The Mirrors, Focuser, and Tube Ring
The FirstLight 8″ Dobsonian looks like a normal 8″ f/6 Newtonian on a Dobsonian mount. But when you look at the scope more closely, it’s pretty clear that it uses tools and parts from other telescopes in some way. The most obvious parts of this are the large hub for the secondary mirror and the focuser on the telescope. The secondary mirror in the FirstLight 8” is only 2” across, but the holder for it is 2.5” wide. This extra, unnecessary obstruction reduces contrast in the telescope, leading to slightly inferior planetary images. As for why it’s there, the answer is simple: the secondary hub is lifted from Explore Scientific’s 8” f/4 and f/5 Newtonians, which have larger secondary mirrors. While the unnecessary extra obstruction is a bit annoying, it doesn’t seriously impact usage, and unlike most other mass-market Dobsonian telescopes these days, you can collimate the secondary with a Phillips head screwdriver rather than an Allen key; a nice touch.
As for the primary mirror, the primary of the FirstLight 8” is easily collimated with thumbscrews rather than the Philips heads of some other manufacturers. The mirror itself is of high quality, and at both low and high magnifications, it shows beautiful, clear images.
The other major oddity of the Explore Scientific FirstLight 8” Dobsonian is its 2.5” (really 2”) hexagonal rack-and-pinion focuser. This high-quality focuser is lifted, again, from faster Newtonian reflectors intended for imaging. But more importantly, to reach focus with almost any eyepiece, you have to install the extension tube that comes with it. This makes the eyepiece about 8 inches away from the tube wall (the focuser is already unusually tall without the extension). Most Dobsonians have a focal plane only a few inches from the tube wall. Having the focus further out means that the secondary mirror must be bigger than usual, or else wide-angle eyepieces might vignette, and it means the focuser body itself is more likely to sag, and the scope is usually trickier to balance. While sagging isn’t a problem thanks to the 2.5” hex focuser’s high build quality, I can’t help but find this design choice a little strange. Thankfully, it works quite well, despite the unusuality of the arrangement.
The FirstLight 8” Dobsonian also has two finder brackets, one on either side of the focuser. Unfortunately, they only work with Explore Scientific and some Meade finderscopes, so you’ll need an adapter or have to switch them out for standard Synta/Vixen-style finderscope brackets.
Lastly, the FirstLight 8” Dobsonian uses rotatable tube rings with the scope’s altitude bearings screwed onto them rather than having bearings bolted to the tube walls. This not only allows you to slide the tube back and forth for balance (which we’ll go into later) and rotate it to put the eyepiece at a convenient location, but it also means you could take the tube off the Dobsonian mount, attach a dovetail, and put it on an equatorial mount for astrophotography. And thanks to its ridiculous amounts of extra focuser travel, the FirstLight 8” will have no trouble focusing with a DSLR camera and adapter.
The lack of accessories with FirstLight 8″
The FirstLight 8″ Dobsonian’s biggest flaw is that it doesn’t come with many accessories, or at least ones that can be used. The scope comes with a red dot finder and a 25mm “Super Plossl”—the same as many beginner scopes. Unfortunately, both are of extremely low quality.
The included 25mm Plossl is, to me, somewhat horrific. Not only is the eye lens recessed quite a bit into the eyepiece body, which means you basically have to jam your eyeball up against the eyeguard to take in the full view, but the thing seems to be constructed mostly of plastic, and the lenses could be plastic as well. It works but leaves much to be desired compared to the high-quality 25mm Plossls delivered with Orion and Sky-Watcher Dobsonians, which are sharper, more comfortable to use, and generally of higher build quality.
The red dot finder has a tinted plastic window, which makes stars appear quite a bit dimmer when viewed through it, and it is a bit wobbly and doesn’t hold alignment well, making aiming the telescope a bit of a frustrating experience.
Overall, I would say that you will probably be unhappy with the included accessories out of the box and might find the telescope hard to use at all, so it’s definitely worth shopping for additional accessories or considering another telescope altogether.
The Superior-Designed Dobsonian Mount
RECOMMENDED BUY FOR ITS SUPERIOR MOUNT
The FirstLight 8” has a number of design improvements to its mount compared to the other non-premium 8” Dobsonians on the market that make it far superior to its competitors.
For starters, the altitude bearings. Most cheap Dobsonians use plastic circles less than ten inches across, pivoting on nylon pads, which produce mostly smooth motions. But if you put a heavy eyepiece on top of the scope, it will fall over unless it has springs (like the Orion XT and Apertura DT Dobsonians) or magnetic counterweights, which will cause the opposite problem when the heavy eyepiece is taken off. The only other solution is to lock up the altitude axis, which results in sticky, jerky, and stiff motions with the telescope. The Zhumell Dobsonians attempt to work around this problem with ball bearings that slide up and down the telescope tube to adjust for different eyepieces. But they have limited travel, and you’re left with the same drooping/swinging problem unless you either lock up the altitude motions or constantly shift the bearings back and forth when you swap eyepieces.
Rather than adopting either of the aforementioned two (flawed) approaches, the FirstLight 8” has large, semi-circular bearings attached to tube rings. As was mentioned previously, the rings allow you to rotate the tube to put the eyepiece at whatever angle you want. They also have much more travel in either direction to compensate for the bottom/top-heaviness. And the large diameter of the bearings means that the center of gravity of the scope simply doesn’t shift as much relative to the bearings with heavy eyepieces and accessories, which means that you likely won’t have to adjust them at all between eyepieces. The large altitude bearings also have the added advantage of smoother motions than their smaller counterparts on other telescopes, and they look prettier too.
For azimuth, the scope uses a fairly typical melamine-on-Teflon arrangement that works well, though it can be a little jerky when pointing the telescope near the zenith (straight up).
The FirstLight Dobsonian mount also has large cutouts in the base that function as handles.
As for downsides? If you have a really heavy eyepiece or a heavy eyepiece and a heavy finder, you’ll have clearance issues with the tube hitting the base of the scope if you try to balance it correctly. However, the extra imbalance that can’t be completely compensated for by moving the tube could be solved with a relatively small counterweight (or even just by mounting a cooling fan on the back of the scope), so I don’t consider this an issue. The instructions for assembling the base are also a little confusing, with drawings and renders that do not match the actual mount and a convoluted labeling system, but thankfully there aren’t too many things to mess up during assembly, so I wouldn’t recommend worrying much.
Should I buy a Used FirstLight 8” Dobsonian?
If the price reduction compared to buying new is fair, then go for it.
The Explore Scientific FirstLight 8” Dobsonian isn’t a bad choice, but due to its lack of accessories it ends up costing more than you might think to get it completely set up and equipped. As such, there are some alternatives we might recommend in lieu of the FirstLight 8” Dobsonian:
- The Apertura AD8/Zhumell Z8/Orion SkyLine 8 definitely has inferior bearings compared to the FirstLight 8”, but the included 9×50 finder is excellent, as is the pair of quality 2” eyepieces. You also get a dual-speed 2” Crayford focuser, a built-in cooling fan at the back, and an included laser problem.
- The Explore Scientific 10” Hybrid Dobsonian faces the same issues of the FirstLight 8” – that is, a single-speed Crayford focuser and a total lack of usable accessories out of the box – but delivers more performance and is more compact when disassembled for storage/transport.
- The Orion SkyQuest XT8 includes a similarly Spartan set of accessories and features as the FirstLight 8” – though in this case, the included 25mm Plossl eyepiece and red dot finder are at least usable – but it’s available at a lower price tag.
- The Sky-Watcher Virtuoso GTi 150P doesn’t have as much light gathering or resolving power as the FirstLight 8” or other 8” Dobsonians, but comes in a collapsible tube form factor and fits in even a backpack or luggage. It also features full motorized tracking and GoTo and two excellent included eyepieces. The less-expensive Heritage 150P is identical apart from its manual tabletop Dobsonian mount which lacks electronics.
- The Apertura AD10/Zhumell Z10/Orion SkyLine 10 features the same great accessories and features as the AD8 with a negligibly larger form factor or increase in weight. A 10” scope is a lot more capable than an 8”, and you’ll be less tempted to upgrade to a truly monstrous instrument right away.
- The Celestron StarSense Explorer 8” Dobsonian features a similarly basic set of accessories as the Explore Scientific FirstLight or Orion SkyQuest XT8 Classic 8” Dobsonians, but the base is similar to the ES 8” with its cutouts for portability and the scope includes Celestron’s StarSense Explorer technology, which uses your phone’s camera and gyroscopes to help you find your way around the night sky without any bulky motors or batteries.
- The Sky-Watcher 8” FlexTube Dobsonian isn’t significantly lighter or superior to the FirstLight 8” or other options we’ve listed here, but its collapsible tube does save on a little bit of space for storage or transport. The pair of included eyepieces and 9×50 finder are also decent. However, you’ll need a shroud and collimating the scope is annoying as the primary mirror can only be adjusted with a screwdriver.
Aftermarket Accessory Recommendations
The first thing for the FirstLight 8” that I’d recommend is replacing the godawful included red-dot finder with a Telrad or Rigel Quikfinder, either of which will stick directly to the tube without needing to fit the proprietary finder brackets, or you could bite the bullet and buy an Explore Scientific or Meade 9×50 finderscope.
As for eyepiece upgrades, there are a variety of options. If I had to pick three, I’d get 6mm, 9mm, and 15mm “goldlines” for high to medium power, and an eyepiece like the GSO 30mm/40mm SuperView for low power.
You might also want to pick up a collimation tool of some sort, such as the Farpoint Astro laser collimator or a Cheshire.
What can you see with the ES Firstlight 8″ Dob?
The FirstLight’s 8-inch aperture gives you a heck of a lot of resolving power. Jupiter will show a wealth of detail in its cloud bands, along with, of course, the Great Red Spot. Its moons will appear as tiny dots (not starlike pinpoints of light) and cast shadows as they transit the planet. Saturn will show about half a dozen moons, the Cassini division within its rings, and some low-contrast cloud bands. Uranus and Neptune are just tiny blue and turquoise dots, but Neptune’s moon Triton is easy to see, and Uranus’ moons are almost visible if the sky is dark and the visibility is good. Mars will show some dark patches and its ice caps, and Venus and Mercury will always display nothing but their phases. And as with any telescope, the Moon shows a wealth of detail, with features only a few miles across visible.
With an aperture of 8 inches, you can also really get into the world of deep-sky objects. Thousands of galaxies are visible with this scope under dark skies, and a few dozen, such as M51, M82, M33, M101, M63, the Leo Triplet, and others, will show some amount of detail, such as dust lanes or spiral arms. The brighter Messier globular clusters such as M3, M15, M13, M92, and M5 can be resolved, while dimmer ones from the Palomar and NGC catalogs can be spotted as faint smudges. There are also, of course, a half dozen bright emission nebulae such as Orion, the Lagoon, and the Swan, dozens of planetary nebulae, thousands of double stars, and, of course, open star clusters scattered throughout the sky, which will look stunning in an 8” telescope.