Celestron CPC 925 GPS Review by Zane Landers
The Celestron CPC 925 GPS is a fairly versatile scope and is great if you don’t plan on doing much imaging. However, it isn’t the most convenient, capable, or portable option for its aperture and price range, even when compared to the other C9.25 tube/mount packages Celestron offers.
Celestron offers their C9.25 XLT optical tube with various different mounts, such as their NexStar Evolution series, various German equatorial mounts, and of course the CPC fork mount. The C9.25 is slightly better for its aperture than other Celestron Schmidt-Cassegrains due to a slightly different optical design and thus performs much better than a typical C8 than its specs would otherwise suggest, rivaling the larger C11 in lunar and planetary views (though not image brightness on deep-sky objects).
The CPC 925 GPS, which consists of a fork-mounted C9.25 XLT optical tube, is a holdover from earlier periods in Celestron’s history when they were known for their double-armed fork mounts. While a good scope, the CPC 925 is quite heavy and expensive for what you are getting.
The C9.25 Optical Tube
235mm (9.25″) Aperture
2350mm Focal Length
The C9.25 is a 9.25” (235mm) Schmidt-Cassegrain telescope, with a spherical concave primary mirror, a convex secondary mirror, and a Schmidt corrector lens at the front (which may look like a flat piece of glass, but actually has a very complex curve). It’s an f/10 (producing a 2350mm focal length) like Celestron’s other SCT offerings, but uses a slower primary mirror (around f/2.5) and thus a more weakly curved secondary mirror which amplifies the focal length by only 4x rather than 5x. This has the side effect of amplifying issues with collimation or optical quality less, and an f/2.5 mirror is more lenient with bad collimation as well as being slightly easier to make to a high standard of quality.
Low sales volumes also mean that the quantity of C9.25s in existence is much lower than most of Celestron’s other aperture SCTs, which translates to less wear on the tooling used to produce the optics and so forth. All this means that the C9.25 is oddly long compared to its diameter versus other SCTs which are squatter, and the C9.25 is more likely to perform well.
Like most SCTs, the C9.25 reaches focus by moving the primary mirror along a rod inside the tube, adjusting the spacing of the optics and moving the focal plane. You attach a visual back (or star diagonal directly) to the back of the telescope and can easily install standard SCT accessories like Celestron’s f/6.3 reducer-corrector or a camera adapter. The secondary mirror of the C9.25 is removable to insert Starizona’s HyperStar corrector lens, which turns the C9.25 into a super-fast f/2 Schmidt camera for astrophotography at just 470mm focal length.
The CPC Fork Mount & Tripod
The CPC 925 uses a double-armed, alt-azimuth GoTo fork mount. All you do to set it up is put the scope/mount head on the tripod, level the tripod, align the scope on 3 stars, and you’re done. The built-in GPS automatically updates the time, location, and date in the hand controller. The tripod is super heavy duty, the whole mount is sturdy and uses metal gears, and the electronics could easily last a lifetime if taken good care of. Tracking and GoTo accuracy are very good – just fine for visual use or planetary imaging – though you’ll need an equatorial wedge for long-exposure astrophotography of deep-sky objects.
The CPC 925 GPS includes a 9×50 straight-through magnifying finder for aligning the telescope on the sky, a 1.25” screw-on visual back, a well-made 1.25” prism star diagonal, and a 40mm Plossl eyepiece, which yields 59x magnification and a true field of view slightly bigger than the full Moon at about 0.6 degrees across. Additional eyepieces are essentially mandatory to get the most out of this scope, and a 2” diagonal for a wider field of view would be a good idea.
What can you see?
The C9.25 is a great scope for viewing Solar System as well as deep-sky objects. 9.25” of aperture is capable of taking in a lot of light for deep-sky viewing as well as resolving tiny lunar and planetary details on a steady night.
Here’s what you can expect to see of Solar System objects:
Mercury and Venus won’t show much besides their phases due to Mercury’s tiny angular size and low contrast, and Venus’ cloud tops obscuring its surface.
The Moon shows details mere miles across such as craterlets, ridges, and mountain peaks.
Mars only reveals significant detail when the planet is close to Earth, but for a few months out of every 26-month period Mars will reveal its polar ice caps and a few dark markings on its surface in the C9.25, along with any dust storms.
Jupiter’s Great Red Spot along with the disks and shadows of its moons are fairly easy to see with the C9.25, and the cloud belts on the planet look gorgeous too.
Saturn’s rings are quite the spectacle with the C9.25, and you should have no problem seeing the Cassini Division within them, along with cloud belts on Saturn itself. Several moons can be seen too.
Uranus is tiny and lacks any cloud details, but its disk is resolvable with the C9.25 and you may be able to spot a couple of its faint moons.
Neptune may be hard to distinguish from a star at all with the C9.25, but its only large moon, Triton, is fairly easy to see next to it.
Pluto is just barely visible as a dim, star-like point (amidst a sea of dim stars that look identical) with the C9.25 under dark skies.
The quality of your views of most deep-sky objectswith the CPC 925 GPS, or indeed any telescope, is dictated by light pollution. Severe light pollution won’t allow you to see detail in galaxies or resolve globular star clusters clearly, though open clusters and small planetary nebulae are still satisfactory. Under dark skies, however, you’ll be able to resolve the outer member of many of the brighter globular star clusters in the sky along with dust lanes in dozens of galaxies – as well as being able to see thousands more as faint smudges. Bright nebulae like M42, the Orion Nebula, and M17, the Swan, look fantastic too.
Heavy & Large
Equatorial Mount is More Capable
The CPC 925 optical tube and fork mount are basically inseparable and weigh about 42 lbs, which may not sound bad until you realize that you have to lift that up onto a tripod and align it perfectly with the center pin. The dismantled scope is also hardly compact, taking up more space than a typical 8” or 10” Dobsonian.
While the CPC 925 is easy to use and works well for planetary imaging, or deep-sky imaging with an equatorial wedge, an equatorial mount is more flexible in capabilities and breaks down into smaller and lighter components. The Advanced VX-mounted C9.25 is significantly lighter, more portable, and arguably more capable, all at a lower price than the CPC, with the only downsides being the increased complexity of assembly and alignment.
The Celestron CPC 925 GPS is a great scope if you want simplicity, reliability, and convenience. It’ll easily satisfy you for years to come and last a lifetime. However, if you want a cheap, versatile, or lightweight instrument, there may be better choices.