The Optical Tube
The XT8 is an 8” f/5.9 Newtonian reflector, a fairly simple design. The primary mirror is made of low-expansion borosilicate glass AKA Pyrex, making it cool down faster than a plate glass mirror. Like most Newtonian reflectors, the XT8’s mirrors have to be aligned (collimated) fairly frequently, although not necessarily every time you use the telescope. This is a relatively easy procedure and not something to be afraid of.
The focuser on the XT8 is a high-quality, single-speed 2” Crayford focuser. There is not a single plastic component to it.
The tube of the XT8 is about 48” (1.2 m) long, and as such fits across the back seat of most vehicles.
SkyQuest XT8 Accessories
The XT8 comes with a single eyepiece – a 25mm Plossl providing 48x magnification. It’s not a bad eyepiece, but you’ll of course want additional eyepieces for higher and lower magnifications, particularly for good views of the Moon and planets.
The XT8’s finderscope is a simple red dot sight. A finder like this is fine for a small telescope but with a big scope like the SkyQuest XT8 you really need a 9×50 finder, Telrad, or both to find dim deep-sky objects.
The XT8 Mount
The SkyQuest XT8 is a Dobsonian telescope, which pivots up-down and left-right on Teflon pads. There are no locks, clutches, gears, or knobs to turn. You just push and pull the scope around the sky. Even at high magnifications, this is surprisingly easy to do and the silky-smooth motions of the telescope make tracking and aiming the scope a breeze.
The regular XT8 uses springs for tensioning the altitude bearings which allow the scope to pivot up and down, as the telescope is prone to tipping over if it is slightly top- or bottom-heavy, due to the small bearings providing a smaller fulcrum and any imbalance making the whole tube act like a lever. This is actually quite helpful, but the springs look a little silly and are difficult to attach and remove.
Our main gripe with the SkyQuest XT8’s mount beside the small bearings is the fact that it is made of particleboard. If you chip the paint/veneer you will expose what is basically pressed-together sawdust which will quickly warp and rot. Also, particleboard is incredibly heavy – the base of the Orion SkyQuest XT8 weighs a little over 20 lbs. Thankfully, if the base is damaged or simply breaks your back, you can make a new base out of ¾” plywood for relatively little money which will weigh less and probably look better, even with modest tools and skills. Several aftermarket vendors also offer custom new bases for your SkyQuest XT8, or indeed any commercial Dobsonian telescope.
Should I buy a used Orion SkyQuest XT8?
The XT8 has been around for 20 years, and not much has changed – older XT8s have a slightly lower quality rack-and-pinion focuser, and the oldest units only have a 1.25” focuser, so expect to pay less for one of these. But if the mirror coatings are in good shape and the base isn’t damaged, there’s not much that can go wrong with a used unit. At worst, you can always build a new base out of plywood for a relatively low cost.
There are a few good alternatives to the SkyQuest XT8 in its price range:
- The Apertura AD8/Zhumell Z8/Orion SkyLine 8 offers significantly better accessories and a better focuser than the XT8 at a price that’s hard to beat compared to adding them to the XT8 a la carte.
- The Sky-Watcher 8” Collapsible Dobsonian comes with a better finderscope than the XT8 and an extra eyepiece too, along with of course a collapsible tube which allows it to fit in more compact vehicles and storage spaces.
- The Sky-Watcher 8” Classic Dobsonian is essentially the same telescope as the XT8, but with an additional eyepiece and a 9×50 finderscope instead of the XT8’s red dot. It also has a slightly lower quality focuser.
What can you see with XT8?
The XT8 can show you a lot, especially under clear and dark skies. However, no matter where you are, the Moon and planets will be fabulous. Tiny lunar details just a few miles across like craters, ridges, and volcanoes known as lunar domes can be seen on a steady night, as can the phases of Mercury and Venus. On Mars, the XT8 will show up to a dozen or so features to the trained eye when Mars is close to Earth. Jupiter’s cloud bands show lots of festoons and swirls. The Galilean moons of Jupiter are no longer mere pinpoints but tiny disks, with hints of color. Saturn shows several moons and intricate cloud bands, along with the Cassini and possibly Encke divisions. Uranus and Neptune are merely bluish-green dots, though you might be able to spot Neptune’s largest moon Triton.
The quality of many deep-sky objects you view with the SkyQuest XT8, or any telescope, will be heavily dependent on the light pollution you live under. Galaxies under dark skies look fabulous with the XT8 – you’ll have no trouble spotting the spiral arms of M51 and M33, the H-II regions of M82 and M101, and all sorts of dust lanes and details in several hundred of the brightest galaxies. But under light-polluted skies, the faint details and sometimes whole galaxies themselves will completely vanish from view. Many large bright nebulae are affected similarly. Open star clusters and globular star clusters, as well as smaller planetary nebulae, aren’t as affected by light pollution. Even from the suburbs, you’ll have no trouble resolving many of the globular clusters like M13 and M15 into individual stars, and open star clusters are still majestic and colorful.