Focal Length: 1,200mm; f/4.7
Eyepieces: 28mm (2-inch fit), 12.5mm (1.25-inch fit)
Mount: Motorised Dobsonian
Supplier: The Widescreen Centre
From humble beginnings, John Dobson’s telescope design has come a long way.
His original was simply a ‘light bucket’ with a large mirror, mounted on a rocker box and turntable.
It gave detailed views of the night sky that began to approach what can be achieved with astrophotography, but at the expense of not being able to track the sky.
How things have changed.
With the introduction of Go-To technology, 21st century auto-tracking is at last possible with a ‘Dob’, Orion’s SkyQuest XT10g.
The XT10g is a 10-inch f/4.7 telescope in two sections; the tube assembly and the rocker base.
The tube is ready to drop onto the rocker base once the finder’s attached, while the rocker base comes with base plates and motors installed.
Only the sides and eyepiece tray need to be fitted on.
It’s definitely a step in the right direction to have the base’s motors, circuit boards and encoders ready assembled.
It means the delivery box may be a little bigger than you expect, but it’s worth it for the peace of mind that comes from knowing you haven’t damaged a circuit board during assembly.
Once it’s all been set up, the motors mean you don’t have to push this Dobsonian manually, and unevenly, round the sky.
The Go-To makes tracking easy and even.
Also in the package is a 28mm DeepView 2-inch-fit eyepiece giving 43x magnification, and a 12.5mm illuminated crosshair Plössl eyepiece to use when aligning the Go-To system.
This gives non-illuminated views at 96x with the crosshairs turned off.
There’s a dual-speed Crayford focuser that accepts either 1.25- or 2-inch-fit eyepieces, a red-dot finder, a collimating cap and an eyepiece tray for the base.
The whole system is quick to set up in the field and pretty portable – it fits on the back seat of a car. The only extra you need is a 12V DC power supply.
Using the 28mm eyepiece on Altair – our test star – it was good to see that the inner 75 per cent of the view was nice and sharp.
We then used the 12.5mm eyepiece on several doubles, including Albireo and as a test for higher resolution,
Epsilon Lyrae, the Double Double. Albireo was gorgeous with gold and blue stars, while Epsilon Lyrae was clearly split into all four stars with the higher magnification eyepiece.
Next we turned to Jupiter and were well rewarded with subtle detail along the northern equatorial belt.
The planet’s southern equatorial belt was still absent, so the Great Red Spot stood out a treat.
A tour of deep-sky objects beckoned.
This was when we tested the XT10g’s slew rate, starting low in the east with the Pleiades and timing how long it took the scope to motor over to the Ring Nebula in Lyra, higher in the west.
On average, it took an impressive 56 seconds.
Then we moved on to galaxies, including NGC 7331 in Pegasus – a nice, elongated smudge – with three members of the Stephan’s Quintet group of galaxies sitting nearby in the view.
We got the fourth with averted vision. M13, the Great Globular in Hercules, was impressive and the Dumbbell Nebula, M27, was a lovely misshapen disc.
Nebulae like the Omega Nebula (M17) were detailed, while star clusters such as the Wild Duck Cluster (M11), were rich and sparkling.
Old favourites like the Pleiades (M45) and the Double Cluster further enhanced our impression of this Dob.
The views were certainly worthy of photographing for posterity.
But even though the base has the ability to track the sky, this is an altaz mount, so the view would rotate and introduce trailing during the long exposures needed to image deep-sky targets.
However, some imaging programs do have de-rotate routines, and short exposures on bright subjects like the Moon would be no problem.
Overall, we thoroughly enjoyed our time with the XT10g.
It was reasonably light and portable for its size, while the Go-To accuracy and tracking were impressive.
With this new chapter in the life of the Dobsonian, Orion has set the bar high.
It will be interesting to see how other Go-To Dobs like the Sky-Watcher Skyliner-200P FlexTube SynScan Go-To compare.
The SynScan hand controller was quite easy to set up with just the normal basic details of your latitude and longitude, date and time, and as long as the base is level then the alignment is quite straightforward.
Using the 12.5mm illuminated eyepiece and two-star alignment, we had successfully completed the alignment procedure within minutes.
After this we were able to slew accurately to anything in the database of 42,000 objects.
The Go-To placed each object within the inner 25 per cent of the view of the 28mm DeepView eyepiece every time.
We were also impressed when we left the telescope tracking on M27 and came back to it after 30 minutes to find it still in the view of the higher power eyepiece without any significant amount of drift.
If we have any criticism then it would only be the noise from the altitude motor when the system is slewing from target to target, but otherwise the actual tracking was relatively quiet.
Overall, Go-To and tracking did their job well, making short work of finding and following objects to provide a very enjoyable experience at the eyepiece.
A 10-inch mirror collects 56 per cent more light than an 8-inch mirror, but if the optical surfaces are poorly figured or out of alignment then that extra light could be wasted. We found there were no apparent defects in the primary or secondary mirror and that we could quickly re-collimate the telescope if needed with the large knobs at the base.
Getting a perfect focus is essential for seeing detail on planets and in deep-sky objects.
We were able to pick out subtle features on Jupiter with fine adjustments to the dual-speed Crayford focuser.
It was well placed, even when the scope pointed at the zenith, was smooth to use and didn’t have too much slack.
The SynScan hand controller was easy to set up and use.
The red glow of the buttons and display weren’t distracting or damaging to night vision and the menus were easy to navigate.
We selected a wide range of objects from the 42,000-object database and were taken to them accurately with the Go-To.
The XT10g’s mount provided a good, firm base for the telescope with little play in either of the axes.
It was highly portable and could easily fit on the back seat of our car.
The altitude motor was a little noisy slewing, but tracking was smooth and quiet.
The red-dot finder gave a bright red spot for initially finding objects. It is positioned near to the focuser, but we found we could get to it easily whatever position the tube was in.
Once aligned with the main optical axis, the finder remained aligned throughout our observing session.
This review originally appeared in the December 2010 issue of BBC Sky at Night Magazine.