The Optical Tube
The Sky-Watcher Explorer 200PDS optical tube assembly is an 8-inch (200mm) f/5 Newtonian reflector with a 1000mm focal length. In line with standard imaging Newtonian telescopes, the optics in the Explorer 200PDS are of fairly high quality. With its f/5 focal ratio, coma is barely noticeable at the edge of the visual field when using a 1.25-inch eyepiece. However, cheaper wide-angle eyepieces such as the included 28mm 2″ LET eyepiece may exhibit other aberrations at lower magnifications, particularly away from the field’s center.
Equipped with a relatively straightforward 2-inch, dual-speed Crayford focuser, the 200PDS lacks a compression ring to secure 2” accessories, such as the provided 2” LET eyepiece or the included 1.25″ adapter. Consequently, it might be prone to some slippage or sag under heavy loads like a large camera, filter wheel, and coma corrector. However, for lighter payloads like a DSLR or a simple color camera, this is only a minor concern. The focuser exhibits smooth movements and can accommodate an add-on motor focuser unit, such as the ZWO EAF.
Collimation is of paramount importance with any f/5 telescope, especially those primarily used for astrophotography. The Explorer 200PDS’s collimation is adjustable via three spring-loaded knobs located at the rear of the primary mirror (secured further by an additional set of locking screws). Adjusting the secondary mirror, however, requires a hex key. Our comprehensive collimation guide may be useful for understanding this process. This telescope generally retains its collimation well, but replacing the primary mirror cell’s standard springs with more robust alternatives can enhance the telescope’s stability over time and during movement across the sky. A 12V DC-powered 80mm fan, situated at the rear of the primary mirror cell, assists in quickly equilibrating the primary mirror to ambient temperature.
The Sky-Watcher Explorer 200PDS comes equipped with standard tube rings and a Vixen-style dovetail bar, facilitating attachment to any astronomical mount, including the provided HEQ5 Pro. If desired, this bar can be replaced with a Losmandy-style one, but this would necessitate upgrading the HEQ5 Pro’s saddle to match. For increased stability and the option to mount additional accessories such as a guide scope, a second dovetail bar attached to the top of the rings is recommended.
Accompanying the Explorer 200PDS, you’ll find a single eyepiece – a 2″, 28mm focal length Sky-Watcher L.E.T. ocular. This three-element eyepiece is equipped with a convenient twist-up rubber eyecup for optimal comfort. With the 200PDS, this eyepiece provides a magnification of 36x. Its apparent field of view is approximately 60 degrees, which translates into a true field slightly in excess of 1.5 degrees, equivalent to about 3 times the angular diameter of the full moon, when employed with the 200PDS. This is enough for viewing even the largest deep-sky objects.
However, under heavily light-polluted skies, the 36x provided by the 28mm LET may constitute too low a power for the 200PDS and might result in a rather washed-out, grey-brown background sky. Consequently, for deep-sky viewing with the 200PDS, an eyepiece within the 16-22mm focal length range might be more suitable. Higher magnification eyepieces would also be advisable for observations of the moon, planets, and double stars.
Due to the simple 3-element optical design of the L.E.T eyepiece, it also falls short in its correction for edge-of-field astigmatism when combined with the fast f/5 focal ratio of the 200PDS. This combined with the scope’s inherent coma at f/5 means that half the field will be populated by blurry stars.
Sky-Watcher also includes their standard 9×50 finder scope with this model. It is conveniently attached with a Synta/Vixen-style shoe, facilitating easy interchangeability with other finders, such as a red dot unit. The 9×50 finder scope allows the observation of stars several magnitudes fainter than what the naked eye could perceive, as well as the brightest of deep-sky objects like star clusters. This is all visible within an upside-down field of view spanning roughly 5 degrees, delineated by non-illuminated crosshairs. The finder scope functions admirably for the task of aligning the HEQ5 Pro mount with the celestial sphere.
The NEQ6 Pro Mount
The Sky-Watcher NEQ6 Pro is a high-quality mount offered by Sky-Watcher for visual and astrophotography use,
Boasting a declared weight capacity of 18 kg, the NEQ6 Pro proves its prowess by easily accommodating either an 11″ or 12″ Schmidt-Cassegrain or Ritchey-Chretien, a 10″ Newtonian, or even the most sizeable refractors and Maksutovs for visual observation where the necessity for precise long-exposure tracking is not of paramount concern.
In the realm of long-exposure deep-sky astrophotography, it is generally advised to halve, or perhaps generously apply two-thirds of, the stated weight capacity. This means you would be looking at a load capacity of around 20-27 lbs. These calculations mean the NEQ6 can comfortably accommodate an 8″ Newtonian like the 200PDS for imaging. Be mindful, however, that larger telescopes including the 200PDS may encounter challenges in achieving the requisite tracking or guiding accuracy, or maintaining stability in windy conditions, especially during longer exposures.
For visual astronomy pursuits, operating the NEQ6 Pro is a rather straightforward affair. Once the mount is fully assembled, the setup process is only marginally more complex than that of an alt-azimuth mount. The only additional steps required are the balancing of the equipment and polar alignment. In the case of solar, lunar, and planetary imaging, the procedure remains largely the same, although it is recommended to utilise an eyepiece to initially align and centre your object of interest before switching to a camera.
Following the sequence of setting up and levelling the tripod, polar aligning the mount, balancing the telescope, and powering up, the NEQ6 Pro’s SynScan system prompts you to carry out a GoTo alignment. This task is as easy as it is with any other GoTo mount, with the only requirement being to centre your telescope on two or three bright stars, thus completing the alignment. The system also offers handy quick setup functions such as one-star or Solar System Align, although these might deliver less accuracy. With an extensive database of over 40,000 celestial objects, the SynScan hand controller features functions like “Sky Tour” and the capability to input new objects like comets. Regular syncing of the controller will serve to rectify any tracking errors that might occur due to imperfect polar alignment or balance, and you also have the option to adjust the slew speed for minor corrections when centre-aligning an object at high magnification or with a camera.
When you’re prepared to embark on capturing long exposure photography, you have the option to utilise software to target the telescope and plate solve until your target is accurately located, bypassing the SynScan controller. Image capture software can also manage motor focusers or filter wheels and handle meridian flips automatically. This capability saves you valuable time and eliminates potential frustration.
The implementation of autoguiding is achievable with PHD2 and a compatible guide scope and camera, which can typically be automatically controlled by the same software suite running your mount. If everything is aligned and focused correctly, and the software operates without any hitches, you can comfortably leave your telescope, mount, and computer to operate autonomously.
Should I buy a Used Sky-Watcher Explorer 200PDS NEQ6 Pro?
Choosing to invest in a pre-loved Explorer 200PDS/NEQ6 Pro could indeed present a savvy option, with the potential savings made on the initial outlay possibly substantial enough to accommodate the purchase of a guiding setup and coma corrector.
Before giving the green light on your purchase, it’s absolutely critical to ascertain that the NEQ6 Pro mount is in proper working order. It should power up, slew, and track as expected and show no significant indications of corrosion. Equally, the optics nestled within the Explorer 200PDS optical tube should be devoid of any telltale signs of corrosion or damage to the mirror coatings. The cost to re-coat could rapidly eclipse the price tag of a new optical tube assembly. Should there be missing accessories or counterweights, fear not, as these can be replaced quite affordably and with relative ease, as could a lost SynScan hand controller. Sky-Watcher supplies components like adjustment/saddle knobs or the counterweight shaft as spares for the NEQ6, and ADM provides upgraded alternatives.
For those of you who have a particular interest in deep-sky astrophotography, our articles on the Best Equatorial Mounts and Best Optical Tubes might be of considerable value. These guides aim to assist you in the process of selecting an optical tube and mount combination that best fits your personal preferences, constraints of budget, specific camera features, and the celestial objects you’re most enthusiastic about imaging. To facilitate your decision, we’ve put together a selection of telescopes that are highly recommended for visual observation, and potentially, light astrophotography.
Under 1200 Range
- The StellaLyra 10″ f/5 Dobsonian provides remarkably superior resolution and light-gathering prowess compared to an 8” scope with the likes of the 200PDS. Despite its large aperture, it retains a high level of portability and comes loaded with an impressive array of features and accessories. The StellaLyra 8” f/6 model, while sporting the same quality attributes and accessories, is a more economical choice and essentially shares the same physical dimensions as the larger 10″ StellaLyra model.
- The Celestron StarSense Explorer 10″ Dobsonian presents not just a 10″ aperture, but also introduces a level of computerised pointing functionality without motorised tracking, owing to the cutting-edge StarSense Explorer technology it incorporates. This telescope is thoughtfully designed with various knobs, handles, and cutouts, which significantly simplify its transportation. The StarSense Explorer series also includes an 8″ model that delivers a comparable top-tier experience.
- The Sky-Watcher Virtuoso GTi 150P possesses a 6″ aperture and is equipped with a collapsible tube for maximum portability. The telescope’s GoTo tabletop Dobsonian mount is designed for manual adjustment, which doesn’t interfere with its tracking or pointing accuracy. The automatic pointing of the mount is cleverly controlled via a user’s smartphone or tablet. Its manual counterpart, the Heritage 150P, offers the same features and specifications, the key difference being the absence of electronic components.
Over 1200 Range
- The Celestron NexStar Evolution 8, although quite compact compared to the monster 200PDS and NEQ6, matches it in light-gathering and resolution power. The NexStar Evolution mount is equipped with fully automated GoTo and tracking capabilities, an integrated lithium battery, and a WiFi adapter, offering the convenience of managing the telescope via a smartphone or tablet. Although deep-sky astrophotography is possible with this scope in its stock configuration or atop an equatorial wedge, better results can be achieved when the C8 XLT optical tube is mounted on a beefy equatorial mount like the NEQ6.
- Sky-Watcher Skyliner 250P FlexTube GoTo Dobsonian boasts a fully automated GoTo and tracking system featuring Sky-Watcher’s unique FreedomFind encoders for smooth manual operation. This design innovation allows for manual telescope aiming, even when powered on. Thanks to the motorised tracking, it’s possible to perform planetary imaging with this telescope whilst also relishing in the excellent views provided at the eyepiece.
Aftermarket Accessory Recommendations
If your ambitions lean towards visual observation with your Explorer 200PDS, it is absolutely paramount that you consider enhancing your eyepiece collection. Eyepieces offering greater magnification power, and thus with shorter focal lengths than the supplied 28mm LET, become crucial for observing phenomena such as the Moon, planets, more compact deep-sky objects, and double stars. A 16mm UWA (yielding a magnification of 63x) offers an ideal balance for medium-power viewing of deep-sky objects and the ability to observe the full moon in a single view. For numerous evenings of planetary viewing, even under less than perfect seeing conditions, a 10mm UWA (providing a magnification of 100x), or a 9mm ‘redline’ or ‘goldline’ (achieving a magnification of 111x) deliver the optimal magnification. This is also perfect for taking in the majesty of globular clusters. The Explorer 200PDS is well equipped to manage magnifications of up to around 375x, so employing a 2x or 3x Barlow lens or an eyepiece with a particularly short focal length in the range of 3-5mm can help reach these dizzying heights of magnification.
As an owner of the Explorer 200PDS, it would be highly beneficial to have a Cheshire collimation tool at your beck and call. This useful piece of kit will aid you in maintaining accurate collimation, assuring you of pinpoint sharp stars across the field when used in conjunction with a coma corrector, and equally sharp views at the eyepiece.
When it comes to enhancing contrast on nebulae through any telescope at the eyepiece, a UHC nebula filter is an indispensable ally. This filter unveils previously hidden details or completely new celestial bodies from the abyss, even under skies polluted with light. However, for the optimal viewing experience, a dark sky is still the gold standard, both with and without a filter.
Due to the fast f/5 focal ratio of the Explorer 200PDS, it would be worth considering the addition of a coma corrector to your equipment arsenal, whether your preference lies in viewing or imaging. The Baader MPCC stands as a suitable choice for both visual use at low magnifications and imaging. It affixes directly to your eyepiece or camera. The Explore Scientific HRCC and Tele-Vue Paracorr II serve as worthy, albeit slightly more costly, alternatives.
For long-exposure imaging with the Explorer 200PDS, a motor focuser such as the ZWO EAF is an ideal companion. It facilitates finer focus adjustments when used with an appropriate Bahtinov mask. A 50-60mm guide scope and a fitting guide camera are recommended for piggybacking on top of the Explorer 200PDS. Furthermore, a T-adapter for connecting the scope to a DSLR or mirrorless camera and a corresponding T-ring are essential. You will also need some kind of DC power supply, like the Celestron PowerTank Lithium, to power the HEQ5 Pro mount, unless you are conveniently positioned near a mains power outlet.
What can you see?
Operating the Explorer 200PDS, coupled with the NEQ6 Pro mount or any other German equatorial mount, for visual purposes can present its own unique set of complexities. You may frequently encounter scenarios wherein the orientation of the eyepiece positions you in an inconvenient or impossible to reach pose, thus calling for a rotation of the tube within its rings to attain a more comfortable viewing angle. However, this seemingly mundane task could potentially upset the balance and alignment of the HEQ5 Pro mount. One possible workaround to this could involve utilising a pair of homemade Wilcox rotating rings, but even with this modification in place, it may still fall short of entirely resolving the issue and replicating the effortless ergonomics of a Dobsonian telescope. This characteristic is an innate part of the user experience when dealing with equatorially mounted Newtonians, and its effect is exacerbated as the size of the telescope scales up.
Equipped with a 2” wide-angle eyepiece, the Explorer 200PDS can lay claim to a wide field of view that marginally surpasses that of a typical 8” f/6 Dobsonian. This endows it with particular prowess when observing expansive open star clusters such as the Double Cluster, the Wild Ducks Cluster (M11), and Pleiades (M45). These clusters can be effectively observed under almost all circumstances, and you might notice that many of the stars within these clusters stand out due to their remarkable colouration. Moreover, this telescope is capable of distinguishing individual stars within an array of globular clusters, encompassing nearly all the clusters featured in the Messier catalogue, among others. For optimal observation of these globular clusters, it’s advisable to employ magnifications of 80x or above and to observe under the canvas of a dark sky.
When faced with conditions of moderate light pollution, the Explorer 200PDS proves capable of unveiling the intricate nuances within bright nebulae, inclusive of M42 and M8. Nonetheless, for an optimal viewing experience, it is highly recommended to observe these celestial wonders under darker skies and/or through a top-tier UHC nebula filter. Given the provision of suitably dark skies and a UHC filter, it becomes feasible to observe fainter nebulae such as the Veil and North America Nebula, too. The substantial 8″ aperture of the Explorer 200PDS further enables you to discern fine details and a striking palette of azure, turquoise, and emerald hues in planetary nebulae like the Blue Snowball, the Ghost of Jupiter, and the Cat’s Eye.
Any 8” telescope, the Explorer 200PDS being no exception, facilitates the observation of intricate details within galaxies under dark skies. However, the scourge of light pollution frequently robs you of these finer details. Galaxies such as Andromeda (M31), M82, M64, M65, and M101 can reveal dust lanes, while in galaxies like M51, M33, and M101, you might spot hints of spiral arms. It is also feasible to observe numerous galaxy groupings and clusters, such as those located in Virgo, Leo, and Coma Berenices.
When compared with a typical 8” f/6 Dobsonian, the Explorer 200PDS may slightly fall short when it comes to planetary viewing. This is primarily due to the shallower depth of field at f/5, in comparison to f/6, which makes focusing at higher magnifications slightly more challenging. The requirement for accurate collimation takes on greater importance, and to reach comparable magnification, eyepieces with shorter focal lengths become necessary. However, satisfactory views of the planets and the Moon are still within reach. You can anticipate seeing a wealth of detail on the Moon, the phases of Mercury
If one were to draw comparisons between the Explorer 200PDS and a standard 8” f/6 Dobsonian, one might note that the former may not match the latter in terms of planetary observation. This can be primarily attributed to the relatively shallow depth of field offered by the f/5 of the Explorer 200PDS, in contrast to the f/6 of a typical Dobsonian. As a result, focusing becomes a touch more arduous at higher magnifications. The demand for precise collimation is accentuated, and achieving similar magnification levels calls for the use of eyepieces with reduced focal lengths. Despite these factors, it’s worth noting that the Explorer 200PDS is still capable of delivering satisfactory views of the celestial bodies in our solar system, including the planets and the Moon.
Under favourable observing conditions, you can look forward to a plethora of lunar detail on the Moon’s surface. The phases of both Mercury and Venus are clearly visible, and you can also spot a few dark markings on Mars, accompanied by its polar ice caps.
When graced with clear skies, the Explorer 200PDS allows for a spectacular show put on by Jupiter. You can witness a vibrant array of cloud belts and storms across Jupiter’s surface, the most notable of which is the Great Red Spot. Furthermore, the moons of Jupiter present themselves as well-defined disks and are often accompanied by their individual shadows during transits. Saturn, too, puts on an equally intriguing display with its discernible cloud bands, the distinct Cassini Division within its rings, and a number of its moons.
Uranus, when observed through the Explorer 200PDS under a dark sky, emerges as a somewhat fuzzy teal disk with a handful of its moons faintly visible to the observant viewer. Neptune often proves a challenge to distinguish from a star, yet its moon, Triton, usually stands out quite noticeably. However, the observation of Pluto necessitates a larger aperture, typically between 10-12”, and clear, dark skies. Even then, Pluto merely appears as a star-like point.
The Explorer 200PDS optical tube is sturdily mounted atop the NEQ6 Pro mount, though at 1000mm focal length you’ll need autoguiding for exposures of any appreciable length and you’ll be sure you have accurate collimation for sharp stars across the field. Accurate polar alignment and precise balancing of the telescope on its mount are also crucial. At f/5, a coma corrector and motor focuser might also be worth purchasing to make imaging a less frustrating and time-consuming experience.
The Explorer 200PDS also offers a rich vein of potential for those keen on delving into planetary astrophotography. To achieve an image scale sufficiently large for detailed observation, you’d need to utilise a 4-5x Barlow lens. However, sourcing a high-quality Barlow lens of this specific type might prove a bit tricky, unlike the more readily available 2-3x Barlow lens typically ample for an f/10 Schmidt-Cassegrain telescope.
Nonetheless, the 200PDS does not disappoint when it comes to snapping superb shots of lunar surface details, as well as capturing sunspots when used in conjunction with a solar filter. Additionally, it’s more than capable of securing images of the phases of Venus and Mercury, surface features and dust storms on Mars, atmospheric details on Jupiter and Saturn as well as the disks of their larger moons. You might even tease out subtle nuances of atmospheric detail on Uranus. For the adventurous ones amongst us, who are open to playing around with longer exposures or heightened gain settings, the ability to capture images of the elusive moons of Mars, Uranus, and Neptune could become an achievable reality.