Celestron CGE Pro 1100 HD review

All too often in today’s marketing-driven world, we see the word ‘Pro’ added to equipment where it really doesn’t belong.

But in this case, the word has true meaning.

The three huge boxes that contain this telescope are an indication that this setup is something special and, once assembled, it wouldn’t look out of place in a professional observatory.

Although you can assemble it yourself, it is reallya two-person task, such is the weight of the various components.

The CGE Pro mount is an imposing and impressive piece of engineering, sitting on topof a heavy-duty tripod.

This has 7cm-diameter stainless steel legs, making it a very steady platform for the ivory and orange 11-inch Schmidt-Cassegrain telescope (SCT).

The build quality and attention to detail is of the highest order: we were particularly impressed by touches like a locking power supply lead and the four clutch-locks on each axis.

The mount allows you to track up to 20° past the celestial meridian, which would allow nearly 1 hour 20 minutes of extra imaging before having to do a ‘meridian flip’.

This is the process of switching the scope from one side of the mount to the other to continue tracking an object as it passes though the meridian – a task abhorred by astro imagers!

The NexStar hand controller has many excellent functions, the most innovative being the All-Star polar alignment, which makes polar alignment a quick procedure and explains the lack of a polarscope in the mount itself.

We also liked the ability to reverse the direction keys to match the movement of the view through the eyepiece.

Celestron’s 11-inch SCT needs no introduction (we last saw it in July 2009’s First light), but this example, with an EdgeHD optical design, takesthe tube to a new level, correcting the common aberrations found in SCTs such as off-axis starcoma, when stars are misshapen.

There are also effective mirror locks to hold the mirror in placeonce focused, and vents on the rear to decreasethe cool-down time substantially.

The optics have enhanced multi-layer StarBright XLT coatings to cut down on internal reflectionsand the telescope is Fastar-compatible too, which means that the secondary mirror can be removed and replaced with an optional HyperStar unit to convert the telescope into a wide-field f/2 astrograph for imaging.

With these great features, there is plenty to appeal to both visual astronomers and astrophotographers.

When clear, dark skies finally arrived, the Go-To system worked accurately, especially after we had synchronised the mount on two or three extra objects.

High-speed slewing was quite noisy, but finer adjustments using the hand controller were supremely smooth and backlash-free.

In a new light

Using the supplied 23mm eyepiece, we enjoyed some superb sights through the EdgeHD, including the best view of the Orion Nebula we have ever seen – it was absolutely spectacular.

M82, the Cigar Galaxy, was a wonderful sight with clear mottling and hints of its violent past, while its neighbour M81, Bode’s Galaxy, showed excellent detail.

Saturn and five of her moons – a sixth by averted vision – were particularly crisp and clear, and we were impressed with the good star shapes we observed right out to over 95 per cent of the field of view.

The waxing gibbous Moon had wonderfuldetail along its short terminator.

The only drawback was the straight-through finder; a right-angle version would have been much more usable.

Because of the corrective optics, the scope needs a special T-adaptor for imaging to ensure that the correct spacing of the sensor is achieved.

The adaptor arrived during a period of heavy cloud cover so we were unable to take any images, but based on the views through the eyepiece, we’d expect great things from this scope.

We very much enjoyed using the CGE Pro 1100 HD and although it’s a huge investment at nearly £9,000, its excellent engineering and innovative features mean we would recommend it to anyone considering a serious upgrade.

Optics with an edge

Conventional Schmidt-Cassegrain scopes have a corrector plate at the front to help correct spherical aberrations.

These result in off-axis light (light collected away from the centre of the mirror) being slightly out of focus.

However, the conventional corrector plate doesn’t correct the other error typically found in an SCT – coma, which manifests itself as comet-shaped stars towards the edge of the field of view.

These misshapen stars become very obvious in deep-sky images, where they can spoil the appearance of an otherwise good photo.

The special optics in this EdgeHD version of the SCT incorporate a new ‘aplanatic’ Schmidt telescope design, which includes a coma corrector and field flattener housed within the baffle tube assembly at the rear of the scope, plus a small change to the curvature of the secondary mirror.

This optical system corrects both coma and spherical aberration, resulting in sharp stars even at the very edge of the field of view.

Eyepiece and star diagonal

The telescope is supplied with a 2-inch star diagonal and a very high quality 2-inch fit 23mm Axiom LX eyepiece, giving a magnification of 122x. This fully multicoated ocular has an 82° apparent field of view, twist-up rubber eyecup and a rubber grip ring for safe handling even with cold hands.

Mirror locks

A Schmidt-Cassegrain telescope is focused by moving the primary mirror backwards and forwards with a focus knob on the rear of the scope. However, this freedom of movement can cause ‘mirror flop’, where the mirror moves slightly when pointing at different parts of the sky. The mirror locks stop this from happening.

Hand controller

The proven NexStar hand controller comes with a comprehensive 40,000+ object database covering the Messier, Caldwell, NGC, IC, Abell Galaxies, Solar System objects and selected SAO star catalogues. It also has a socket allowing full computer control of the mount with the supplied NexRemote software and cable.

All-Star polar alignment

Simply align your mount to roughly point north (you don’t even need to be able to see Polaris), align on three stars and the mount moves to where the third star would have been if the mount had been accurately polar aligned. Adjusting the altitude and azimuth axes to centre the third star results in perfect polar alignment.

This review originally appeared in the June 2010 issue of BBC Sky at Night Magazine.