuser smooth yet positive.

There seems to have been a lot of confusion over attaching diagonals and accessories to this little scope so hopefully I can clear some of that up before we go any further.

As standard the scope doesn’t take 2” push fit diagonals and accessories, to add them you will need to use an SCT thread to 2” push fit adaptor or if you own a WO or clone diagonal purchase an SCT fit nosepiece that can replace the push fit one on your diagonal. (Just unscrew the push fit one from your diagonals body and screw in the SCT one to replace it)

Some push fit diagonals wont come to focus with this scope when used with certain eyepieces. (I know some have had problems with Hyperions)

Where possible its best to stick to WO diagonals or their clones such as those from smart astronomy etc.

I have used mine with both a smart astronomy WO 2” clone fitted with the WO SCT nose piece and with the WO 1.25” push fit carbon dielectric diagonals without having a coming to focus issue on the following eyepieces:

Celestron 2” and 1.25” eyepieces (plossls)

Antares W70’s

Burgess/TMB planetary’s

Televue Panoptics

Televue Radians

Antares plossls

Meade Plossls

Moonfish UWA

Japanese Ortho’s

Bausch & Lomb plossls

Standard cheap 2x 1.25” achromatic barlows

GSO 2x 2” ED Barlow

I have also not had any problems using filters except SCT fit ones (not enough forward focus travel to compensate for the width of the filter housing).

Focal reducers can be a problem due to the limited travel as outlined above.

My Antares F6.3 SCT focal reducer was to wide and I couldn’t get enough forward focus travel, but the WO 0.8 x focal reducer/field flattener works perfectly for imaging use. (More on this item later)

In use

My main reason for buying the scope was that I needed a lightweight refractor I could use as a grab & go scope as well as for imaging with a DSLR camera.

This little beauty hasn’t disappointed in either respect.

It’s so light and portable that even on a bad day I can easily carry it.

Mounted on my camera tripod it gives me a very light weight grab and go scope that I can use not only for astronomy but also bird and wildlife watching.

Fitted to my little Merlin mount for visual astronomy and lunar imaging it’s perfect for me, and mounted on my CG5 excellent for long exposure astro imaging.

The first object I viewed was the moon, and a nearly full moon at that, here it surprised me with its level of colour correction, as it was hard to detect any false colour on the limb at all.

Contrast was excellent as well and it soon had me pushing the magnification up too, and past that recommended.

I spent some time looking at the detail contained in Mare Crisium and the adjacent crater Cleomedes, finally trying a 6mm Burgess/TMB and a 2x Barlow to give approx 133x magnification, the scope handled it with ease and gave me some of the most rewarding views I have had of the lunar surface.

It was then time to turn to M45 and M42.

The Pleiades was fantastic, especially using the 19mm panoptic I had just purchased.

Even with my level of light pollution and a bright moon I was still blown away by the view.

M42 had me at the eyepiece for over an hour.

I started with the 19mm panoptic and then just kept switching eyepieces and adding or subtracting a Lumicon deep sky filter until I finally ended up with a 9mm Burgess/TMB and the Lumicon deep sky.

The level of detail I could see was fantastic! It just leapt out of the eyepiece at me.

At one point I just sat at the eyepiece for a good 20 mins and as the time passed so more and more feint nebulosity became apparent.

Of course I had to give it a good test on colour correction so the next day aimed for Sirius.

No problems at all, a crisp and clear view.

For visual use this scopes diminutive size is misleading, I have bemused those around me by leaving the SCT indoors more often and instead finding myself sitting outside at the ZS66. Having said that once they have a look through it they understand why.

Imaging.

I wont pretend to be anything other than a novice imager, for I am not, my experience to date consists of wide field images taken with my DSLR and a lens and a few Lunar shots taken with the ZS.

The problems with the limited forward focus travel really do make using as short as possible a connection between the camera and the scope essential.

I struggled at first as all my previous equipment had been geared towards 2” push fit but all that was cured by firstly purchasing a Male T thread to female SCT adaptor for my camera.

This in itself can be connected directly to the SCT thread on the focuser tube and gives a good image.

I also decided to bite the bullet and purchase the WO 0.8x focal reducer/field flattener for the scope.

Now this has an added benefit as it terminates in a Male T thread at the camera end that allows you to screw the camera’s T ring directly to it.

This seems to place the reducer perfectly for my DSLR. (Please note this reducer is designed for photographic use not visual)

The Reducer connects to the focuser tube via an SCT thread, but also comes with a 2” push fit adaptor so you can use it on other scopes as well, it also has the facility to allow you to rotate the camera for composition.

I wish I could say that I have done a lot of deep sky imaging with it but haven’t had the opportunity yet though from the images I have seen from others its defiantly not going to disappoint and it certainly makes connecting a camera easy.

In conclusion.

The ZS66 is really a scope that everyone should have in their armoury at some point.

Its just so useful, in fact its versatility is fast becoming legendary with many also using it as a guide scope for a larger imaging set up, others like myself using it for both imaging and viewing.

You can literally be outside and using it in seconds if you wish, and its portability means it can be taken anywhere in the world quite easily.

Overall I wouldn’t be without this little scope its just so enjoyable to look through and easy to handle.

No longer do I have to worry about having a good day in order to use my scope, in fact I have even used it from indoors on a really bad day and still had rewarding views

I can honestly say that even if I won the lottery tomorrow I still wouldn’t get rid of this scope.

*update 15 th Feb*

There had been much confusion when I spoke about trying binoviewers with this particular scope and after having purchased a pair of BO ones second hand I can now firm up a few things.

The scope will work with a binoviewer but you will need an OCA for the binoveiwers.

Luckily mine came with both the BO OCA and a pair of 20mm BO binomate eyepieces.

The binoveiwer will not however work in a 2" diagonal with the 1.25" adaptor, there just isnt enough "in" focus travel to allow for the larger size/longer light path of the 2" diagonal, even when the diagonal is fitted via the SCT threads.

If you only have a 2" diagonal I would recommend getting a good quality 1.25" one such as the one from WO, just make sure the thumb screw is a large one that can be securely tightened. (The brass compression ring type are preferable)

In use the 20mm binomates and the dedicated OCA gave a lunar image that fills approx 2/3rds of the FOV .

The magnification of the one set of eyepieces can be varied by using different barlow elements , screwed lightly in place of the OCA.

Please note your barlow needs to have a removable nosepiece element to use it like this, also note the threads do not match up which is why I say lightly screw it into place, it only catches on the first couple of threads on mine but its enough to hold it in place. DO NOT FORCE IT

I have been using mine with the WO 1.25" carbon fibre diagonal, without issue.

For targets that are either terrestrial or low in the sky a 45 deg 1.25" diagonal can be used, I have an old meade one that works fine.

So far I have had no issues in merging the images but I have yet to try 9mm eyepieces which is my next objective.

As for the eyepiece list, you can also add the meade 5000 series SWA eyepieces as I have just obtained a 16mm that works perfectly.

I am still awaiting the arrival of a 2.5X APO barlow and will post results as soon as I have recived it and had a chance to use it.

[barkis]

That's a wonderful concise, and honest appraisal of the scope Ian. I am sure that a potential buyer will find this a great help in deciding

whether or not this little unit is for them. Of course the Name is synonymous with quality. I have a WO ZS66, just recently purchased, and I just keep looking and touching it. Can't do much else really, it has rained almost non stop since it was delivered.

Ron.

[Neon]

Another great review Ian, with loads of information. Nice one.

[FLO]

An interesting read Ian

[jgs001]

Ian, thanks, that's good read and a nice review of a very nice looking piece of kit.

[hairycrab]

Nice review Ian. I have one myself, barely 2 weeks old. I'm having fun using it for imaging with my Nexstar mount, the L-bracket allowing it to be used with dovetail or photo tripod.

[iancandler]

Bump for update

[assouptro]

Nice review

I have just purchased one of these baby's and am looking forward to trying it out

clear skies

bryan