Pirich's Full Review: Celestron CPC 1100 GPS (XLT) (70 x 280mm) Telescop...
I have remarked before about how the C11 is a fairly big scope. It is also a really capable scope. When looking at the trapezium in Orion, the six stars you may need to strain to see in an 8" scope are easy. Saturn and Jupiter just pop out with detail. And with the fork mount, it is actually fairly compact, though it is really at the practical limit of portability. But at the moment, they are $2600, and this really is a lot of scope for the money. I have more general information on choosing a telescope in my article on Picking at telescope.
Background
The reason for a telescope like this is there is a curve for resolution versus telescope diameter which tells the story of several rules of thumb. The larger the diameter of a telescope, the finer the resolution it can resolve. In practical terms, this why a look at the moon with a 60mm scope is impressive, then seeing it through a 90mm one is like seeing it for the first time, and then a 5" scope causes the feeling all over again. But this doesn't keep going- there is a point around 6" in diameter where the movement of the air in the atmosphere starts to make getting a perfect image impossible (this is why Hubble is in orbit).
The 8" diameter C8 is on the side of the resolution curve where it is flattening out, and the 11" is even further in that direction. When looking through the eyepiece, the difference in an image of Saturn between a 5" scope and the 8" is all in fine detail becoming easier to see. Between the 8" and the 11" scope, what happens is just about everything you can see in the 11" scope can be found in the 8" image, but it is just in easier reach of the larger scope.
The CPC 1100 has its roots with the earlier Celestrons in the 1970s. And it has been fork mounted for a long time. One of the peculiar things with the fork mounts is how specific they are to their telescopes- the tines are sized for that one optical tube. So, looking at older C8 series scopes, such as the older Celestar 8, Ultima 2000, and NexStar 8 GPS, or the contemporary CPC 800, the fork and optical tube assembly is essentially the same size, though each of these is a different fork and drive base from the others. The same thing is true with the larger 11 inch diameter Schmidt Cassegrains, and the CPC 1100 is almost exactly the same size and weight as its predecessor, the NexStar 11 GPS. So anyone getting one of these should understand it is big. It is heavy. And it always will be.
The fork mounted C11 is the largest scope Celestron currently has permanently attached to its drive base this way. And that puts that single component at 65 lbs. Meade is still selling 14" and 16" scopes mounted this way, and that's getting really heavy. The main alternative to the fork mounts for these scopes are German equatorial mounts, such as the older CM-1100. though they are less compact, and the total system weight is quite a bit higher, it does have a benefit from the individual parts breaking down to pieces of 35 lbs. or less.
Description and Usage
The CPC 1100 uses the same drive base used on the CPC 800 and 925. The only real difference is the length of the fork arms to allow room for the optical tube to swing past the hub. The twist type clutches are the same type as the other variants, and so is the control handset.
The optical tube has some new features, like the smaller variants, where a newly contoured back bucket and forward cell are used. The interior of the optical tube and the finder scope are essentially the same as they have been since the early days for this design.
The mechanism for the optical tube is considerably larger than the C8, which shares a focuser knob with the NexStar 6SE and the C5. The CPC 1100 has a bigger focuser, and you can feel a larger optical elment is moving in there when you move between direction. Unlike the smaller scopes, the longer 2800 mm focal length of this telescope means the field of view is never very big, so large extended objects like the Orion Nebula are largely a lost cause. With that said, this mount is well suited to piggyback cameras or smaller scopes which can do wide fields, like the AT66ED, or the larger Onyx 80ED. Compared to the size of the parent scope, these are fairly small, and the nice thing about the new 3 star alignment system on these scopes, the startup does not include swinging through the fork arms.
To get ready for photography, this scope needs to be mounted on a wedge assembly. The OSHA limit for carrying loads is 50 lbs. The CPC 1100 weighs 65, though the layout of the side handle with a cup handle makes this easier, it is still heavy. But to get it onto a wedge, it is going to need to attach at an angle. I am torn between whether this should be a 2 person task or if three are needed to do this. In any case, the task is not something to be done lightly, and is just one reason why putting the telescope on wheels like Jim's Mobile wheelie bars or Scoperollers.
Since it really is tempting to mount other telescopes on these, controlling the need to take it down counts. One serious problem just about everyone has at this point is urban light pollution (the power problem says we need to start backing off on this lunacy and save some electricity). The CPC 1100 can operate without problems in the city on objects like planets and the moon. In fact, the image in the CPC 1100 of the moon is so bright it really does need a filter to dim the image to make it comfortable to look at. But on the deep sky, the 40,000 objects the NexStar controller will drive this scope to include a long list of things which really are hard to see in the city. A Light Pollution Reduction (LPR) Filter. The penalty is a reduction in brightness, but they really do reduce the light pollution further.
Another trick to keep in mind is to try moving up the magnification. As the image gets dimmer, the human eye has an easier time determining what is part of the object and what is not. The technique simply does not work for photography, but it is effective for visual observations.
If you are serious about high speed photography, Starizona (www.starizona.com) has a system where the secondary mirror comes out an a lens system called hyperstar which will run the telescope at f/2, for a digital camera, which is only a 560mm focal length, so a lot of the field of view problems can be dealt with.
Conclusion
The CPC 1100 is a sensiby ideal version of the venerable C11. Like the other scopes in this generation of fork mounted scopes, the 40 years of design experience with this overall design are clear in its function. The fact it is available for $2600 really means if you really want one, then it really is economical for what you get. I can only recommend it to an avid observer or a group because it really is big. But then again, the views of planets are pretty good.
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