Celestron CPC 925 and 1100

Celestron has long since discontinued its huge C14 fork-mounted SCT, but that does not mean the fork fan has to be satisfied with 5, 6, or 8-inches. Like its forerunner, the NexStar GPS, the CPC comes in 9^- and 11-inch flavors. These telescopes are identical to the CPC 800 as far as accessories and fittings: same HC, same DC power cord, same decent 50-mm finder, same cheap 1.25-inch diagonal, same inferior 40-mm Plossl eyepiece. Why Celestron insists on including a 40-mm Plossl is a mystery. A 25 mm has nearly the same field of view and is much more comfortable to use. XLT coatings are optional on the CPC 925 and 1100, just as they are with the CPC 800. The CPC 1100 is equipped, like all C11s, with a rear port "reducer" that can be unscrewed to reveal the scope's larger 3-inch port for use with specialized accessories.

Like the CPC 800, these telescopes are wonderfully comfortable to use when set up in alt-azimuth mode. When they are used in this fashion, both the 9^ and the 11-inch are also wonderfully steady (although a set of vibration suppression pads does not hurt). As with the other forks, an optional wedge is required for equatorial mode setup for picture taking. Equatorial setup is where the normally solid 11-inch begins to lose a little steam. As mentioned, tipping a fork-mount CAT over to point the mount's arms at the pole makes for an inherently flimsy telescope. The fairly heavy weight of the 11-inch fork and tube combination (65 pounds) makes the process of mounting the 1100 on a wedge dangerous for one person. In contrast, setting the CPC 1100 on its tripod for alt-azimuth observing is easy as pie for most adults. The telescope uses the same excellent, ergonomic handles as the 800 (and 925), which make it easy for most adults to get the telescope on the tripod head for alt-azimuth use. Still, 65 pounds is a fair amount of weight to be slinging around. If it sounds like "too much," there is always the 925. The CPC 925 is a little lighter, at 58 pounds. The 925 is also less awkward and bulky than the CPC 1100, though, and is therefore somewhat easier for one person to place on a tripod or a wedge.

So, which of these two scopes should you buy? Despite the outstanding optical reputation of the 9^-inch OTA, it should probably be the CPC 1100. Its optics are easily as sharp as those of the 925, and its cost is only about $300 more. That $300 buys nearly two additional inches of aperture, which results in nearly a 70% increase in light (remember, area is the thing, not diameter). Under a dark sky, CPC

1100 images can be spectacular, and if the user must observe from light-polluted areas, DSOs are usually at least "pretty good" compared to the "barely there" the 800 and 925 sometimes offer. Let us say that an alt-azimuth mounted 11-inch go-to scope is pretty close to perfection for a visual observer, offering comfort, a manageable price, and a physical profile that is bearable for most of us.

Celestron CGE 925, CGE 1100, and CGE 1400

The mounting for these telescopes, Celestron's CGE GEM, is exactly the same as the unit shipped with the CGE 800, so see the entry for that scope in this guide for comments on the mount. The only major differences in these packages are the apertures of the OTAs and the number of RA counterweights included to balance the tubes. Accessories are similar to those shipped with the 8-inch: Plossl eyepieces (25 mm for the 9^ and 40 mm for the 1100 and 1400), cheapo star diagonals (1.25-inch for the 9^ and 11, and 2-inch for the 14), and the NexRemote software. As is the case with the CGE 800, the desirable XLT coatings are an extra-cost option for the 925, 1100, and 1400.

The Celestron 9^-inch OTA definitely deserves a few lines of comment here. When this CAT was first introduced in 1996, it attracted a lot of notice from astronomers. For one thing, it was the first new aperture size Celestron had introduced in 16 years. For another, the 9^ soon gained a reputation for optical excellence. The telescope was so good that some amateurs decided it simply could not be an SCT. No, the rumor went, this was not a "real" SCT. It did not have a spherical primary mirror, but a parabolic one. That was the reason for its exceptional performance.

Celestron's designers must have had a good laugh over that one. The 9^ is a normal SCT with a spherical primary, a spherical or slightly aspheric secondary, and a corrector with a complex curve. The reason for its improved performance is that the primary mirror is slightly slower in focal ratio than that of other Celestron telescopes. Instead of the normal f/2, the 9^ has an f/2.3 primary mirror. Because of that, the secondary mirror can be slightly smaller than would otherwise be required. The secondary's curve is a little less "steep" as well (its magnification is such that the final focal ratio of the system comes out to f/10). The smaller, less radically curved secondary is what is responsible for the slightly better performance of the 9^ OTA.

Yes, I said "slightly." Rumors to the contrary, the performance of the 9 ^-inch is right in line with that of the other Celestron telescopes. It is very good, and the image in an average 9^ may be noticeably sharper or higher in contrast than that of the average C8, but the difference is minimal. Most of the improvement in image quality compared to an 8-inch actually comes from the 9^'s superior light-gathering power, about 34% more.

One thing is sure, the 9^ makes a nice set up when combined with the sturdy CGE mount. Although the scope has noticeably more deep sky reach than a C8, the still-light 9^-inch tube (20 pounds), while slightly longer than a C8 OTA, does not even begin to stress out the CGE. Any drawbacks are mainly to do with the scope's higher price ($4,000 with XLT) and the fact that the next step up, the 11-inch CGE 1100, is still relatively easy to manage weightwise but provides an even greater performance increase.

Until the C9^ came along, it was usually the C11 that folks pointed to when they talked about Celestron's "best." The company just seems to have done everything right with the C11 when it comes to optics. That is not to say that the C11 tube shipped with the 11-inch CGE setup, the CGE 1100, is exactly revolutionary. It uses the same optical prescription the C11 always has: an f/2 primary and 5x amplifying convex secondary that produce a focal ratio of f/10. Focus is via a standard moving-mirror system using the same rubber-covered knob and ball-bearing drive as seen on all modern Celestrons. The CGE 1100's OTA, which was carbon fiber back in the NexStar GPS days, is aluminum again, this time painted an inoffensive if not striking shade of gray.

The CGE 925 is an impressive scope, but the CGE 1100 may be the sweet spot in Celestron's GEM CAT lineup. The OTA is big enough to produce truly impressive visual performance, but it is lightweight enough to prevent setup from becoming an exercise in dangerous frustration. An imager or a visual observer who longs for wide-field views will find the 1100's focal length, while starting to creep up at 2,800 mm, is still usable via focal reducers and wide-field, low-power eyepieces. Wide-field imagers will be disappointed to learn that Celestron has stopped equipping the CGE 1100 with the Fastar-compatible secondary mirror mount. In the past, the telescope was available with this desirable option (Chapter 11), as were some of the company's 8-inch OTAs. Celestron has now phased out Fas-tar secondaries for all scopes except the C14. Custom C11 OTAs are still available with this option directly from the vendor Starizona (Appendix 1), however. Starizona also makes a corrective optics set for Fastar use, the Hyperstar. Celestron never got around to producing a Fastar corrector of its own for the 11-inch (Stari-zona can also retrofit a variety of other Celestron and Meade scopes for Hyperstar use). How good is the CGE 1100? Many CAT lovers find the views in the CGE 1100 so good that they never get around to buying a C14.

Nevertheless, the Celestron C14 (Plate 21) has always been and still is the Holy Grail for Celestron CAT fanciers. It is the biggest, the most impressive, and the most expensive Celestron—if it has not always been the best. Even today, when Meade offers considerably larger SCTs, the C14 still impresses. Actually, it is probably a more impressive and better telescope than it has ever been. The dirty little secret about the C14 OTA is that it has often possessed "rough" optics. A lack of smoothness on its mirrors caused light scatter and meant the scope did not live up to its potential, especially on solar system objects. Thankfully, Celestron dramatically improved the C14 OTA during the 1990s. Today, C14s seem almost invariably good; it has been a long time since I have seen an optical lemon.

Featurewise, the GGE 1400's C14 OTA is similar but not identical to the smaller Celestron tubes. Although all the other Celestron SCTs are f/10s, the C14 has stuck with the f/11 focal ratio its designers bestowed on it back in the 1970s. One other thing that is different is the presence of two "mirror stabilization" bolts on the rear cell. These are meant to be tightened against the primary assembly during shipment to prevent the heavy primary from being damaged. Some astroimagers have been able to use these bolts to lock the mirror down, preventing the dreaded mirror flop. Like the C11, the C14 features a 3-inch rear port and concomitantly a larger baffle tube. A rear-port reducer is included and allows the C14 to use all standard SCT accessories.

Plate 21. (CGE 1400) Celestron's largest aperture telescope, the CGE 1400 German mount C14 SCT. Credit: Image courtesy of Celestron.

What is it like to use a CGE 1400? This is an almost-overwhelming telescope. Its XLT coated optics and long focal length mean it can keep up with considerably larger telescopes when viewing medium-small DSOs. In the solar system it frankly leaves the big Dobs in the dust, presenting better views of Jupiter, Saturn, and Mars than a 24-inch Dobsonian. Visual users will love the CGE 1400. Its considerable light-gathering power allows it to deliver stars dimmer than magnitude 15. Unlike Dobsonian light buckets, however, it brings all those CAT niceties to the table— precision tracking, go-to, and comfortable seated observing.

Can anything bad be said about this legendary "portable observatory"? Once you get past the price—a reasonable if not inconsequential $6,600 (including the Fastar-compatible secondary mount and XLT optics options)—there comes the main argument against this big scope: It is big. If the C11 OTA is intimidating at first, an initial encounter with a C14 will be frightening. This thing is the size of a trash can—a 45 pound trash can that must be lifted onto the high saddle of the CGE mount. Over the years, Celestron has advertised the C14 as the world's largest one-person portable observatory telescope. That may be a little truer now that the company has discontinued the enormous fork-mount model, but setting up a CGE 1400, while it can be done by one person, is not for the faint of heart. On the other hand, the CGE 1400 assembly is amazingly easy for two people.

Once the tube is on the CGE mount, how does the package perform? It performs tolerably well. Actually, for the visual observer, it performs very well. The telescope/ CGE combo is steady enough for visual use under most conditions. Imaging is another matter. Although good deep sky pictures can be taken with the CGE 1400, there is no doubt the CGE GEM is somewhat overwhelmed by the monster C14 OTA. A serious imager would be wise to think about a larger third-party mount— a Losmandy Titan, maybe, or an Astro-Physics 900.

If the thought of spending $10,000 for a telescope mount to do imaging does not appeal, order a CGE 1400 with the optional Fastar secondary. Equip it with one of Starizona's Hyperstar correctors, and astrophotography can be done at the more mount-forgiving focal ratio of f/2 (the higher the focal ratio and longer the focal length, the sturdier a mount must be). Be aware that Starizona does not exactly give Hyperstar lenses away; the C14 model is $1,500 (this is less than $10,000, of course).

Let us face it: If you love SCTs, somewhere deep down you want a C14. This telescope is a legend, and if you can deal with the realities that accompany the legend, you might be very happy with this granddaddy of a big CAT. For many of us, the practicalities of everyday life may mean we keep putting off getting one, but we can still dream of the day, perhaps in retirement, when we can build that long-dreamed-of and planned backyard observatory that will, naturally, house our very own C14.

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