Celestron CPC 1100 GPS Review by Zane Landers
The Celestron CPC 1100 GPS is an absolute monster of a telescope, and probably isn’t best as a beginner or “only” instrument – but boy, does it deliver.
Celestron has been offering Schmidt-Cassegrains atop double-armed fork mounts since their inception in the 1960s, and the CPC series telescopes are the last remnants of that era. The CPC 1100 is the largest of the three aperture options in the CPC line, and Celestron doesn’t sell a 14” CPC for a good reason – these fork mounts are massive! The CPC 1100 is a very capable instrument, but between its price tag, weight, and complexity, you should probably own or have owned at least one or two other telescopes so you know what you’re getting into.
The C11 Optical Tube
280mm (11″) Aperture
2800mm Focal Length
The C11 has been around since the late 1970s when Celestron opted to introduce a new telescope to fill the gap between the portable C8 and the monster, observatory-class C14 (the C9.25 came much later). The C11 is an 11” (280mm) f/10 Schmidt-Cassegrain with a focal length of 2800mm, achieving this focal length using a spherical f/2 primary mirror and a convex, 5x magnifying secondary mirror. The Schmidt corrector at the front removes the spherical aberration otherwise inherent in the optics. The C11 focuses by moving the primary mirror along a rod inside the telescope; accessories and adapters screw onto the back. You can also remove the secondary mirror to convert the telescope to an f/2 Schmidt camera with Starizona’s HyperStar corrector/adapter system, making the scope capable of short-exposure deep-sky imaging with or without an aftermarket equatorial wedge. Various adapters, focal reducers, and other accessories are also available to attach to the C11.
The CPC Fork Mount & Tripod
The CPC mount design is an alt-azimuth GoTo fork mount design, perched atop a massive steel tripod. To set the scope up, you simply perch the tube/fork assembly on the tripod, align it with a few stars, and you’re on your way. Obviously, this assumes you have no trouble hoisting the massive 65 lb scope/fork combination onto the tripod, but the good news is that there is no mental gymnastics to do after that. The GoTo and tracking of the CPC mount are extremely accurate, and you can do planetary astrophotography or short (under 30-second) exposure deep-sky imaging without an equatorial wedge. A wedge is simply a big tilted plate to convert the CPC fork mount into an equatorial mount; you can use it for long exposures either with an f/6.3 reducer or f/2 HyperStar system for fabulous deep-sky imaging provided you use autoguiding. The CPC mount supports Celestron’s computerized scope accessories like the StarSense Auto-Align or a WiFi dongle to control the scope via your phone or tablet.
You can also unlock the clutches on the mount to steer it manually, but this will ruin alignment of the GoTo system. Manually aiming and tracking with a 2800mm focal length is also a bit of a pain, and if you’ve already gone through the trouble of assembling this beast, aligning it on the sky isn’t too much extra effort.
The “GPS” part of the CPC 1100 GPS is simply a GPS unit that automatically updates the time, date, and location so you don’t have to enter it into the scope. These units tend to fail over time but it will not inhibit using the telescope in any way; a WiFi adapter will obviate its use anyway.
The CPC 1100 GPS comes with a 9×50 finder for aligning and aiming it, a 1.25” screw-on visual back, a 1.25” prism star diagonal, and a 1.25”, 40mm Plossl eyepiece yielding 51x magnification and a true field of about ½ of a degree across (just around the angular size of the full Moon). You’ll want to get additional eyepieces for varying magnifications, along with a 2” star diagonal to enable a wider field of view, so be sure to account for those in your budget. The good news is that an f/10 telescope does not need fancy eyepieces to perform well.
What can you see?
The C11 is a powerhouse on almost every type of target – provided the target is small enough to fit in a field of view under 1 degree across, which excludes some nebulae and star clusters.
Here’s what you can expect to see of Solar System objects:
Mercury and Venus are blank crescent or gibbous orbs, with no discernable features – Mercury lacks any large, contrasting details and Venus’ surface is of course obscured by clouds.
The Moon is dazzlingly bright (though still harmless) and shows details under a mile across on a still night with good seeing.
Mars’ polar ice cap and a few dark markings should be obvious when the planet is close to Earth. Its moons can also be glimpsed with careful observing techniques, and any dust storms should be immediately apparent as they obscure all other surface details.
Jupiter’s cloud belts are vibrant and explode with color, and the Great Red Spot is easy to see. Jupiter’s 4 large Galilean moons all appear as disks with good seeing, and their shadows can be seen on Jupiter’s cloud tops when they transit. Ganymede may show a surface detail (a brown northern hemispheric feature called Galileo Regio) the other moons are noticeably not uniform bright balls with good seeing.
Saturn’s rings are gorgeous, and the Cassini Division in them is usually apparent. On a very good night the Encke gap in the rings can also be seen. More than half a dozen moons are visible, along with cloud belts on Saturn itself.
Uranus’ featureless disk can be resolved with the C11, and a few of its moons are faintly visible (glare from Uranus itself can make it difficult).
Neptune is a bluish star-like dot, but its moon Triton is fairly easy to see.
Pluto can be seen as a star-like dot under dark skies if you can figure out which one of the hundreds of points of light in your field of view it is.
Deep-sky views with any telescope are strongly affected negatively by light pollution. Under city skies, you’re limited to star clusters and bright nebulae. Under dark skies, however, the C11 can show you thousands of galaxies, dozens of which have dust lanes or traces of spiral arms. You can resolve globular clusters into stars. And the Orion Nebula is jaw-dropping, especially with a nebula filter.
Heavy Optical Tube
Super-Long Focal Length
The C11 optical tube weighs 28 lbs bare, which is already a hassle to hoist up high onto a mount/tripod. This balloons to 65 lbs attached to the fork mount, and you cannot realistically separate the two for transport (or really at all, unless you are semi-permanently removing it for use on another mount). Thus, we would really recommend you have a helper or two, a garage and dolly to roll the scope out of, or some kind of permanent observatory – otherwise, you could throw out your back, drop the telescope, or simply find yourself not using it much as a result.
The super-long focal length of the C11 optical tube means that it is hardly a good scope to learn astrophotography on, and viewing deep-sky objects can be annoying if they do not fit in the field of view (e.g. large clusters or nebulae).
The Celestron CPC 1100 GPS is a massive commitment but provides massive capabilities and a telescope that will last you a lifetime. Just be sure to take into consideration how heavy and expensive it is before making your decision.