05/01/2019

The William Optics Zenithstar Doublet Refractor is truly a work of art. Small in size and powerful in practice makes this portable refractor a mainstay in my lens collection. A focal length of 360mm at F5.9 allows this scope to rival some of the larger refractors on the market. The portability alone is worth the price. I was turned on to this particular beauty by Trevor from Astrobackyard

While the price tag looks extremely eye catching ($399 US as of this article) you need to be conscious of what accessories you cannot live without.

The “recommended” field flattener is less of a recommendation rather a must have. I tested this without the flattner installed and there was severe curvature from the corners of the picture towards the center. If you’re only planning on using a 1/3 of the scopes viewing power to shoot the night sky that might not affect you but I am willing to bet you aren’t buying a refractor for just the inner center imaging capabilities. The field flattener is a necessity for any serious astrophotographer and will correct the image to gain round, crisp stars all the way to the edge. The field flattener is priced at $198 US as of this articles date. Combine the two and your $399 price just ballooned to $600 US before taxes and shipping depending where you purchase it. No small chunk of change but still reasonably affordably compared to the thousands you could spend for similar functionality. One thing that took a while to figure out was how to add a filter inside the flattener. There is minimal information available from William Optics on this topic but searching a few well known astrophotography sites such as cloudynightsgave me the answer. On the back half of the flattener is a spacer to set the length required by your camera for optimal focus. If you unscrew the space ring and then unscrew the back cap it will open up. There are internal threads on the back half of the spacer that will accept 2 inch filters. Replace the parts and the filter is installed. For those that would prefer using multiple filters throughout the night I would suggest looking in to a filter wheel. There is a bit of force required to loosen the rings which can throw off your focus spacing if not reset correctly in the dark. An alternative to this is to conduct your specific filter sessions separately on different nights. It’s not the quickest way to get your perfect photo but if this hobby teaches you anything it’s patience.

The first thing you notice on the WOZ61 is the eye popping color scheme you chose. The gold really stands out and comes in Blue and Red versions as well. While this is not a deal maker in choosing a scope it certainly feels nice on the eyes. The dew shield retracts and extends based on your needs allowing this scope to easily fit inside of my camera bag on longer excursions especially at 3.19 pounds of weight. Add in the field flattener and you’re still under 4 pounds (+0.59lbs).

Looking down the barrel you immediately notice the fine quality of the Synthetic Flurorite glass that is perfect for wide field astrophotography at 61mm. You will find sharp consistent edges even doing landscape or nature photography.

Newer releases of the Z61 come included with a built in Bhatinov mask for precision focusing. The mask is hiding under the lens cap and can be revealed by twisting off an additional metal cap. I have had several masks that were either lost in the middle of a session or broke because of cheap quality. Having something like this built in to the lens cap is a perfect solution. William Optics does sell replacement caps if you lose one but they are not cheap. For the 61 series they start at $78 US and go up from there depending on your size and model.

The focus knob is smooth with very little effort required to make minor adjustments.

The Z61 comes with a focus knob thermometer to help identify temperature changes that would indicate the need to refocus. I have yet to use this feature as it’s intended partly because it’s not something I’m used to and it’s hard to tell what the needle is reading unless you shine a light on it in the dark. I can attest that it at least works as it dropped rapidly in the -20F polar vortex this past winter. Probably should have waited to use it under those conditions but clear nights are a rarity in a midwest winter. At the very least it’s a nice analog aesthetic in a very digital hobby.

As luck would have it mine arrived on a crystal clear winter night but a full moon. Not having a proper EQ mount at the time I wasn’t about to try and get deep space nebula’s on a standard tripod with full moon glare. To top it off the Chicago weather was -20F overnight and windchills were even worse. The only proper test shot I’ve had with the Doublet was this 99% full moon. Given the conditions I was pleasantly surprised at how crisp the raw’s came out and the ease to process them. I have a Sigma 150-600mm contemporary lens that is probably one of the sharper long lenses on the market. The Z61 tops it by far in details captured. I thought about adding my 2x extender but decided against it this go around. The extender would allow me some additional magnification but would not be a true test of the base glass package or sharpness of the refractor as they are not the same quality.

Final thoughts, The William Optics Zenithstar 61 APO is definitely a worth while investment. Affordable portability combined with razor sharp details allow you to go almost anywhere with this refractor. Whether it’s on a portable tracking mount such as the Skytracker Star Adventurer or a standard EQ mount with RA and DEC drives you will be hard pressed to over load the motors on either. These refractors are becoming hard to find and frequently backordered. If you’re on the fence it’s affordable enough to not make a major dent to your finances but will retain it’s value for years to come.