The Optical Tube
The Apertura AD6 is a Newtonian reflecting telescope, a common design characteristic of most Dobsonians with a parabolic primary mirror to focus light onto a flat secondary, which in turn forms an image at the eyepiece. As the name suggests, the AD6 features a 6” (152mm) f/8 primary mirror with a 1200 mm focal length and thus a focal ratio of f/8. 6” f/8 reflectors are popular and affordable options for beginners because they are easy to produce and have less stringent manufacturing and optical tolerances across the board. A 6″ f/8 parabolic primary mirror is easier to grind and polish than a faster mirror. Also, a slower focal ratio means you do not have to worry about precise collimation or aberrations caused by cheaper eyepieces like the Plossls that come with the kit. The 48” long tube of the AD6 can fit across the back seat of most cars, although it may not fit in smaller trunks. The eyepiece is usually positioned at a comfortable height for seated observers.
The AD6 and other Dobsonian telescopes made by the Taiwan-based Guan Sheng Optical (GSO) have a primary mirror made of BK7 optical glass, which is similar to regular soda-lime plate glass in terms of its thermal and mechanical properties. At this relatively small aperture, the cooldown differences of this material compared to a low-expansion material like borosilicate glass (Pyrex) are irrelevant. The AD6’s mirror will acclimate rapidly to cooler nighttime temperatures without a fan (of which none is provided, unlike with Apertura’s larger Dobs).
The AD6’s primary mirror collimation is, thankfully, adjustable without tools. Like the Apertura AD8, AD10, and AD12, there are 3 spring-loaded knobs to adjust collimation and 3 “locking screws”. Remove the locking screws. You’ll be happy you did. If you do find the AD6 shifts in primary mirror collimation frequently, you can always order stiffer springs for the primary mirror cell. Enough said. The secondary mirror’s tip and tilt is adjusted with a hex key, one of which is supplied with the telescope. You can buy aftermarket thumb screws for the secondary mirror, but we don’t recommend this. With the stock screws, it will likely seldom, if ever, need adjustment anyway. Thumb screws will just make it go out of alignment more often.
The Apertura AD6 incorporates a robust 2” GSO dual-speed Crayford focuser. This is the same model of focuser used on other GSO-made scopes, including the Apertura AD Dobsonian line, various Newtonian astrographs, and their Cassegrain/R-C scopes. Like all Crayfords, this focuser operates by moving the focuser draw tube against four precise rollers and a strip of Teflon (PTFE) plastic. At f/8, the precision required for sharp focus is much lower, and thus the 1:10 fine adjustment knob of this focuser is arguably overkill, but it’s nice to have anyway.
The GSO dual-speed Crayford focuser employs a brass compression ring to securely hold eyepieces, and the AD6 includes a 1.25” adapter equipped with its own compression ring. As with the other Apertura AD Dobsonians, you also need to use the provided 35mm extension tube (itself with a compression ring) for the AD6 to reach focus with most eyepieces/accessories.
The Apertura AD6 comes equipped with two 1.25” Plossl eyepieces made by GSO. There’s a 25mm eyepiece offering 48x magnification with the AD6, and a 9mm variant for a higher 133x magnification. Both eyepieces are of decent build quality, provide crisp images, boast blackened lens edges, and are entirely devoid of plastic components internally. They present an apparent field of about 52 degrees. The 9mm eyepiece, following the Plossl blueprint, has somewhat limited eye relief, which will mean getting your eye closer than is entirely comfortable to grasp the full view. A 9mm aftermarket eyepiece such as the redline/goldline with greater eye relief is more comfortable to use on a regular basis or if you commonly share the view with other people.
To aim the AD6, Apertura includes a conventional 6×30 finder scope. This attaches to the AD6 utilizing a common Synta-style bracket, fostering easy swapping with other finder scopes such as a larger aftermarket 9×50 or a red dot sight. The AD6’s 6×30 finder offers a true field that’s roughly 7 degrees wide, akin to what you’d experience with typical wide-angle 7×35 or 7×50 binoculars. Its perspective is not inverted, flipped left-right or up-down (hence the correct image moniker). The crosshairs in the eyepiece are not illuminated and can be a little hard to see in the dark, but this finder will do the job.
The Apertura AD6 is a Dobsonian telescope and thus utilizes the alt-azimuth Dobsonian mount design: a predominantly wooden base in which the telescope pivots up and down like a cannon and swivels left to right with a bottom board that rests directly on the ground. Dobsonian mounts are easy to use, extremely sturdy, quick to set up, and cheap to make. The AD6 is not perfectly smooth on the azimuth (left-right) axis by default, but it’s easy and cheap to upgrade it with Teflon pads for buttery-smooth motions on both the altitude and azimuth axes.
For its azimuth (side-to-side) movement, the Apertura AD Dobsonians employ roller bearings in between the two bottom boards, which essentially function like a “lazy Susan.” While smooth enough, the use of this bearing means that the AD6 arguably swivels a little too easily; tightening the center bolt will lead to jerky motions rather than a more fluid movement at high magnifications. Most Dobsonians use the friction of the bottom board gliding on three Teflon pads to achieve smooth motions without being prone to bouncing or overshooting the target.
The relatively light weight of the AD6 exacerbates the too-light nature of the Apertura Dobsonians’ azimuth bearings. The rollers are tolerable with the AD8 and AD10, but not with the AD6. You will find making tracking adjustments at high magnification to be somewhere between annoying and impossible, especially given the narrow field of view of the stock 9mm Plossl eyepiece. Thus, we would strongly recommend you just swap the roller assembly for three Teflon pads nailed to the bottom board above the feet of the telescope. You can buy Teflon yourself and cut it, or use furniture glides, and there are kits made for the Apertura telescopes as well.
The altitude bearings of the AD6 are likewise of the same design as those utilized by the larger Apertura Dobsonians. Each bearing consists of a ball bearing assembly enclosed within a metal housing with a large plastic knob to adjust friction, which in turn slots into cutouts on each side of the base. The bearings each slide on a track on the side of the AD6 optical tube, allowing you to move them a couple of inches forward/backward to balance the telescope with different accessories. While a bit unusual and departing from the normal arrangement utilized by Dobsonians, the altitude motions of the AD6 are plenty smooth, and there is enough room for adjustment that the scope won’t wind up too top-heavy even with a 9×50 finder and 2” eyepieces.
All being said, the major downside of the AD6’s mount is its weight. Like most commercial Dobs, this one assembles out of a bunch of melamine-coated particle board pieces, which you screw together with a hex key like you would a piece of IKEA furniture. The particle board is very heavy per square inch, however, and there is little weight optimization for the AD6. The ground board is unnecessarily a full circle rather than a more lightweight triangle, which adds several pounds. As a result, the AD6’s base weighs just a couple pounds less than that of the larger AD8 and AD10 models, and in total, the AD6 is less than 10 pounds lighter than the AD8. You could make or buy a replacement plywood base, but that money could’ve gone into a larger scope or accessories.
Should I buy a used Apertura AD6?
A pre-owned Apertura AD6 Dobsonian is indeed a fantastic investment for stargazing enthusiasts. It’s essential to inspect the mirrors to ensure they retain their reflectivity and are not transparent. A certain amount of dirt or surface residue is acceptable and is likely removable with careful cleaning. However, any visible damage to the coating signifies a requirement for mirror recoating. Such an added expense could offset the financial benefits gained from purchasing the telescope secondhand.
Any damage to the base shouldn’t be a deterrent, though a sufficiently unusable or missing base should be reflected with a substantial discount on a used scope. The good news is that a Dobsonian base is one of the easiest carpentry projects in existence; constructing a replacement base using plywood is both cost-effective and uncomplicated with even the most basic tools or a CNC. A homemade plywood base often proves lighter than the original, especially if you can be bothered to add any cutouts to the sides of the rocker box and opt for a square base over a wide circle.
The AD6 faces stiff competition, not so much from the other 6” f/8 Dobsonians in its price range but rather from the more cost-effective 6” f/’5 tabletops and the 8” Dobsonians like Apertura’s own AD8, which have a negligibly larger form factor than a 6” f/8 like the AD6 but offer considerably greater capabilities.
- The Sky-Watcher Virtuoso GTi 150P is a 6” f/5 Dobsonian with fully automated GoTo capabilities, all packaged neatly in a compact and lightweight design with a collapsible tube. Notably, it offers the flexibility of allowing you to aim the telescope manually even when the mount is powered on and aligned. The 150P is operated via your smartphone or tablet and works on a tabletop or attached to any tripod with a ⅜” stud. Equipped with quality optics and well-crafted eyepieces, the Virtuoso GTi 150P is priced competitively, similar to most manual telescopes of its aperture, such as the Apertura AD6.
- The Orion SkyQuest XT6 features the same basic design, optics, and 2” capability as the AD6, but lacks the AD6’s high-quality dual-speed focuser and is similarly heavy/bulky.
- The Sky-Watcher Heritage 150P is identical to the GTi 150P but lacks electronics or an adapter to attach to a photo tripod. However, it’s considerably cheaper than any other 6” Dobsonian out there.
- Another tabletop Dobsonian, the Orion StarBlast 6, matches the specs and capabilities of the Sky-Watcher Heritage/Virtuoso GTi 150P but features an enclosed optical tube equipped with rotatable rings. Additionally, its 2” focuser allows you to use a coma corrector and 2” eyepieces, providing a wider field of view than any of the other commercially available 6” reflectors. However, the cost of these additional accessories will surpass that of the StarBlast 6 itself, and aside from the 2” focuser, there are few reasons to pick the StarBlast over the Virtuoso GTi/Heritage 150P.
- The Apertura AD8 (also sold as the Zhumell Z8 and Orion SkyLine 8) has the same broad mechanical design and features as the AD6, but with a 30mm, 2” wide-angle eyepiece, a larger 9×50 finder scope, a built-in cooling fan, and, of course, a larger 8” aperture—while weighing just a few pounds more and occupying the same amount of space.
- The Celestron StarSense Explorer 8” Dobsonian may not have the bells and whistles of the Apertura Dobsonians, but it does feature a lightweight base, built-in handles, and Celestron’s StarSense Explorer technology to assist you in navigating around the night sky.
Aftermarket Accessory Recommendations
The Apertura AD6’s stock 25mm Plossl eyepiece is fine, but you’ll want to replace the 9mm Plossl with something more comfortable, namely, a 9mm redline or goldline, which offers the same magnification and equally sharp views but with a wider 70-degree apparent field and longer eye relief. And while you’re at it, consider bridging the gap with a medium-power eyepiece. A 15mm SWA or redline will yield 80x magnification—a balanced power suitable for moongazing and various deep-sky objects. Meanwhile, a 6mm goldline ocular can push the AD6 up to 200x, ideal for viewing the Moon, planets, and close double stars on a clear and steady night.
At the low-power end, you’ve got plenty of options for wide-angle 2” eyepieces thanks to the AD6’s relatively forgiving f/8 focal ratio. A 42mm GSO SuperView (29x) or 38mm Apertura SWA (32x) will maximize the field of view you can get out of this scope.
Although a 9×50 finder scope might seem like a tempting enhancement over the AD6’s bundled 6×30, you may not like the discomfort of a straight-through finder or the confusion of a right-angle unit. Those who fancy a red dot finder can easily slot it into the existing bracket; there are dual finderscope adapters that will allow you to use a red dot alongside the provided 6×30 RACI too. Or you can purchase a proper reflex sight like the Telrad or Rigel QuikFinder, which attaches separately to the tube with its own bracket/base.
Since the Apertura AD6 doesn’t come supplied with any collimation tools, one is needed for this scope. At f/8, a simple “collimation cap” or Cheshire, such as the 2” Cheshire offered by Farpoint, is more than ample to do the job. Our collimation guide explains more, as well as how to precisely collimate the AD6 or another telescope on a defocused star without any other tools in a pinch.
Finally, we would highly recommend a good UHC nebula filter, such as the Orion UltraBlock. A 2” filter can screw onto the AD6’s supplied adapter for use with 1.25” eyepieces. All nebula filters work by dimming the background sky and only allowing specific wavelengths of light through. However, they’re not a cure-all for light pollution and only work on nebulae. A UHC like the UltraBlock won’t help with galaxies or star clusters, and the best views of any of these objects with the AD6 will still be under a pristine, dark sky.
High Point/Apertura offers a few accessories on the purchase page for the AD6. Chief among these are a Cheshire collimator, the 2” 2x ED Barlow lens, and a case. The case isn’t necessary; there are better uses for your money. The Cheshire is a solid choice. The GSO 2” 2x ED Barlow is nice, but you should consider reading our Best Barlow Lenses article and consider whether a barlow, especially a bulky and more costly 2” Barlow lens, is really what you need for observing with the AD6.
What can you see with the Apertura AD6?
The Apertura AD6’s prowess in capturing views of deep-sky objects is, predictably, influenced by the level of ambient light pollution in your vicinity.
Bright open clusters, such as the Double Cluster or the Pleiades (M45), radiate brilliantly without appearing washed out. Through the Apertura AD6, these clusters always impress; however, an environment with minimal light pollution will unveil a richer tapestry of stars with more pronounced colors than the view from within a city. When it comes to observing globular star clusters like M13 or M15, the AD6 does an excellent job, revealing individual stars distinctly at higher magnifications, though you’ll again have an easier time in less light-polluted settings.
A 6” telescope is also big enough to go after some galaxies; virtually the entire Messier catalog is easily within reach in a suburban neighborhood, while the AD6 will be able to reveal all of the Herschel 400 catalog of galaxies under a dark sky. Even under ideal conditions, however, most galaxies lack much in the way of detail, exceptions being the high-contrast dust lanes in galaxies like M82 and M31. Hints of spiral arms can be seen in M51, the Whirlpool, and perhaps nearby M101 or M33, but only to the trained eye and under good conditions. A larger telescope like Apertura’s own AD8, AD10, or AD12 is a better choice than the AD6 in this department.
The AD6 will show you the big and bright planetary nebulae such as M57 (the Ring) and M27 (the Dumbbell) but also numerous smaller ones, such as the eponymous Blinking Planetary and the vivid green Cat’s Eye Nebula. When atmospheric conditions permit, you’ll also be able to split double stars less than 1 arc second apart with the AD6 and a suitable high-power eyepiece; the scope’s dual-speed focuser makes it even easier to get crisp, pinpoint stars at high magnifications.
Planetary observation is another forte of the Apertura AD6. The Moon of course delights with its thousands of craters, mountains, and ridges, with the AD6 revealing details only a few miles across on a steady night. Further out, any good 6” telescope allows you to view the phases of Mercury and Venus, as well as the polar ice caps of Mars. More detail on Mars is evident when the Red Planet is at its closest to us. During these periods, occasional Martian dust storms and a few of its dark features become evident with the AD6 at high magnifications on a steady night.
Jupiter’s moons are discernible in the 6×30 finder scope of the AD6, and as they cross Jupiter, their disks and accompanying shadows become evident through the telescope at high magnifications. The gas giant’s vibrant cloud belts, ever-evolving storm patterns, and the iconic Great Red Spot can be appreciated on nights with clear, stable atmospheres.
Saturn, with its majestic rings, comes alive through the AD6. On nights of good atmospheric conditions, the delicate Cassini Division is discernible, dividing the rings. Alongside, Saturn’s cloud belts and the planet’s shadow on its rings emerge, accompanied by several of its moons, with Titan and Rhea shining the brightest.
While the Apertura AD6 allows for a glimpse of Uranus’s teal disk, its faint moons require at least 8-10” of aperture to be spotted, and the planet itself is too tiny to reveal much detail in its atmosphere. Neptune similarly appears as a yet-smaller bluish dot, though you may be able to spot its moon Triton alongside it with the AD6. Pluto is too dim to spot with the AD6; it has retreated too far from the Sun to be visible with only a 6” telescope, even under pristine conditions, for the remainder of this century.