William Optics ZenithStar 61II Doublet Refracting Telescope Review by Zane Landers
The William Optics ZenithStar 61 is a great starter telescope for deep-sky astrophotography and offers good value for the price.
The William Optics ZenithStar 61 is one of many 60-62mm ED doublet refractors offered as a beginner astrophotography telescope. It’s perfect if you want a simple, easy-to-use setup with similar mounting requirements and focal length to a telephoto lens but with the advantage of purpose-built optics and mechanics for astronomy. It delivers better value for the price compared to some of its near-identical copycats on account of some of the default mounting rail options which are provided. Like most refractor astrographs, the Z61 does not include a mount, eyepieces, camera adapter or other accessories, which you must purchase separately a la carte and will probably cost more than the telescope itself.
61mm (2.4) Aperture
360mm Focal Length
The William Optics Z61 is a 61mm (2.4”) f/5.9 refractor with a 360mm focal length. This is the same as many other 60mm f/6 refractors sold by companies such as Apertura and Astro-Tech; William Optics rounds up or simply doesn’t stop down the outer edges of the lens as much so that they can claim an aperture advantage over competitors. In the field, the actual performance difference is nonexistent. The Z61 is an ED doublet refractor with an FPL-53 ED lens element, reducing chromatic aberration to similar levels of that of a 60mm f/15 or so achromat – not gone, but minimal in images.
The Z61 illuminates a 35mm image circle which is enough for a full-frame or APS-C DSLR camera as well as most monochrome and color astronomy cameras. The field of view is not flattened by default, however, and you will need to pick up a field flattener. A 0.8x reducer-flattener would also bring the scope down to f/4.8 and 288mm focal length, beating out telescopes like the Radian Raptor in speed at the disadvantage of an extremely small image scale.
At 360mm focal length, you don’t need to worry much about autoguiding with most mounts, and image scale with most cameras is extremely forgiving of slight focus issues or poor seeing.
The Z61 uses a 2” rack-and-pinion focuser to hold your eyepieces or camera. The focuser has a 10:1 dual-speed reduction knob for fine focus adjustment, and plenty of travel and back focus to work with most imaging setups.
The Z61 uses a proper Vixen-style dovetail bar that extends the length of the optical tube rather than the too-short “foot” design supplied with many of its competitors. The dovetail is also compatible with Arca Swiss plates if you need that option.
The top of the Z61 has a handle attached which also doubles as a finder/guide scope saddle, fitting standard Synta-style guide scope rails and shoes. By having the guide scope directly atop the main telescope, you reduce off-axis torque on your mount and thus the mount is more likely to balance correctly and track/guide accurately. Most other imaging scopes have side-mounted finder/guide scope brackets and require expensive adapter hardware to achieve what the Z61 has by default. The handle also work as a Vixen-style dovetail so you can use larger, clamping guide scope rings or other brackets/accessories on top of it if you need to.
The Z61 only weighs 3.2 lbs (1.45 kg), so with a field flattener and DSLR camera you’re still within the weight limits of a mount like the Sky-Watcher Star Adventurer GTi, Explore Scientific iExos 100 or iOptron SkyGuider Pro. A bigger mount like the Sky-Watcher HEQ5 will give you more room to grow, however.
What can you see if you look through it?
The Z61 isn’t the best telescope for visual astronomy – it’s not really designed for it, after all – but will work nicely with eyepieces and a 1.25” or 2” star diagonal. With a 2” diagonal and wide-field eyepieces you can take advantage of the Z61’s short focal length for huge vistas of open star clusters and the Milky Way. Planetary detail is possible with short focal length eyepieces or a Barlow lens. Expect to see the phases of Mercury and Venus, craters and mountains on the Moon, ice caps on Mars, the rings of Saturn, and the moons and cloud belts of Jupiter. Uranus and Neptune are dots, and you can see a handful of globular clusters and galaxies, but none are of much excitement with aperture this small. With light-polluted skies, you will struggle to see any deep-sky objects at all with the Z61 apart from the brightest open clusters.
Due to its short focal length, you’re of course limited to large objects for imaging with the ZenithStar 61. Having to shop for a flattener and figure out focus/spacing yourself is also a bit of a drag.
Compared to a triplet refractor, the Z61 is not as well corrected for chromatic aberration, however this is hardly a worry with such a short focal length telescope.
The William Optics ZenithStar 61 is a great choice for beginner astrophotographers with a well-designed set of features and specs which make it easy to use without dealing with a massive mount and guiding. Compared to competitors, it delivers excellent value for the price too.