Optical Overview Of XT8 and XT8 Plus
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.
The Plus boasts having slightly higher reflectivity (94% versus something like 92%) mirrors, but in practice, you are very unlikely to ever notice this.
The XT8 comes with a single eyepiece – a 25mm Plossl. This eyepiece is good for low power, but the 2” Crayford focuser offers you the ability to use wide-field 2” eyepieces so I would recommend replacing the 25mm with one of those. For high power, a few “gold-line” or 82-degree eyepieces are an ideal choice.
The Plus variant replaces the 25mm Plossl with an actually inferior 2” 28mm Kellner which they brand as the “DeepView”. It’s okay at f/5.9 but it’s no better than the 25mm Plossl and offers only a very slightly wider field of view.
The Plus also includes a 10mm Plossl which works well but is a little short on eye relief – a 9mm “gold-line” will be a vast improvement – along with a Barlow lens, which can be used with the 10mm for 240x. However, a dedicated 6mm or shorter eyepiece would be far better than the Barlow and 10mm Plossl.
Orion sometimes sells a “limited edition” XT8 with a red tube. This is basically a regular XT8 with a 35mm DeepView eyepiece (still a Kellner, but a wider field than the 28mm so it actually makes some sense) and the aforementioned Barlow, along with the regular 25mm Plossl eyepiece. These two accessories aren’t really worth the ~$50 price increase over the regular XT8.
The XT8 Plus comes with a safety film (basically an improved, solar-safe Mylar) filter for viewing sunspots, which makes it a solar-compatible telescope. It is certainly enjoyable, but you can, in fact, make your own filter with some Thousand Oaks film and cardboard/plywood for a fraction of the price. Also, an 8” will almost never be able to achieve full resolution during the day for solar viewing due to, well, the heat from the Sun.
The XT8’s focuser is a very nice, if large, 2” Crayford. It is nearly as good as the Moonlite I own – and costs far less. There are no plastic parts on it anywhere. Older XT8s came with a so-so rack-and-pinion focuser with knobs that dug into your skin.
The Plus has a dual-speed, low-profile Crayford focuser that works even better. It’s a very nice focuser but it is a bit of overkill for an 8” telescope at a modest focal ratio. I rarely find myself needing the fine-focus knob.
The XT8’s finderscope is a simple red dot. A finder like this is fine for a small telescope but with a big scope like the SkyQuest XT8/XT8 Plus you really need a 9×50 finder, Telrad, or both to find dim deep-sky objects.
The regular XT8 uses springs for tensioning, 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.
The XT8 Plus actually is a step down from the regular XT8 in this regard, as it uses regular bearings with adjustable tensioning knobs – if your scope is heavy on one side you have no choice but to tighten the altitude axis, which makes motions stiff and awkward. I am utterly perplexed as to why they would remove the springs and swap them out for this.
The Plus has a white trim on the very bottom of the base to help with seeing it in the dark, but it’s so far down that it tends to be buried in the grass anyway, and you could put some glow-in-the-dark or reflective tape on the regular XT8 to do the exact same thing.
The Plus also has a few weight-saving cutouts in the base unlike the regular XT8, but somehow actually comes out weighing slightly more than the regular XT8.
My main gripe with the SkyQuest XT8’s mount beside the small bearings is the fact that it is made of particle board. If you chip the paint/veneer you will expose what is basically pressed-together sawdust which will quickly warp and rot.
Also, particle board 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.
What All Can You See With Orion XT8?
Even from the suburbs, the XT8 shows a lot. The entire Messier catalog (with the possible exceptions of M74 and M33 if you have lots of light pollution) is visible without a lot of difficulties, and you can start diving into the Herschel 400 and other dim deep-sky catalogs.
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.
Neptune’s moon Triton is visible on a decent night, and the lunar crater Clavius shows several dozen craterlets.
The XT8’s tube fits across the backseat of most cars, so portability is not a problem. The tube and base are each only a little over 20 lbs, so most adults will have no issues hauling it.
While the base Orion 8944 SkyQuest XT8 classic dobsonian is somewhat accessory-poor, if it’s at the upper end of your budget it can always be upgraded later at your leisure. Optically and mechanically, it surrenders nothing to more expensive 8” telescopes. An 8” telescope is enough for a lifetime of observing and is still pretty convenient and portable.
The XT8 Plus is not a particularly great deal and actually loses some of the features that make the XT8 great. The included accessories seem to be as much useful as they are a gimmick. Thus, I don’t recommend it over the regular XT8.