The Z100’s Newtonian Reflector and Focuser
The Z100 is a 100mm (3.93”) f/4 Newtonian reflector. At such a fast focal ratio, you’d expect there to be some coma, and you’d indeed be right. It’s not noticeable with the stock 17mm and 10mm eyepieces, but with a lower magnification eyepiece like a 25mm Plossl, you’ll start to spot it at the edges of the field of view.
Additionally, at f/4, precise collimation is critical for optimal performance with any reflector. Unfortunately, the folks at Zhumell have declined to offer this crucial feature, and the primary mirror sits in a static, non-collimatable cell. Thankfully, the scope holds collimation pretty well over time, but the lack of adjustments is mildly concerning, to say the least, and be prepared for Zhumell to not be of much assistance in replacing or fixing an out-of-collimation scope.
The Z100’s secondary mirror is collimatable, but you shouldn’t ever need to touch it. The primary losing collimation is a far bigger concern.
The Z100’s focuser is a 1.25” rack-and-pinion consisting partially of plastic. It works adequately. The scope attaches to its tabletop Dobsonian mount using a short, metal Vixen dovetail.
Decent accessory offerings for the price
The Z100 comes with two eyepieces: a 17mm Kellner (24x) and a 10mm Kellner (40x). These eyepieces are certainly decent (though they do lack rubber eyecups, which I find annoying) and are made entirely of metal and glass – no plastic to be found, unlike the eyepieces supplied with many cheaper telescopes. The 10mm is, however, rather short on eye relief and its short physical length may result in your nose bumping into the telescope while viewing.
The scope could theoretically take up to 150-200x, but the mount is a little annoying to use above 100x or so, and the optics max out at around 150x from my experience.
The most crucial additional accessory we would recommend for this scope would be a 6mm “gold-line” eyepiece or a 2x Barlow lens. The 6mm Goldline gives you 66x magnification, allowing for better planetary views than with the 40x provided by the stock 10mm Kellner. Alternatively, the 2x Barlow coupled with the stock 10mm eyepiece provides 80x. If you can only pick one, we would recommend the 6mm Goldline, but if you’re able to buy both, you could also buy Barlow with the 6mm eyepiece for an astounding 133x, which is about the practical limit of what this telescope can provide.
The Z100 also includes a standard red dot sight, which works just fine for this telescope.
RECOMMENDED BUY FOR THE ENTIRE PACKAGE
The Z100’s wide field of view at low power (over 2 degrees with the stock 17mm and up to 4 degrees with optional lower power/wider field oculars) makes it extremely easy to find deep-sky objects with little in the way of practice.
The best mount for the price
The Z100 comes on a fairly utilitarian tabletop Dobsonian mount, which it attaches to via a plastic Vixen dovetail saddle. The mount is made mostly of particle board with some sort of laminate glued on, but the azimuth bearings are in fact real Teflon pads. The altitude bearing is not of the conventional Dobsonian design but works nonetheless. Additionally, the mount has a small cutout for use as a handle.
If you don’t have a sturdy enough table or bar stool to set the Z100 on, the bottom of the mount has a ¼ 20 threaded hole, so you can attach it to most photo tripods. You can also set the scope on the hood of your car, which is arguably a more stable option than a lot of cheap tripods or folding tables.
What can you see with the Zhumell Z100?
The Z100 will offer great views of the Moon and decent views of Venus, Mars, Jupiter, and Saturn. Venus will show its phases, Mars its ice caps and maybe a few dark areas in opposition, and Jupiter and Saturn will show their moons and cloud belts. Jupiter’s Great Red Spot is also visible, as are Saturn’s majestic rings and the gap between them known as the Cassini Division. Uranus and Neptune are also visible as tiny bluish dots, but they are a bit tricky to locate.
A small, inexpensive refractor may do a slightly better job on the planets than the Z100, but the Z100’s larger aperture makes it superior for viewing deep-sky objects, and it’s also far more lightweight, compact, and portable than a refractor.
Outside the solar system, the Z100 can show you thousands of double stars and hundreds of open star clusters. You’ll be able to spot globular clusters as fuzzy smudges, a few dozen of the brightest galaxies, and with luck, maybe pick out hints of detail in a few such as the dust lanes in M82 or M31. However, doing this will require dark skies. The Zhumell Z100 is also capable of showing various bright nebulae like Orion, the Lagoon, the Dumbbell, and the Ring, which will look great even from light-polluted skies.
Aftermarket Accessory Recommendations
The Z100 is a great scope, but if you have the budget for accessories at the same time as your purchase we’d recommend you consider the larger Z114 or the Sky-Watcher Heritage 130P instead, as their larger apertures will provide far more of an improvement in views than any aftermarket eyepiece or filter. However, we’ve provided some options here for your convenience.
The stock 17mm Kellner is perfectly adequate for low-power sweeping with the Z100, though it does not maximize the attainable field of view with a 1.25” eyepiece. Unfortunately, the Z100’s f/4 focal ratio means that a 32mm Plossl eyepiece is not ideal, as it will provide too low of a magnification. A 25mm Plossl (16x) provides a lower magnification and wider field than the 17mm Kellner, but the background sky may be too bright for it to be of any real use if you are under light-polluted skies and it will show a lot of coma towards the edges of the field of view.
On the other hand, acquiring a 6mm redline/goldline eyepiece is essential for high-magnification views with the Z100, as the stock 10mm eyepiece only delivers 40x magnification. The 67x provided by a 6mm ocular is at the low end of what is considered to be a useful magnification for observing Mars, Jupiter, and Saturn. A 2x Barlow lens for 133x, or a 4mm planetary eyepiece for 100x, is even better; the Z100 can nominally handle up to 200x magnification but in practice 140x-150x or so is the most that is actually effective to use.
Though undoubtedly quite an expensive purchase for such a small telescope, a UHC/OIII nebula filter can considerably improve your viewing experience of nebulae, most notably the Orion Nebula, when used with the Zhumell Z100. This filter, when paired with the 80AZ under dark skies, allows you to observe vast nebulae like the North America or Veil Nebula, and it’ll transfer over to larger and more powerful telescopes in the future as well.