Orion SkyQuest XX16g Dobsonian
Aperture: 406mm, 16 inches
Focal Length: f/4.4
Eyepieces: 28mm eyepiece, 12.5mm illuminated reticule eyepiece
Finderscope: Zero-power EZ finder
Mount: Go-To mount
Supplier: The Widescreen Centre
Telephone: 020 7935 2580
Large aperture Dobsonian telescopes are ideal if you want spectacular deep-sky views.
But what if you also want Go-To ability and a scope that fits easily in your car so you can travel with it to darker skies?
If you want all of those things, then Orion’s new SkyQuest XX16g could be for you.
The telescope has a 16-inch primary mirror with enhanced reflectivity coatings, as well as full Go-To capability and motorised tracking.
But it can also be broken down into separate parts that will fit in an average car, allowing you to take it away from the city lights and make the most of that big aperture.
The owner’s manual is nicely detailed.
Photos showed exactly what is packed in each box and give comprehensive step-by-step assembly and operating instructions.
Putting it together is a straightforward process, although the manual shows the differently designed cell for the smaller XX12g.
Disassembling it into manageable parts to take outside or load into a car takes 5-10 minutes, while reassembly takes 20-25 minutes.
The ground board is quite bulky, and slightly larger and heavier than perhaps it could have been.
A fair amount of the assembly time was spent attaching the nine 1kg counterweights, which help balance the head unit that houses the secondary mirror.
A lighter, less overly robust head would have eliminated this task and saved further weight.
Minor collimation adjustment of the main mirror is always needed before observing – it’s a relatively painless procedure and fully explained in the manual.
Setting up the Go-To requires a two-star alignment process.
This involves manually centring a bright star in the supplied illuminated crosswire eyepiece, automatically slewing to the second and then using the motor control buttons to centre this second star.
We found the whole Go-To system to be well-behaved and relatively simple to use.
You can use the motors to automatically move to new objects or you can release the friction clutches and push it most of the way before finishing off with the motorised Go-To.
If you do decide to push it, the closed-loop control means you won’t lose alignment when you unlock the bearing clutches.
Whichever method you use, the accuracy seems to be the same and when you have found the target, wherever you’re pointing in the sky, the motors automatically continue to follow it.
There’s no need for constant nudging and you can use the handset buttons to move the scope smoothly in any direction if you wander off target.
Automatic tracking also enables you to have a go at planetary imaging using a video camera attached to the focuser.
Astrophotography of brighter deep-sky objects may even be possible by stacking short exposures.
On a night of good seeing, we found the optics of the scope gave us well-contrasted views of Jupiter and the Moon.
And, of course, the sizeable aperture gave great views of deep-sky objects, including the Orion Nebula with its bat-like wings and the sweeping chains of stars of open cluster M35.
The Go-To made viewing the centre of the Virgo Cluster a pleasure rather than a chore and then drove us on a short distance to view the faint but wonderful razor of edge-on galaxy NGC 4762.
Star testing showed some minor differences either side of focus – possibly arising from uneven cooling of the mirror, which is substantially thicker at the centre than at the edges.
The optional elasticated shroud helps keep thermal currents from an observer’s body out of the light path and noticeably improved images, but didn’t stop the secondary from dewing up after about two and a half hours.
A lightweight extendable dew shield would help here.
Overall, the XX16g’s innovative design features enhance the appeal of owning a large Dobsonian and we expect to see several at this year’s UK star parties.
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This review appeared in the June 2013 issue of BBC Sky at Night Magazine