Here's the review:

A Review of the "new" Celestron G3 and comparison to the Meade ETX - by Darren Hennig

    Well, we're rolling around close to Christmas again, and I guess all the telescope companies are really going for it in 1998. Pretty much everyone by now has seen the new packaged small scopes by Celestron, but there hasn't been alot of talk about them yet. I recently acquired a G3 [over the ETX!] and I'll tell you my first impressions and performance of this neat and versatile system, and compare it to the scope that has everyone talking lately - the Meade ETX.

    Before I continue, I must say that in all fairness it was a very difficult decision choosing between the G3 and the ETX, for both scopes are of the excellent Maksutov-Cassegrain design, are highly portable, are diffraction limited, and have a 90mm [3.55"] aperature. There are a few key advantages [I felt] that the G3 had over the ETX, and I'll go on about these later.

    Right out of the large box, the equipment is VERY well protected - you truly feel that you've bought a lot of "stuff" for your money! The unit I received had the finder already attached, and the mount only requires minor assembly to be ready to go! My first immediate impressions of this scope and mounting system is that it was very well made - and even after using the unit for several weeks - I still feel that I have definitely gotten my money's worth!

    First, the overall appearance: The G3 looks [AND IS!] a very well made telescope - and is quite light, at just 4lbs. Celestron has marketed this scope, and a rubber-armored version as their C90 spotting scope for many years - This G3 is mainly a packaging difference, otherwise the units are the same. At just 8" long and 4.5" at the widest, the G3/C90 employs a helical focus arrangement - this is similar to the way one would focus a large camera lens. The focal travel is very smooth, even in fairly cold temperatures [The lowest I've used this unit in is -10C or about 14F], though it does stiffen up a bit. There is a TREMENDOUS amount of focal travel, and the unit will go to a close focus of just under 5', just as promised by Celestron. Images are easily sharpened by the helical focus, and the large focal travel means that the unit will accomodate easily a host of visual and photographic accessories without the fear of failure to achieve focus with them in place! This makes this scope extremely versatile as a nature study spotting scope, a high quality 1000mm lens, and as a nice portable astrophotography platform, to name a few other applications.

    The mount for the money is quite good, and it is the same for the G5 unit - it is of the German equatorial [GE] type. It is fairly solid, sturdy, all aluminum metal and well made, tipping the scales at about 18lbs - portable enough to go anywhere. RA/Dec slow motion controls are smooth, and there was no "play" in my unit that I recieved; Tracking is quite good on the motorized version, and there was observed even at 230x no "catch up" or out of field drift was observed before the unit began tracking the target. I've seen several ETX users needing to employ a bit of ingenuity to get their systems to track reliably. This is about as much of a "plug and play" system as I've seen so far. Without even looking at the instruction manual [which, by the way is a bit over simplified and not too informative], the whole system could be assembled out of the box for use in about 10 minutes! The mount includes an accessory tray, which doubles to solidify the mount, setting circles usable in either hemisphere, a good counter balance system, and manual slow motion controls for both axes, which are very accessable and easy to use. It also has a latitude adjustment with a type of micrometer fine tuning; The top of the mount can also swivel 360 degrees to allow for proper polar alignment and adjustments. There was extremely little backlash on either axis in the mount I received. The motorized version comes with a RA motor drive that runs off 4xD batteries, and Celestron claims about 20 to 24h of continuous use per set - I've used mine for about 18 hours total tracking at below 28F with alkaline cells and its still going. The motor drive mates nicely onto the mount, and has a spring tension and a locking screw to keep it in contact with the main drive gear during tracking - more on this later. Switching from tracking to manual is very simply provided by a small lever which separates the motor gear to the main gear, and engages immediately when the two are brought together via the lever. The control unit allows for dual hemisphere use, with 2X and 4X as well as a stop provided for the tracking rates. 4X is in either direction, but the 2X is only in the forward direction. The G3 comes with a standard 1/4" threaded base to mount either on a tripod, or directly with the base on the GE mount - care must be taken to properly align the scope to the declination axis, or there will be errors, but switching from one mount to the other is very easy! The mount should be useable for loads up to 10 lbs or so, but make sure that the appropriate amount of counterbalance is employed if you are thinking about using this mount for scopes other than the G3 or the G5, as this mount is designed for small light loads.

    The G3 held up to the C90's reputation. Images are crisp sharp over almost the whole field, with a small amount of vignetting when using moderate to high powers with the hybrid diagonal that comes with the unit. Stellar images definitely display the Airy disk patterns, even at high magnifications. Images were [almost nearly - hardly a difference] as good as my friend's ETX in image contrast, although I didn't have a true dark sky when initially comparing mine to his. Image brightness was also comparable, again I'm almost sure a bit brighter than the ETX due to the difference in focal ratios: f/11 for the G3; f/13.8 for the ETX. The wide field performance of the G3 was [as I suspected it would be] far better than the ETX I'd used; I was able to grab just over 2 degrees of sky easily with my 40mm Plossl [25x], making it a nice wide field scope for larger deep sky subjects. I'm planning on getting an f/6.3 reducer/corrector in the future, which should lower the f-ratio to f/7 [700mm]; even with a good 52 degrees of apparent field on my 40mm eyepiece, that should give me about 3 degrees of sky! Rich field here we come!

    There are some quirks with the unit, and definite improvements can be implemented to make this one heck of a little scope! The first and most obvious is the hybrid diagonal that comes with the unit. The visual back for the G3 is a .965" diameter. Most of us have 1.25" accessories for other scopes, and the quality is typically better in this range of barrels. The diagonal adapts to the 1.25" fine, but it is plastic. All plastic, save the mirror and the tightening knob. I was a bit disappointed in this, given the quality of everything else in the package! I wouldn't use this diagonal in cold temperatures, as the "chrome" was observed to flake off slightly after use awhile. Had I not been aware of this, I might have risked getting the tiny schards into the optics over time. Also, the plastic diagonal doesn't really offer a firm holder for heavier eyepieces and accessories, although it does stay in place when the screw is tightened to keep the eyepieces at the desired viewing angle, though you have to be careful with heavier loads, or slight mis-collimation could result when repositioning the eyepiece. I also observed some restrictions in the visual field with my wider angle eyepieces, due to the built in "stop" in the eyepiece holder designed for both .965" and 1.25" barrel size. I suggest getting either a better .965"-to-1.25" adapter [$20], or better yet, do yourself a favor and pickup a LAR [Large Accessory Ring] and a 1.25" visual back adapter like I did. That costs about $60, but well worth it! Now you have a very firm back for just about anything you wish to place at the focal end of the scope! Orion is one of the best sources for these. I can now use my 1.25" higher quality star diagonal, and my 45 deg erect image diagonal easily. I needed a 6-32 threaded screw [~3/8" long] to cover the hole that the tightening knob used for the .965" back for adjustment, since it was not needed once the 1.25" back was put on. The finder is an erect image 8x20 type. It's cute, but almost worthless when more demanding viewing is desired; It is positioned to be JUST barely convenient at higher elevation viewing, and the images in it are too dim for general suburban use, save only the brighter targets, such as the moon, planets, and a few bright stars. I modified my 6x30 LER finder's base with a file to narrow the gap in the screw holes to accomodate use on the G3, and employed some thin foam weather stripping to provide a clean look to the package when on the G3. [the radius of curvature of the 6x30's base was slightly larger than the G3's, leaving a 1/16" gap at the ends of it, being filled in with the foam]. The 6x30 made quite a difference!

    Finally, the unit I got had the RA motor directions reversed, so S is N in rotation. I talked to Celestron about this, and they had several other calls about this batch. It was not a big deal for me, so I use the N/S indicator to read the direction of my local meridian instead of hemisphere; normally once set, I would only have to concern myself with this if I went "down under". Celestron has stated that they have corrected the problem, and future units should be fine. For the adventurous, you could reverse the leads on the manual switch and it would be fine, too.

    The key advantages that I feel the G3 has over the ETX is value, versatility, and expandability. The motorized version is well worth the money! This system would be better than the ETX [as is] for general field use, as the mount can be run independant of a picnic table! Images are a tad brighter [contrast very close to] the ETX, and the size and expandability with more standard accessories is a real plus. Tracking and aiming is superior with the G3, and ease of focusing is also a noteworthy advantage. The optics are PERMANENTLY collimated due to the helical focal arrangement, and the unit has no moving parts save the main scope body. No annoying flip mirrors, no moving parts, no problem! The optics on mine have yet to "fog" significantly after coming in from well below freezing to room temperature, suggesting very well coated and sealed optical components. The excellent wide field performance and 5' close focus capability of the G3 makes it a good all-purpose piece of equipment. Switching from one type of mount to another is more convenient - just one screw and you're done! The multi-speed capability of the motor controls and their ease of access via a control unit means better applicability in astrophotography and high magnification applications. Finally, the German equatorial mounting arragement is superior to the [too short!] dual forked system on the ETX. At some latitudes, the ETX can't see close to the horizon, due to interference of the mounting base, and the ETX's mount can't easily be adapted for use with other scopes!

    All in all, I'd say Celestron has a winner with the G3. The overall value of the package and performance of this scope should allow it to do well against the ETX by Meade. The G5 is Celestron's very well-known C5 Scmidt-Cassegrain scope, known for years as a winner, so if you want aperature over portability the G5 would also be a great choice. Either way, I'd be hard pressed to find a better value than the G3! If a G3 is going to be a serious choice for you, do yourself a favor and get both the larger finder scope and the LAR/1.25" visual back as well as a good 1.25" mirror diagonal - then you have a solid, reliable and worry-free piece of equipment with about as many applications as you can imagine.
 

- Darren Hennig,
  Edmonton Alberta Canada.