The Orion SkyQuest XT4.5 is the smallest of Orion’s XT-series “SkyQuest” Dobsonians, and seldom seen at star parties or astronomy events. It’s a rather niche instrument considering the lower price of shorter 4.5” and even 5” tabletop reflectors, however is a good entry for someone considering a smaller, lower-priced dobsonian.
FEATURES: f/7.9 focal ratio, 900mm focal length 1.25" Rack-and-Pinion, Dobsonian mount, and 228x highest magnification
- XT4.5’s collimation tolerances are a bit more lenient and it is easier to reach focus at high magnifications
- High quality eyepieces that deliver great optics
- Sturdy and reliable through its rock-solid Dobsonian mounting
What We Like
- Great optics
- Easy to collimate
- Good eyepieces
What We Don’t Like
- Narrow field of view
- Low-quality finderscope
- Awkward height not great for a tabletop but too short to stand on its own
How the Orion SkyQuest XT4.5 compares to other products
- Sky-Watcher Heritage 130P – The 130P has a bit more aperture than the XT4.5, as well as a shorter focal length meaning a wider possible field of view, but collimating it is a little bit more challenging and the open tube poses some issues such as stray light and moisture intrusion.
- Zhumell Z114 – The Z114 is cheaper than the XT4.5 and offers identical views of the Moon, planets, and deep-sky objects for the most part. However, the edges of the field of view at low power suffer from quite a bit of coma and collimation is a bit more difficult. The Z114 also needs a taller table or stand than the XT4.5 or larger instruments.
- Sky-Watcher Heritage 150P – The Heritage 150P has a collapsible tube as with the 130P, making it a bit more compact and portable. The 6” of aperture also makes it a lot more capable than the XT4.5. However, the downsides of a collapsible tube remain.
- Orion SkyScanner 100 – The SkyScanner’s optical quality is a bit more variable than the XT4.5, and it is not able to be collimated by the user. However, it’s still quite sharp and has only slightly less light gathering ability, it’s a bit more compact, the field of view is wider and the scope can be easily mounted atop a sturdy standard photo tripod with ¼ 20 threads.
The Optical Tube Assembly
The XT4.5 is a 114mm (4.5”) f/7.9 Newtonian reflector with a focal length of 910mm. This optical configuration is fairly common in low-cost “department store” telescopes such as the Celestron PowerSeeker 114EQ; they all have good optics but are unfortunately bundled with low-quality accessories and a shaky mount.
The XT4.5 thankfully does not suffer this fate thanks to the high-quality included eyepieces and its rock-solid Dobsonian mounting. The mirrors in these scopes are spherical, but a 4.5” f/7.9 sphere is well within the manufacturing tolerances of a typical parabolic mirror anyway and thus boasts very sharp images nonetheless.
Thanks to its longer focal ratio compared to the f/4 and f/5 tabletop Dobsonians that dominate the market, the XT4.5’s collimation tolerances are a bit more lenient and it is easier to reach focus at high magnifications.
The scope also doesn’t have any coma at the edge of the field of view, on account of having a much narrower one in the first place – a 1.25” eyepiece can only achieve a field of view of up to 1.8 degrees in the XT4.5 thanks to its longer focal length, whereas a faster scope like Orion’s StarBlast or the Zhumell Z114 can get up to 3.6 degrees. The longer focal ratio and less shallow depth of field also means the XT4.5 performs better with inexpensive eyepieces such as the provided Sirius Plossls compared to a faster scope.
The XT4.5’s primary mirror is easily collimated without tools. The secondary mirror requires a hex key to collimate, but will likely rarely need any adjustments. The scope also has a carry handle and a grab knob on the end of the tube – larger reflectors tend to just be moved by grabbing the end of the tube, but doing this with the XT4.5 can obstruct the aperture due to its small size, hence the knob.
The length of the SkyQuest XT4.5’s tube and the bulky frame of the mount mean it’s not nearly as compact as shorter and/or collapsible tabletop offerings. You can’t fit it in a backpack or carryon luggage on a plane, and it does need a fair amount of space to be transported in a vehicle, too.
The XT4.5’s mount is a pretty standard Dobsonian design. The scope pivots up and down on two plastic-on-Teflon bearings. To help alleviate balance troubles with heavier eyepieces as well as keep the scope held down due to its lightweight, the XT4.5 uses Orion’s spring tensioning system to fasten it to the rocker box when in use.
The mount is basically a miniature of Orion’s larger instruments; a thinner particle board is used but it’s still the same melamine-covered stuff. The mount has an eyepiece rack attached to the side as well.
To keep it steady, the XT4.5’s ground board is a bit wider than the rest of the mount. This unfortunately does mean it can be hard to find a suitable table or stool to set the scope on. However, with a nearly 1-meter long optical tube, you really only need something like a milk crate to elevate the SkyQuest XT4.5 to a suitable height for seated observing or for children to look through it.
The Scopes Accessories
The XT4.5 comes with two 1.25” barrel diameter Plossl eyepieces, which Orion dubs the Sirius line. They have focal lengths of 25mm and 10mm, thus providing 36x and 91x respectively. These eyepieces have no plastic components and are quite well-made, providing sharp images. However, the 10mm is a bit short on eye relief, requiring you to practically jam your eyeball into the eye lens in order to take in the entire field of view and get your eyelashes out of the way.
This can make it a bit uncomfortable to use. 91x is enough magnification for planetary viewing, but this scope can handle up to 200x so we might recommend something like a 6mm “goldline” (which would provide 152x with the SkyQuest XT.45) or even a 4.5mm planetary eyepiece (202x) to complement the stock oculars. The 25mm Plossl provides a 1.5-degree true field of view with the XT4.5, which is a bit narrow for scanning for deep-sky objects. A 32mm or 40mm Plossl will provide a bit lower magnification and a field of view of about 1.8 degrees.
The biggest drawback of the XT4.5 is undoubtedly the finderscope. For whatever reason, Orion has elected to provide a 6x26mm finderscope with a built-in erecting prism. 26mm is simply not enough aperture for a finderscope to show you much of anything, the prism sucks up even more light, and the finder is uncomfortable to look through unless you are aiming the XT4.5 near the horizon. As such, we’d recommend replacing it.
A 40mm or 50mm right-angle finder may be overkill, but will show stars fainter than what you can see with the naked eye and is a lot more comfortable to look through. A simple red dot is a cheaper and simpler option which will also suffice. Either should slot into the shoe/base on the SkyQuest XT4.5’s optical tube. You could also add the superior Rigel QuikFinder or Telrad, though the latter will look especially silly attached to such a small instrument.
Lastly, the SkyQuest XT4.5 includes a simple collimation cap to help you easily collimate the telescope.
Orion offers an “accessory kit” upgrade for the XT4.5 as well. This includes a nice 2x Barlow lens, a red flashlight, a Moon map, a planisphere, and an “observing guide”. The Barlow is nice and will provide 194x when used with the 10mm Sirius Plossl, but as the 10mm Sirius is quite uncomfortable to use in the first place, a dedicated higher-power eyepiece is probably better instead.
The flashlight can be purchased elsewhere for less, and the included reading material is more of a decorative touch than anything particularly useful for actually using under the night sky with the SkyQuest XT4.5 anyway.
Orion SkyQuest XT4.5 Specs Table
What Can You See With Orion SkyQuest XT4.5
The XT4.5 is best as a lunar and planetary instrument, though, as always, it’s limited by its small aperture and the steadiness of the atmosphere. You should be able to easily see the phases of Mercury and Venus, the rings of Saturn, and Jupiter’s cloud belts and moons.
Our own Moon looks spectacular, with the SkyQuest XT4.5 showing details such as mountain peaks, crater rims, valleys, ridges, and cracks just a few miles across in size. Under steady skies and at higher magnification, Jupiter’s Great Red Spot can be seen, and the four Galilean moons can be resolved as tiny disks when they transit across the planet, with their black shadows following behind.
Saturn’s rings reveal the Cassini division within them at higher magnifications, and you can also see up to a half dozen moons around the ringed planet – ranging from the bright and easily spotted Titan to 13th-magnitude Enceladus.
Saturn itself also has some rather bland-looking cloud belts. Uranus and Neptune are bluish-green fuzzes barely distinguishable from a nearby star of similar brightness, as they are too small to resolve clearly with most backyard telescopes and their moons are too dim for the small aperture of the SkyQuest XT4.5 to pick up.
You can forget about Pluto, too, as it too is simply too dim to catch even under perfectly dark skies.
With 4.5” of aperture, the SkyQuest XT4.5 can somewhat resolve the outer parts of globular star clusters even under subpar skies. The easiest clusters like M13, M92, M3, M22, M15, and M5 (and, of course, Omega Centauri) should be easily distinguishable from mere fuzzy balls. Smaller, dimmer, and more distant globulars are a bit more difficult. Open star clusters dazzle regardless of your viewing conditions, and hundreds can be viewed with the SkyQuest XT4.5.
Nebulae such as the Orion Nebula (M42) and the Swan (M17) look great, even under somewhat light-polluted skies. A good nebula filter will greatly improve the view, however. Smaller planetary nebulae are out of reach, but big and bright ones like the Ring (M57) and Dumbbell (M27) look nice.
Galaxies are likely to somewhat disappoint due to the XT4.5’s small aperture, but under dark skies, you can see dust lanes in a few of them, such as M82 or M64, or the Andromeda Galaxy, M31. Large galaxies like M31 also tend to have smaller companion galaxies surrounding them which can be seen.
You should be able to see a couple dozen galaxies within a few degrees of each other in the Virgo Cluster, too. Under light-polluted skies, however, seeing galaxies at all, let alone resolving any detail in them, is going to be a challenge with any telescope, especially a small one like the XT4.5.
And regardless of conditions, the SkyQuest XT4.5 simply doesn’t have enough aperture to clearly resolve spiral arms in galaxies, and you’re limited to viewing them at low magnifications, which are unlikely to show much detail – increasing the magnification makes them dimmer as their light is spread out over a large area, and thus many become almost completely invisible at high power even if they were easy to spot at lower magnifications.
Lastly, the SkyQuest XT4.5 is also pretty good at splitting double stars. Hundreds of them can be seen even from a city sky, and pairs that are extremely close together are a good test of your atmospheric conditions, collimation, and your own skill as an observer.
Final Thoughts on Orion SkyQuest XT4.5
Overall, the Orion SkyQuest XT4.5 is a pretty good telescope, aside from its poor-quality finderscope and the awkwardness of a tabletop telescope with a long tube. There are slightly better deals for the money, and a bigger 5” or 6” Dobsonian, even a tabletop, will show you more. But the XT4.5 isn’t a bad choice, especially if you can get a good deal on one or you mainly want to observe the Moon, planets, and double stars where perfect resolving power and convenience is more important than bright views of faint fuzzies or a wide field of view.
If aperture is more your thing, however, we’d definitely consider taking a look at either a 5” or 6” tabletop telescopes such as the Zhumell Z114/Z130, the Sky-Watcher Heritage line, or the Orion StarBlast 6. A bigger Dobsonian in the 6-10” aperture range will prove to be a lot more bulky but vastly more powerful than a small tabletop instrument such as the SkyQuest XT4.5, and a 6” scope isn’t a massive step up in price or complexity compared to the XT4.5 either.