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In amateur astronomy, if nowhere else, size matters. The larger a telescope is, the more detail it can detect, and the brighter an object will appear in the eyepiece. Amateur telescopes range from less than three inches in diameter up to a whopping fourteen inch diameter, with an exponential increase in price.
With increasing telescope diameter comes increased length. For telescopes larger than ten inches or so, the Schmitt Cassegrain type offers the best portability due to its compact shape. For my latest telescope, I decided on the Celestron CPC 1100. As the name suggests, this telescope has a primary mirror diameter of eleven inches.
This scope is at the larger end of the amateur range so, although it is just about portable, handing the scope requires a significant amount of body strength.
The CPC 1100 has a superb specification. Telescopes are usually supplied with a 'finder' scope to aid alignment. The CPC 1100's finder is really good quality and very usefully sized, at 8x50. Apart from the large eleven inch diameter, this telescope is computer controlled to an amazing extent. The GPS connection helps with alignment, allowing for an easy and quick start up. The scope is also supplied with Celestron's excellent 'StarBright XLT' optical coatings which ensure that almost all the light that reaches the telescope is focused and not reflected away. The very sturdy tripod mount means that even in light winds, the view through the eyepiece is rock steady.
*** Setting up the telescope ***
The telescope is supplied (and in my case stored) in two parts: optical tube and tripod. Firstly, the sturdy tripod must be set up at the observation site. This is not too difficult as it weighs only 19 pounds and is easy to carry and set up. The optical tube is another matter. At 65 pounds, this bulky (and expensive) tube is difficult to manhandle and line up on top of the tripod. The carrying handles help, but the tube can move within its mount, potentially unbalancing the whole assembly. I'm always relieved (and out of breath) when the optical tube is aligned on top of the tripod.
The magnification of telescopes is varied by the use of eyepieces of different focal length. One the scope is set up, a wide angle eyepiece should be fitted to the scope (this gives the widest field of view; helpful during the alignment process).
*** Alignment ***
After the difficulties of setting up, the easy alignment comes as something of a relief. Previous computerised telescopes required entry of the observer's location, pointing north, then careful levelling. The scope would then 'slew' to several 'guide stars' and the user required to centre them in the field of view. This required knowledge from the user of where the bright stars in the sky where exactly, as centering on the wrong star (very easy to do) caused the alignment to fail.
The Celestron CPC 1100 is much more sophisticated. The telescope is switched on and left to level, align, and detect the time and location (from the GPS module). The user then simply points the telescope at ANY object in the sky and centres it in the eyepiece. This process is repeated another two times and the scope is aligned and ready for use.
This is the easiest and quickest alignment process I have ever seen on a computerised scope and requires no knowledge of the night sky from the user. Within a couple of minutes, the scope can be used and the on board computer keeps the viewed object permanently centred in the field of view ('manual' scopes have to be adjusted every minute or so as the sky turns, moving the target out of the telescope's view).
*** Using the telescope ***
With the telescope aligned, all that remains is to choose a target from the scope's library of 40,000(!) objects. Unlike many computerised scopes of smaller diameter, the CPC 1100 has the power to actually see all of these objects (with a smaller scope Pluto, for example, would be simply too faint to detect through the eyepiece).
The library contains all the planets, named stars, Messier and Caldwell objects, as well as the NGC catalogue. Many objects appear in multiple catalogues as well as having unique names and where this is the case, the object can be searched by any of its names.
Once an object has been selected, the telescope slews to the target, and will hopefully appear in the eyepiece's field of view once the scope has stopped moving. In my experience, the object almost always appears in the view of my wide angle eyepiece: excellent accuracy.
This automated searching is what computerised telescopes were designed for and this Celestron is one of the best. The scope also offers a 'night tour' option which shows the best astronomical objects visible at that time, one by one.
One word of warning, however, the telescope motors are not silent. Astronomical observing sessions are usually at night (obviously! Unless observing the sun, which must be performed with a high quality solar filter fitted to the scope, otherwise blindness will result) and the noise of the slewing motors is noticeable (but not loud). If observing into the small hours in summer, however, any close neighbours may possibly complain.
*** Optical quality ***
Once you have an object in the field of view, what does it look like? Well, the Celestron CPC 1100 has an enormous light gathering capacity almost 2,000 times that of a naked eye! This allows for incredibly faint objects to be seen. Ghostly nebulae, faint supernova remnants, and galaxies so far away that their light left for Earth before the death of the dinosaurs, can all be viewed with the CPC 1100. The telescope captures so much light that the detail available to the observer is much greater than with smaller scopes. For that Wow! Factor, the CPC 1100 is difficult to beat in the amateur market.
The focal length of this telescope is very high at 2,800mm. This has an effect on the magnifications and fields of view available with a selection of eyepieces. The magnification of a telescope/eyepiece combination is given by:
Magnification = focal length of telescope / focal length of eyepiece
The largest common eyepiece focal length is 40mm so this gives a 'minimum' magnification of 70 times. This is actually very high and means that the field of view of this telescope is quite narrow. The telescope is great for high magnification views of the planets, star clusters, and galaxies, but misses out on the wonderful, wide angle views, of sights like the Pleiades offered by telescopes of smaller focal length.
Despite this limitation, I find that the CPC 1100 offers the best view of any telescope I've ever used. The large size offers excellent resolution and the brightness of the images makes viewing even faint objects (which one often has to strain to see with lesser scopes) a pleasure.
Jupiter is high in the sky at the moment and I used the CPC 1100 recently to view it. The images obtained, even at high magnification (x200), were simply superb. The planet appeared as a slightly squashed ball, hanging in the black sky. The coloured bands which encircle the giant planet were easily seen and clearly separated. The famous 'great red spot' was easily visible, too. Jupiter's four large moons could be seen, strung out in a line around the planet's globe. To me, these moons, tiny in comparison to their host planet, appeared as tiny balls, rather than the dots of light I've seen with other scopes.
Viewing Messier 13, the largest globular cluster in the northern hemisphere was simply jaw dropping. At low magnification, this condensed ball of over one million stars looked like a glowing sphere of light. With high magnification, however, the image was transformed. At x200, the cluster filled the eyepiece. Individual stars on the edge of the cluster were resolved from the mass of central stars, giving an almost 3D view. The experience gave me the impression I was hovering over this huge cluster, watching it slowly revolve below me. Amazing!
I have also taken some photographs with the scope using my DSLR. These are of reasonable quality (and improving as I learn), but potential owners should not that, if serious, long exposure, photography is the reason for purchase, a 'wedge' is required at a cost of around £340.
*** Problems with the CPC 1100 ***
I have found very few problems with this telescope. The first is, of course, its manoeuvrability. This is not for the faint hearted: moving an expensive, bulky optical tube, can be a bit scary and back pain-inducing. When observing, I never look forward to packing the scope away again.
The alignment does, on occasion, fail. This means that the process must be repeated. Every time this has happened, the repeat alignment process has been successful, so this causes a delay of a couple of minutes at the most. When this happens, I'm never sure if I have done something wrong or whether the scope is at fault.
The final problem is typical of computers: crashes. On several occasions, the scope has 'crashed' resulting in me switching off the scope and starting again. I don't know what causes this, but it does not happen enough to be intrusive.
*** Conclusion ***
Hopefully, you will have gathered that I'm impressed with my CPC 1100. This is a superb quality, computer controlled telescope with a fantastic specification and the ability to show the user sights he or she will never have seen before.
This performance does come at a price, however. The scope cost £2,649 from Telescope Planet! Readers already gasping, will be appalled to discover that the scope is not even supplied with a power supply (you must supply your own car battery charger for this purpose). This is, of course, an extremely high price to pay, but with telescopes, you do get what you pay for. Hopefully, this telescope will last many years and continue to give me breathtaking views of the heavens.
If you are in the market for a high end amateur scope, the CPC 1100 should be considered. For users who want a smaller, less expensive telescope, however, Celestron's CPC range starts at £1,449 for the eight inch scope. This has the same specification as the CPC 1100, with a smaller mirror.