What makes this scope different?
The main factor that makes this 10-inch Dobsonian different is that it is a truss telescope. In the past, telescopes and, for that matter, almost all commercial Dobsonians were what’s known as solid tube. A solid tube telescope is one where the tube that holds the mirrors is completely solid, typically metal or, in some cases, wood. A truss-style telescope is almost completely different, as it is constructed with truss poles. This means that there is no tube at all. How can that be? Won’t light spill into the telescope? I will answer that here, and also explain why it can be very advantageous.
A truss telescope consists of four major parts: the base/rocker box, the mirror box, the truss poles, and the upper tube assembly. The rocker box in a truss telescope is the part that contains the bearings to move the telescope up, down, left, and right, and it is what the telescope sits on. Because the truss telescope design has a much different centre of gravity, the rocker box can be very short.
Next is the mirror box, and it is, as the name implies, where the main mirror is located. The mirror box is typically very short as it does not do much more than hold the mirror in and collimate the mirror. The mirror box is where the altitude bearings attach, as they pivot up and down. The truss poles attach to the top of the mirror box.
The upper tube assembly sits on top of the truss poles, and it holds the secondary mirror, finderscope, and focuser of the telescope. Typically, the upper tube assembly is formed of two lightweight rings with struts in between, as you will find on this telescope. The upper tube assembly is also very light as it is almost completely hollow while still being quite strong.
The truss poles are the main feature in a telescope like this. Truss poles replace the typically very heavy metal tubes that become impractical for large telescopes, and they make the telescope far more portable. Truss poles are the set of eight poles that form a triangular shape (hence the name truss) and make the telescope extremely rigid-perhaps more rigid than a closed tube telescope. The truss poles detach from the upper and lower sections of the telescope easily, leaving only the lower and upper tube assemblies, which themselves are very small. The poles make up the bulk of the telescope’s length but are quite small. These factors make truss telescopes extremely portable and lightweight.
The Explore Scientific 10 inch dob, while being a truss-style telescope, is still a Newtonian reflector type telescope with some basic features that you will find across most telescopes that you should know before considering purchasing this scope. I will list them here.
- The Explore Scientific 10” Truss Dob is, as the name states, a 10-inch Dobsonian. This means that the primary mirror has a diameter of 250 mm, or 10 inches. A 10-inch dob is on the verge of a “large” Dobsonian, as it will reveal some of the darker objects like faint galaxies under dark skies but may not show them in great detail. Luckily, Explore Scientific makes larger Dobsonians, up to a staggering 20 inches.
- The ES 10” has a focal length of 1250mm, which is f/5 when you consider the 10-inch primary mirror. F5 is a decent speed for a 10-inch telescope, as it is usable for both planetary and deep-sky observing comfortably, while still being short enough to use without a ladder. Because of that, the F/5 focal ratio also does not create as much coma as a faster mirror, and because of that, you do not need an expensive coma corrector to remove distracting aberrations.
- The best feature that the truss design brings about is the extremely lightweight and portable telescope. As the large, heavy tube is ditched for eight poles, the truss design allows this telescope to be far lighter and far smaller than its alternatives. This scope weighs 59 pounds and it packs down into an extremely small space. Solid tube Dobsonians would be much harder to transport, as the rocker box is much larger, and the tube itself is very long.
The Explore Scientific Dobsonians are well known for including high-quality accessories with their telescopes that improve the ease of use and quality of viewing. Some of the accessories can greatly improve your observing experience, so I will list them here.
- The ES 10” dob includes a red dot finder. A red dot finder is useful to use on a telescope to locate and move targets in the night sky. The red dot finder included projects a simple red dot onto a glass screen, which you look through and centre the target you wish to view in the red dot. In my opinion, something like a Telrad finder is much improved, but a red-dot finder gets the job done without being extremely heavy.
- The dob includes a high-quality 2-inch focuser, which is fairly high quality and smooth, and accepts 2-inch eyepieces and 1.25-inch eyepieces with no trouble. The focuser includes a dual-speed knob, which allows you to focus more finely. It is not a terrible focuser, and in my opinion, unless something is wrong, you do not need to upgrade it.
- The telescope includes mirror cooling fans that are incorporated into the box. These fans allow you to cool the mirror quite quickly at night, so the views are not compromised by a changing mirror shape. Fans also have the advantage of blowing away any would-be dew that could land on the mirror surface, ruining views.
- The telescope has an optional shroud. A shroud is a large piece of fabric that goes around the truss poles and blocks any light that would ruin views. The shroud can help deter dew, but it is most important if you observe in areas that have bright streetlights that could seriously impact viewing if they shone directly onto the primary mirror. However, it is an additional expense you’ll have to factor in when purchasing this scope.
Using the Truss Dobsonian
The Explore Scientific 10” Dob, being a truss tube, has some fairly major changes in operation compared to other telescopes, but also includes a novel form of collimation. Here I will go over the whole process of operation needed to set up this telescope and the front collimation feature. The ease of setup is what makes the truss-style tube an interesting alternative to solid tube telescopes, even if it needs more setup steps.
The ES10 begins with laying down the mirror box. You then attach the altitude bearings (which are removable, which makes transport easier as altitude bearings are very large, especially the oversized ones on this telescope). You can mount the altitude bearings at different positions to take into account different eyepiece weights so the telescope does not become unbalanced.
Next, you install the truss poles at four locations on the mirror box. The truss poles come in pairs, so they stay together reasonably well in transport. If you use the same poles at the same locations, you can reasonably maintain collimation when taking down and setting the telescope back up. The poles are attached with easy-to-use thumbscrews.
Next, the upper tube assembly is attached to the top of the 4 truss poles, also with thumbscrews. At this point, the actual assembly is complete.
Then comes the collimation of the mirrors. A great feature found in the Explore Scientific line of truss telescopes is that the primary mirror is collimatable from the front of the telescope. This means that you no longer have to reach to the back of the telescope, risking bumping the telescope and walking back and forth between the eyepiece and the mirror box. Instead, the ES dob includes a tool to collimate the telescope from the eyepiece, so you do not have to reach down to the mirror cell. This, paired with the secondary’s large adjustment knobs, makes this telescope extremely easy to collimate. After you collimate, you are all good to go.
Aftermarket Accessory Recommendations
The first thing you should probably do for this scope if you don’t already have eyepieces is get some. At a minimum, we’d recommend three to start out with. Here are our picks:
- GSO 30mm SuperView (42x): Good low-power eyepiece for finding targets and viewing larger ones such as emission nebulae and star clusters.
- GSO 15mm SuperView (83x): Good medium-power eyepiece for general viewing of most objects.
- 6mm “goldline” (208x): High-magnification eyepiece for the Moon, planets, double stars, globular star clusters, and planetary nebulae.
If you’ve got a little more money left in the budget, we’d also recommend something in the 8-11mm range and 18-24mm range for moderate magnifications.
Next up, you pretty much need the accessories ES offers for the scope in order to actually use it:
- Shroud – Keeps light and moisture out of the tube, and curious hands from touching the optics, or stuff from being dropped on the primary.
- Counterweight kit – Properly balances the telescope.
In conclusion to this review, I believe that the Explore Scientific 10” truss Dobsonian telescope is one of the best portable scopes released in recent years. At a relatively cheap price, it is sure to be a great choice for anyone wanting to start getting into deep sky observing.
The ES 10” is a very portable and lightweight telescope thanks to the truss-style construction, while still being able to handle heavy eyepieces and accessories. The truss-style is also very compact and can shrink down to an incredibly small form factor which makes this telescope east to move around. In conclusion, I highly recommend this 10-inch Dobsonian to anyone who has the budget for it as it is an excellent all-round performer.