FIRST LIGHT
Celestron StarSense Explorer 8-inch Dobsonian
Smartphone targeting and big aperture impress on this enjoyable ‘Push-To’ light bucket
VITAL STATS
• Price £649
• Optics 203mm (8-inch) Newtonian reflector
• Focal length 1,200mm, f/5.9
• Mount Altazimuth Dobsonian
• App control StarSense Explorer
• Extras Smartphone dock, 2-inch Crayford focuser, 25mm eyepiece, red dot finder, eyepiece rack, collimation cap, Starry Night Basic Edition
• Weight 9.3kg tube, 10.3kg base
• Supplier Celestron
• Tel 0118 467 1200
• www.celestron.com
Celestron’s StarSense technology has been around for a few years, but only on small telescopes aimed at beginners. It uses an app on your smartphone to find targets in the night sky, and this is the first time the StarSense smartphone holder has featured on an 8-inch aperture Newtonian reflector and Dobsonian mount. There is also a 10-inch model available.
StarSense on a Dobsonian is a revelation and is not to be confused with computerised ‘Go-To’ telescopes that automatically slew to objects at the touch of a button. StarSense is a manual ‘Push-To’ system that merely shows on a smartphone screen where to point the telescope, a bit like satnav does for drivers. The Celestron StarSense Explorer 8-inch Dobsonian isn’t just easy to use, but is capable of giving first-timers an addictively impressive view of deep-sky and Solar System objects alike.
It is mounted on a manual altaz base that lacks any kind of motor, so the only astrophotography possible is afocal through the eyepiece, usually of the Moon. The base comes flat-packed and takes about 20 minutes to construct. The tube is best left in situ, merely turned vertically when in storage, but moving it outside is most easily done by separating tube from mount. That is fairly simple to do and both the mount and the tube have grab handles.
Stellar satnav
The base has a built-in eyepiece rack for the supplied 1.25-inch Celestron Omni Plössl eyepiece, whose 25mm focal length offers up to 48x magnification. Two slightly confusing inclusions are a red dot finder and free access to Celestron’s Starry Night Basic Edition planetarium software for desktop computers. The former is handy for quick manual targeting, despite the presence of StarSense, but since it is placed on the opposite side of the telescope tube to the eyepiece it is very difficult to use. Meanwhile, the software is surely surpassed by the StarSense app and seems to be a hangover from previous products.
StarSense is highly impressive, but it is not perfect. As with all guided telescopes, this one needs to have its optics aligned with the night sky, but here what’s important is the smartphone’s view of a reflection of the stars above. As the smartphone sits in its holder, its camera is positioned over a mirror and reveals its view on screen. The trick is to match this with the position of a star in the telescope’s eyepiece. The final act is to pinch-to-zoom on the smartphone screen to get that same star in its virtual crosshairs. Doing so requires a very bright star and a little confidence, though it’s also possible to do all this in daylight with a distant chimney pot or a streetlight. During use, StarSense frequently realigns itself, mostly after the telescope has been pushed correctly towards its target, at which point the software does more plate-solving to refine its position and guide you in with exacting precision. It is impressive, but a partly cloudy sky can give it problems. Happily, the app has a red light mode.
Considering its size, this telescope is surprisingly lightweight to use and easy to manipulate. Build quality is good and the Dobsonian base is stable; the bearings are just smooth enough. The tension can be tweaked on the altitude axis and it is possible to make very slight movements and, crucially, brake quickly. It is then easy enough to nudge the tube’s panning knob to keep the target in the field of view.
Dobsonians are nicknamed ‘light buckets’ and this one lives up to that name. Cue sharp, bright, inverted views of the Andromeda Galaxy, M31, and the Great Globular in Hercules, M13, from a light-polluted location. Stars have four diffraction spikes, but they’re lessened by XLT reflective coatings. Splitting double stars proved short work, with the constituent stars of the Epsilon Lyrae ‘Double Double’ star easily resolved. The rings of Saturn and cloud bands on Jupiter are also visible, though it does its best work on the deep sky. All in all, it is a hugely enjoyable telescope to use and will delight beginners and more experienced observers alike.
StarSense Explorer app
Celestron’s StarSense Explorer app, available for Android and Apple smartphones, has been refreshed and expanded for the debut of this Dobsonian. Since this telescope’s limiting magnitude is +14.2, it can glimpse targets much fainter than any of the small reflectors and refractors elsewhere in the StarSense Explorer range. Essentially a customised version of the SkySafari Plus app, StarSense Explorer has now been extended beyond the Messier objects, bright stars, the Moon and planets to include NGC, IC and many other catalogues of deep-sky objects.
You can find almost any target you want, though exploring beyond the curated ‘tonight’s best’ list requires a manual search of its database. It’s worth attaching wireless Bluetooth headphones to your smartphone, because the app includes audio commentary for hundreds of objects in its database. As well as being informative, it may encourage you to linger a little longer on objects.
KIT TO ADD
1. Portable battery for smartphone
2. 2m cable to attach a smartphone battery
3. Bluetooth earphones to hear in-app audio
VERDICT
