The Optical Tube
The Sky-Watcher Heritage 100P is a 100mm (3.93”) f/4 Newtonian reflector with a 400mm focal length. Compared to a small refractor, this scope has quite a bit more light-gathering and resolving power, as well as no chromatic aberration, since it is of course a reflector. However, you do not get nearly as much light-gathering power as a 114mm, 130mm or larger Dobsonian with this telescope and those instruments will perform at least a little bit better on high-resolution targets like the Moon, planets, and double stars as well.
At such a fast focal ratio, the 100P also is very hard on eyepieces, and pretty much any low-power ocular will show coma towards the edges of the field of view, which you cannot do much about – all coma correctors cost more than the 100P itself and will not fit. Furthermore, low-cost, simply designed eyepieces such as the provided ones or anything you’re likely to equip the 100P with will show issues like astigmatism or field curvature more readily, but you may or may not notice these much and for the price and capabilities these are more than acceptable compromises.
With a fast f/4 focal ratio, precise collimation of the 100P is absolutely vital for achieving optimal performance with any reflector telescope. Regrettably, as with the Star Discovery 150P and some of the other 100mm and 114mm tabletop Dobsonians, Sky-Watcher has chosen not to incorporate this essential feature, resulting in the primary mirror being housed within a fixed, non-collimatable cell that it is more or less permanently glued to.
Although the telescope maintains its collimation reasonably well over time, and usually will arrive well-collimated, the absence of adjustments is, at the very least, a cause for concern. You can adjust the 100P’s secondary mirror collimation with a screwdriver, but this is hardly ever necessary. If the primary mirrors goes or arrives out of collimation, you can widen the holes its holder attaches to the tube with to sort of tip/tilt it yourself but it will otherwise need to be sent back to the manufacturer. The larger Heritage 130P and 150P do not have this issue and are readily collimated by the user.
The Heritage 100P uses a 1.25” rack-and-pinion focuser, made entirely out of plastic. While not perfect, it works well enough with the 100P and provided eyepieces, and for the price we can’t really complain.
To attach to its provided mount or any astronomical mount or tripod, the Heritage 100P features a metal Vixen-style dovetail bar attached to the side of the tube, allowing it to be attached and removed from a mount without any tools or adapters.
The Sky-Watcher Heritage 100P comes with two eyepieces, a 2x Barlow lens, and a red dot sight. The provided eyepieces are 1.25” 3-element “Super” eyepieces which are variously described as either a reverse Kellner or Konig optical configuration. While at f/4 you’re inevitably going to see some coma at the edges of the field of view at low power, the 25mm (16x) Super eyepiece is fairly sharp closer to the center of the field and has comfortable eye relief. The 10mm (40x) performs fairly well too. Both have glass optics with anti-reflection coatings, though the body and housing of each eyepiece is almost entirely plastic.
The 2x Barlow lens included with the 100P, which you insert between either eyepiece and the telescope’s focuser, yields 32x and 80x with the provided pair of 25mm and 10mm oculars respectively. It is mostly plastic, though the optics are glass. It is not very high quality but is certainly better than nothing; the alternative would be having to shop for accessories straightway as 40x is still rather low power for bright targets – 80x is about the minimum for planetary viewing that we’d recommend magnification-wise. A dedicated short focal length eyepiece or a higher-quality Barlow lens is probably a good idea to go out and purchase, due to the rather mediocre performance of the provided Barlow and in any case the 100P performs best on planets at 100-120x or so.
The red dot sight provided with the 100P is more than adequate for a small, wide-field telescope, remarkably easy to use, and is higher quality than many of the cheap red dots compared with beginner telescopes from other brands.
The Heritage 100P uses a tabletop Dobsonian mount, to which it connects via a plastic Vixen dovetail saddle. You can slide the scope in the saddle to adjust for balance with heavier eyepieces in the event you purchase any aftermarket, and to aim you simply push the telescope up and down and left to right around the sky. The mount is predominantly constructed from particle board, covered in melamine plastic laminate. The altitude (up/down) bearing deviates from the conventional Dobsonian design, in that it is technically a single-arm fork – pivoting in a small washer and ball bearing with a knob to adjust friction – but it works well. The scope swivels in azimuth (side to side) on three small PTFE (Teflon) pads around a central bolt.
The 100P also has a socket attached to the bottom with standard ¼ 20 photo tripod threads to allow for it to attach to any sturdy enough photo tripod if you wish.
Should I buy a Used Sky-Watcher Heritage 100P?
Before acquiring any second-hand Dobsonian telescope, including the Heritage 100P it is vital to thoroughly examine it for any damage to the mirror coatings or the base. At the 100P’s aperture and price range, damage to the base or mirror coatings are reasons to outright avoid purchase due to the cost of repair. A dull-looking mirror may simply require cleaning, but if there are signs of moss, chemical corrosion, pinholes, or a transparent quality to the coating, the mirror might need to be recoated. Unfortunately, this process is not cost-effective for a small telescope.
Dents on the tube of a used Dobsonian telescope are usually not a cause for concern, as they are often inevitable and typically do not impact the light path. In the event that any dents do affect the optics, they can be hammered out of the 100P’s tube fairly easily.
The Sky-Watcher Heritage 100P is of course pretty much the cheapest acceptable telescope one can find. Lower-priced 76mm f/4 tabletop scopes have flawed spherical primary mirrors and often sub-par accessories, while most tripod-mounted scopes are just completely unacceptable. The Zhumell Z100 and Orion SkyScanner 100mm, if available, are identical optically and mechanically to the Heritage 100P, albeit equipped with slightly different accessories.
- The Sky-Watcher Heritage 130P offers significantly more aperture than the Heritage 100P for bolder, brighter, and sharper views, and a collapsible tube to maximize portability.
- The Bresser Messier 5” Dobsonian has similar optics to the Heritage 130P but in a simpler solid tube. However, the provided accessories are not quite as good.
- The Zhumell Z114 features just a bit more light-gathering and resolving power than the 100P along with better quality control for its optics and easy tool-free adjustments for collimation of the primary mirror. Its fast f/4 focal ratio and resulting 450mm focal length also give it a lot wider of a maximum field of view than a 130mm f/5 tabletop scope, though it is of course a little less powerful.
- The Sky-Watcher Virtuoso GTi 150P is a highly portable telescope with a fully motorized mount featuring GoTo technology, controllable via a smartphone app or manually aimed by hand. With a 150mm (6”) aperture, it also offers more than double the light-gathering power and 50% more resolution than the 100P. The manual Heritage 150P is also a great scope if you don’t mind the loss of computerized functionality.
- The Ursa Major 8″ f/6 Dobsonian is a simple 8” Dobsonian, which boasts an impressive light gathering capacity – almost twice that of its 6″ counterparts and four times the light collecting prowess of the Heritage 100P. Despite this, its weight and bulk are only marginally greater than a 6″ f/8 Dobsonian
- The Ursa Major 6” f/8 Planetary Dobsonian, as with the 8” model, is a simple and economical option for a freestanding 6” f/8 Dobsonian. It only has a 1.25” focuser and its spring-tensioned mount is not ideal, but it works well and offers excellent performance for the price along with a fairly decent set of provided accessories.
- The Bresser Messier 6” Planetary Dobsonian is another great example of a 6” f/8 Dobsonian, with a sturdy and well-designed mount with smooth altitude bearings and sporting a 2” rack-and-pinion focuser. However, the provided accessories are fairly mediocre.
- The Bresser Messier 6″ Tabletop Dobsonian features the same optics as the Virtuoso GTi/Heritage 150P but in a solid, non-collapsible tube with a 2” rack-and-pinion focuser, atop a tabletop Dobsonian mount.
- The StellaLyra 8″ f/6 Dobsonian is a premium 8” Dobsonian, equipped with a host of additional features, including a dual-speed Crayford focuser, integrated cooling fan, and a plethora of premium accessories to help you get started. The 10″ StellaLyra model is a similarly excellent option, with minimal additional bulk but even more light collecting and resolving power.
- The Bresser Messier 8″ Dobsonian includes sharp 8″ optics, a high-quality 2.5” hybrid rack-and pinion focuser, and smooth bearings, all at a relatively affordable price point. However, the accompanying eyepiece and finder scope are of somewhat lesser quality than what is supplied with competing 8” Dobs like the StellaLyra, Sky-Watcher and Ursa Major scopes. The 10″ Bresser Messier Dobsonian shares both the strengths and weaknesses of the 8″ model.
- The Sky-Watcher Skymax 127 AZ-GTi combines the exceptional Skymax 127 Maksutov-Cassegrain optical tube with the versatile AZ-GTi mount and tripod, delivering motorized tracking and pointing capabilities that can be operated through your smartphone, or simply pushed around the sky by hand thanks to its FreedomFind encoders. The Skymax 127 Virtuoso GTi offers the same features but is mounted on the Virtuoso GTi tabletop Dobsonian mount, with the possibility to connect it to a third-party tripod. The Skymax 127 optical tube is similar in performance on deep-sky objects to the 100P apart from its narrower field of view, but significantly outclasses it for high-power planetary and lunar views.
Aftermarket Accessory Recommendations
We would highly recommend purchasing a 6mm goldline or redline (67x) wide-angle eyepiece for the Heritage 100P, which can be used with the provided Barlow (or a higher-quality replacement 2x Barlow, which is also a great item to have) for 133x magnification, about the most the 100P can handle. Alternatively or as an addition to either or both of these items, a 4mm planetary eyepiece (100x) is ideal.
A UHC/OIII nebula filter is a bit of an expensive addition to the Heritage 100P, though it can be used with other telescopes alongside the 100P in the future. It can bring out more detail and contrast in nebulae like the Orion Nebula with the 100P under light-polluted conditions, as well as objects like the wispy Veil Nebula supernova remnant under dark skies.
What can you see?
Although small, inexpensive, long-focus refractors or Maksutov-Cassegrains in the 70-80mm aperture range may perform slightly better than the Heritage 100P on the Moon and planets, the 100P’s larger aperture makes it far superior for observing deep-sky objects. It’s also of course much sturdier and more compact than typical small tripod-mounted telescopes You’ll love the Heritage 100P’s wide field of view capability. With the 100P, you’ll be able to marvel at star clusters such as the Pleiades, Hyades, Dragonfly, Double Cluster, and Sailboat Cluster, as well as many other open star clusters like M35 or the Christmas Tree Cluster, even from fairly light-polluted skies.
The Heritage 100P will also provide you with breathtaking sights of thousands of double stars, which can be split at high magnification. You’ll also be able to spot fuzzy smudges of globular clusters, and with some luck, even detect subtle details in a few of the brightest galaxies, such as dust lanes in M82 or M31, provided you have access to dark skies. And of course, the 100P will be able to show you the bright emission nebulae such as Orion (M42), the Swan (M17), and the Eagle (M16) along with a few others if you are able to get to dark skies and/or equip the scope with a UHC filter.
As for Solar System objects, the 100P is more than capable of showing you the phases of Mercury and Venus, along with thousands of razor-sharp details on the Moon like craters, mountains, ridges and cracks, along with the smooth lunar maria. Mars reveals its polar ice caps and any current dust storms; the 100P can show you a few dark markings on the planet’s surface when it is close to Earth, conditions are favorable, and preferably with a better high-magnification eyepiece than using the provided 10mm/Barlow combination. You’ll be able to easily see the moons of Jupiter, while high magnification reveals their disks and shadows when they transit in front of the gas giant. Jupiter itself shows its reddish equatorial cloud belts along with smaller atmospheric features including the famous Great Red Spot. The Heritage 100P will also be able to show you the rings of Saturn and the Cassini Division splitting the rings in two. Saturn’s dull cloud bands and a handful of its moons can also be seen with the 100P, and the scope vaguely resolves Uranus as a turquoise dot, while Neptune is hard to distinguish from nearby bluish stars of similar brightness. Neither ice giant’s moons, nor dwarf planet Pluto, can be seen with a telescope as small as the Heritage 100P, owing to their faintness.