ZenithStar 66mm ED APO

ZenithStar 66mm ED Triplet APO Refractor
by R.J. Waldman

Guess I'll start this out by saying I have no affiliation with William Optics or any other companies in this review. But you've likely read plenty of reviews, so you know how all that goes...

As an avid camper/hiker/traveler, I'm always on the lookout for a good travel scope that will go absolutely anywhere. For the past few years this position has been filled by a 70mm f/5 Orion achromat. Although it was a nice scope, it was still, well, an f/5 achromat. Whenever a brighter target caught my attention I had to put up with the bright purple halo. However, when William Optics released the ZenithStar 66 line of 66mm refractors, I just knew I had to have one. After careful research and negotiations I convinced the parental units that the ZenithStar 66 triplet apochromat was the ideal Christmas present. Then the waiting began..

The shock of ordering a new scope was just beginning to wear off, when suddenly I heard something that sent a chill down my spine and set my heart pounding...

A diesel engine idling outside my house...
Of course, there can be only one thing that makes this sound...

The FedEx truck

Before you can say APO, I'm in front of the front door waiting for the doorbell to ring. And it does. And there's the delivery guy, obscured behind an alarmingly large box.

I'm thinking Does a 66mm scope really need a box that big? Of course, there's only one proper way to find out. I need to open the box. One look inside tells me why the box is so large. The scope's shoebox-sized box is securely held in the outer box by a thick layer of packing peanuts. This makes a very secure package. It also made a mess in my kitchen. By this time I can hardly keep my hands steady as I remove the contents of the box.

So what exactly is in the box? The first thing that came out was the carrying case. It is black with the WO logo in red on the top, and a shoulder strap. Okay, that was the only thing in the box, but it's really all that counts. Or more accurately, it's the scope in the case that counts.

And what a scope it was

At first sight, this scope looks like a work of art.The scope is a 66mm ED (which stands for extra low dispersion", a.k.a "fancy ) apochromatic triplet with a 460mm of focal length. From the fit and finish to the slick black anodizing, everything about the outside suggests that what's behind that gold metal lens cap will be worth every penny. Still, I have to take the scope out and play with it a bit to be sure.

The scope is covered in slick black anodizing from the tip of the dewshield to the end of the focuser. It attracts fingerprints like some sort of crazy oil magnet, but WO threw in a small microfiber-type cloth to clean the tube. I rack the crayford focuser in and out. It is by far the smoothest focuser I have ever used. If it were any smoother, I could make it move by thinking about it. The focuser is a 1.6 focuser, threaded for SCT accessories. A 1 1/4 adapter is included. I release the rotating focuser lock and rotate the focuser. I expected it to be very sloppy when unlocked. It had hardly any slop, which, as I found out later was completely eliminated by a five minute tweak. I slid the retracting dew shield out. It slid out smoothly and stayed out without slipping.

The scope attaches to a mount via an L-bracket with cork grips and a pair of 1/4 -20 holes. A quick peek showed the well-coated triplet lens. Mechanically, this scope is the best I've ever used. And I've used some pretty nice scopes. By this time I was just itching for first light.

Darkness didn't come fast enough that day. First light was carried out with a standard Celestron 1.25 mirror diagonal and a light photo tripod, the only mount and diagonal I had that would work with the scope. The seeing and transparency were so-so at best.
My first target was Mars. The scope doesn't have a finder, but with only 460mm of focal length, I could achieve a very wide field of view. I located Mars with a 40mm Plossl, which gave 11.5x and a view almost four degrees across. Mars was a small, orange disk. Orange. Not purple. Or red, or blue, or any other unnatural color I'd associate with an achromat.

My first look through an APO was all I imagined it would be. There was some spiking visible, but that was entirely from my poor eyes. I bumped the power up to 92x, revealing a small orange disk with some detail visible. About what I expected for such a small scope.

My next target was the Pleaides: At 11.5x, the cluster was framed nicely. Pure blue-white stars, very sharp However, the rotating focuser was bugging me. It seemed to have loosened since earlier, constantly a bit loose even when I tightened the lock knob. Though at this point I still didn't know the truth of the problem. That's still later.

On to a quick star test. I chose to test on Capella. I saw round rings on both sides of focus. I thought there was a bit of astigmatism, but the fact that the orientation relative to focuser position changed every time I tried it confirmed it as a mild case of averted imagination. The seeing was bad enough that I couldn't see an Airy disk in focus, and out of focus, diffraction rings were hard to see. But it was still good. What I did manage to see was good, and no false color.

All too soon the clouds put an end to the session. Which would be my last until Christmas. This was a Christmas present, after all. Once I'd made sure everything was okay it was to go right back in the box and under the tree.

Before everything was packed up, I flipped on the light to diagnose the loose rotating focuser. It turns out I wasn't even using the rotating focuser In the dark I had unscrewed the focuser from the tube and I was rotating it at that point instead Tightening that down removed 90% of the slop. A close look finally found the source of the remaining 10%- one of the three small setscrews that hold the rotating focuser on had worked itself loose, and tightening it a bit made the focuser perfect. No slop, even when unlocked. And as for the actual focusing action, it was so nice I pretty much forgot I was focusing. No fiddling, no backlash, no raising the focuser past focus then easing it back down; I just tweaked the focuser and viewed. Though I did do an unusual amount of focusing, as the combination of heavy eyepiece, shaking mount, and overhead viewing made the focuser constantly slide unless I locked it. Some day I may adjust the tension, but only if the problem gets worse with large eyepieces.

All too soon it was over. The scope went back into its case, the case went back into the boxes, and the whole thing went under the tree until Christmas. It was going to be a lonnnng month...

Fast forward one month. I couldn't wait for Christmas. I just haaad to put the scope to the full moon CA challenge This time the scope rode on an EQ-3 equatorial mount, which was quite stable under such a small scope. At 18.4x, the moon was bright against an inky black background. There was just the tiniest trace of a blue rim. Higher powers showed similar results. However, when the moon was out of the FOV, a strange round, colorful ghost image, resembling a rainbow flared into view. Careful examination showed that this was coming from the anodized front end of the SCT-1.25 adapter. Once the moon was in view this disappeared.

I took advantage of the fine seeing and give a star test another shot, again on Capella. The rings were identical on both sides of focus. The scope showed some miscollimation, but I'm not sure how much of this came from the cheap Celestron diagonal I was using, and without an extension tube I couldn't check without a diagonal. I'm sure the oval nature of the miscollimated pattern is what I mistook for astigmatism on the first test. Even with this miscollimation, views were good. Castor was easy to split, and all four main stars in the Trapezium were visible, and the nebula was detailed even with the moonlight. Just for the sake of experimentation, I stuck on a Celestron 2 SCT diagonal. As has been mentioned elsewhere, the combination would not focus; the Celestron diagonal was about half an inch too long. Which, to me, is just another excuse to get a nice William Optics diagonal.

All minor issues aside, everything about this scope screams quality. Despite the tiny size, it feels like I got my money's worth.