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William Optics ZS110

Posted by Kurt Friedrich   06/09/2006 05:45AM

William Optics ZS110
My primary interest in telescopes is DSLR astrophotography. While I love to look through a 2nd telescope while I am doing exposures, capturing galaxies and nebula is my primary passion. For this reasons, I prefer refractors. I have had a several high quality refractors over the last 20 years, including
* 101mm f/5.5 TV Renaissance bought used in 1987
* 6" f/8.55 AstroPhysics Starfire bought new in 1989
* 100mm f/5 1990 TV Genesis bought used in 2003
*130mm F/8 1992 AstroPhysics Starfire EDT bought used in 2003
*80mm f/6 William Optics Megrez Triplet Fluorite bought new in 2004

My AP130 on the Tak EM-200 is a perfect set up at my house, but because of light pollution where I live, I wanted a scope that I can more easily transport in my car to a dark site. I already have a Losmandy GM-8, so when William Optics announced their new ZS110 at such a great price, I ordered one immediately. The GM-8 and the ZS110 are both a perfect size. 110mm makes for a serious camera lens, but still very easy to transport and setup.



Removing the new scope from the nice solid aluminum carrying case revealed a mechanical beauty. With its black anodized finish with gold trim, and that big STM coated objective, this scope will impress any astro on non-astro person. I also own WO’s ZS80, when I sit in my den chair with these black beauties on either side of me, I feel like I am in some kind of art museum.



I can’t think of a thing I would change on this scope. The graduated scale on the drawtube really helps get the balance right before it is dark. The focuser has a locking screw which is important when you use a heavy DSLR, and the rotating feature is nice too. The 10 to 1 focuser is so useful; it makes you wonder how we lived without them before. These focusers have 2 adjustments, an allen head screw, and a thumbwheel that rides on the same threads. There seems to be some art to getting the correct tension on each of these such that the focuser moves smoothly, easily, but yet will hold its position with a heavy load. I have read where some people have had a problem, but I have not had a problem on the 3 WO scopes that I owned. I also ordered the WO 114mm mounting rings, which are of the same high mechanical quality as the scope.

The ZS110 has lots of “in-travel”, which is allows it to work nicely with the William Optics bino viewers that I have. To get to focus visually, even with the WO 2” Dielectric Diagonal, requires the use of a 2” extension, which mine came with. For prime focus photography, it is also needed. I have used my TV 4x Powermate, and using the “eyepiece” configuration (rather than the Powermate’s T-ring adapter) it required two 2” extensions, and I had to cheat, and not put all the extensions fully seated. I have ordered a 3” extender so I won’t have to use that marginal configuration again.

Here are the specs from William Optics Web Site
• AIR-SPACED, TMB designed 110mm F/7
• STM coatings (from a private WO mail, with "best Ohara ED" glass)
• FMC on all surfaces
• 360 deg. rotating 2.5" Crayford focuser with 1:10 dual speed
• Adjustable tension and drawtube locking screw
• Graduated scale
• Aluminum tube, retractable dew shield, anodized focuser
• Golden trim finish and dew shield cap.
• High-precision CNC machined lens cell
• Laser engraved logo and specifications on the lens cell
• 1.25" adapter included with brass anti-marring compression ring
• Aluminum case
• 2-year warranty from WO
• Tube Diameter 4.5"(114 mm)

But of course, the most important thing about a telescope is the optics. I examined my lens, and it is perfect. No bubbles, scratches, or coating imperfections. Even though I also own an AP130 f/8, I was still pleasantly shocked at how big the 110mm lens appeared.



I think f/7 is an ideal focal ratio. Long enough that with a little help from a 4x Powermate they can do planets and globular clusters at 3080 mm, fast enough at f/7 to capture photons quickly, and with a flattener, it is even faster at f/5.6 and it covers a good chunk of the sky at 616mm. I have been told that TMB designed a new flattener specifically for this lens, and that William Optics has it in production now. I hope to get one soon.

First Light
First up was Jupiter. With my 5mm AP SPL I was at 154X. The scope is capable of much more power, but that night the atmosphere was not, and besides, I didn’t want to throw a barlow into the mix. I trust the color purity of the AP eyepiece, but not my barlow. I went for Jupiter as it is the brightest thing out there, and I am happy to say, there was not the slightest bit of false color. The bands on Jupiter were extremely clear, but at 154x, the air was visibly “boiling”, so higher powers will have to wait for another night. Although the Seattle area is almost always under the jet stream, so it might be a while. Arcturus was quite high in the sky, so I thought it would give me the best chance of a star test. The air was too turbulent for a good test, On the inside of focus, I could see nice perfectly concentric circles. On the out side I didn’t have enough travel to get to a real pattern. The star color was again perfect, no false color, and the orange was nice. Next I went to M13, which looked great. I then took out the extender tube, and put in my WO binoviewers with their supplied 20mm eyepieces and the screw in barlow. M13 and Jupiter were both spectacular.

Photography
I am really interested in galaxies and nebula, but to test the scope, my first night I shoot other things. Here is a shot of Vega. It is a min-max excluded average of 6 shots at 1/30th, ISO1600. Fairly boring picture, but the point is, no purple! (It was at about 45 degrees, so there is a touch of atmospheric distortion.)



Here is an attempt at a star test thru bad air. This is Arcturus, out of focus on the “in” side. A proper star test should be done with a single color at a time, but this image gives some idea of how good the lens is.



Lastly, I shot twenty-five 30 second exposures of M13. I can’t include the full size image here, but I was surprised how flat the field is.

On another night, I got a picture of the moon using Canon 10d. Here is a crop of one corner of that picture. Note how color free the edge of the moon is.




Here is a crop of another shot taken with the 4x Powermate. The seeing was not good enough for a perfect picture, but it shows me how good the scope will be if I get a still night.



Summary
Williams Optics is offering us a wonderful scope. I think it fills a very big hole between the many scope choices in the affordable 80-100mm range, and the “oh my god” price of the 130+ triplet refractors. In addition, it sits nicely on a reasonably priced mount (my GM-8). So for about $3500 you can get a very serious telescope. Maybe not as much resolution as 130mm triplet, but also not $8000+ for a 130 and suitable mount, and considerably more transportable. I can’t wait to put it to use for my main interest; driving to a dark site and getting about 20 eight minute exposures of some DSO that I can’t get locally.