Meade 12” LX200 and Celestron’s CM-1100 (Two large aperture SCT scopes compared)

Introduction

Having read many scope vs scope reviews in the past, I have often been a little dubious as to there worth. The comparisons made between scopes in side-by-side tests can often be unfair, for one reason or another. So I have decided to write this review comparing these two scopes, not in a side-by-side test, but based on many months/years of observing with these two scopes.

I have owned the Meade 12” LX200 for 4 years, and CM-1100 for 6 months. During these periods, I have of course had much opportunity to observe/image with both scopes individually, as well as side by side. The following are my own personal opinions based on my use and experience of using these telescopes for many observing and imaging applications, but also as a guide to the potential buyer of the instruments.

A brief introduction to the Telescopes

The Meade 12” LX200 is a 30cm f/10 SCT, offered to the advanced amateur/college on a computerised fork mount, and large heavy-duty tripod. From the picture, as you’ll probably gather the scope is large, and set-up on its equatorial wedge, the whole instrument weighs some ~150lbs. The Celestron CM-1100 is a 28cm f/10 SCT offered on a sturdy motorised CI-700 German Equatorial Mount, made by Celestron. This scope is also directed toward the more advanced amateur, with both telescopes costing around $3500 USD (the Meade now being offered in its newer GPS incarnation.)

Overall, both telescopes offer a high quality, and very capable package, for either CCD or visual use. The Meade, having more features such as automatic slewing/ and a large object database for Deep Sky addicts.

The Telescopes assembly procedures and first impressions.

Don’t be fooled – both these telescopes are large instruments. When assembled, both stand almost 7 feet tall from floor to the upper end of the optical tube. As far as assembly goes, the Celestron is much easier on the Arms and Back, as it breaks down nicely into easily manageable parts (the Optical Tube, EQ mount, tripod.) The Meade however, isn’t as manageable for one person to move around, and the ~70lb OTA/fork requires practice and effort to lift onto the tripod (especially if the Equatorial Superwedge is in place.) The Meade breaks down into 2 or 3 main parts, depending weather the telescope is mounted in an Equatorial or Altazimuth configuration.

The packaging supplied with both telescopes is good, though the celestron is better packed, with a wooden case, with padded inner lining for transport of the OTA. The Ci-700 head is also very well packed. The Meade however for being such a large single unit, could perhaps be supplied also in a wooden case, though its heavy duty cardboard/foam case suffices well.

Optical quality, and Star testing.

When purchasing both telescopes, this area was of the most importance to me. After all, high resolution imaging and observing of the Planets is perhaps one of the most demanding applications one can use an amateur telescope for. Having heard from others at the time, good things about the Meade 30cm SCT, I decided this would be my choice. Looking back, my choice was a good one. After conducting more than one star test with this telescope (always under good seeing to get a clear result), at powers ranging from 235x up to 731x the optical quality of the Meade is good (though not excellent), and I estimate, exhibits around 1/5 to 1/6 wave p-v wave front quality. In-focus star images (under good seeing) present sharp airy patterns, and the telescope has resolved binary stars to the dawes limit (namely gamma2 andromedae in 1999.) Also, both telescopes exhibit only slight mirror shift when focusing, and hold precise collimation well.

Fig 01: Star test images obtained using both scopes, at almost identical sampling on the CCD chip. The effects of atmospheric turbulence are present, though they do suffice as to show the good similarity between the intra/extra focul patterns.

The Celestron was purchased, with hope of obtaining an even better telescope optically, having spoken to and read much about the excellent optics found in their recent models. Needless to say, I wasn’t disappointed. Having also used the C-11 under excellent seeing on several occasions, its optics present a fine star test, with good to excellent quality with I estimate around 1/8 wave p-v wavefront quality. Both telescopes are under corrected, though the Celestron, only very slightly.

Overall, I was pleased with the optical quality of both telescopes, and especially the Celestron.

Planetary performance.

Having used both telescopes extensively for this purpose, I am certainly not in the slightest disappointed with them. The level of resolution and contrast they give visually is very impressive, with the Celestron giving the finest view, and also being able to tolerate higher magnifications.

Scrutinising planetary disks at high power under excellent seeing, has proven the Celestrons superiority in this area. The difference is slight, but unmistakably present. The Celestron will hold very sharp and contrasted views of Saturn at 586x, while the Meade’s upper limit is around 480x – 500x. Also, when observing Saturn, stubble features I have never seen in 4 years of using the Meade were revealed, namely, the many faint brightness minima across Ring B. On October 22nd, 2002, I was treated to my finest ever view of the ringed Planet through the Celestron at 586x. One could almost describe the view as looking at a fine HST image or being in distant orbit around Saturn!.

Though the Celestron has provided such wonderful views, the Meade has also done so. It has produced fine images of a 3.9” arc second Mars, and produced many fine views and images of the gas giants.

Fig 02: Two challenging targets – a 3.9” arc second Mars on November 18th 2002 showing the familiar Syrtis Major and other albedo markings, and Saturn showing a great amount of low contrast detail across the globe and rings, including the 0.05” Encke Division on October 22nd 2002. Mars was imaged with the Meade, and Saturn with the Celestron.

Overall, I have been very pleased with the performance of both Telescopes, but delighted at the Celestron’s - its certainly proof that one need not re-mortgage there home to afford a scope that will provide Planetary views of stunning quality.

Deep Sky and Binary stars.

Having also used the telescopes for Deep Sky visual, and occasional CCD work, both telescopes are also very well suited to this area. Visually, they both provide fine views of a wide range of objects. Showpiece targets such as M13 is resolved into the core, and the views are almost 3D like, with many tiny points of light scattered across the field. M42 takes on the fine delicate appearance that photographs show so well.

But today’s amateur also very likely wants to use these telescopes for CCD imaging. Here, I think the Meade is perhaps superior, as its auto slewing, and large object database, makes finding even very faint targets easy. The Celestron, can be equipped with a similar digital setting circle system, though at additional cost, and without the auto slew feature.

In viewing binary stars, both telescopes perform superbly, resolving stars to the dawes limit. Stars exhibit nice round sharp airy patterns at high power, and colours of the components are well observed.

Fig 03: The well known Planetary Nebula in the open cluster M46 imaged with the Meade at f/6.3 using an SBIG ST-5c CCD using composites of 45 second unguided exposures with the telescope set-up in Polar aligned mode.

For CCD imaging, with a “typical” CCD, both telescopes can reach to below 20th magnitude, for those interested in Supernova patrol, or imaging faint galaxies etc. Also, the FOV, when used with available f/6.3 or 3.3 reducers, can accommodate most objects. The Celestron, has the capability of imaging at f/2, through the use of the optional faster lens system, available at additional cost. This provides a very large FOV for framing larger targets, which is an option the Meade lacks for those interested in imaging large objects such as M31.

The Telescopes Mounting and Mechanics.

Both scopes differ in there mounting, the Meade being a fork mount, with the option of mounting it equatorially on a wedge, and the Celestron, a German Equatorial Mount.

Starting with the Meade, the quality of the RA drive is good, and with programming of the Telescopes permanent periodic error correction feature, the telescope displays around 5” or so of tracking error over an 8 min period. The Declination drive is also fine – provided one rule is obeyed. Don’t expect the telescope to tolerate slewing at 6 degs/sec from object to object for any decent length of time. Failure of the DEC drive is fairly likely, when the auto-slewing feature is used allot, and sometimes multiple failure’s of the declination drive may occur, after replacement. I think perhaps, since these telescopes are marketed to slew at such rates, and are directed toward advanced applications, such as Supernova/Minor Planet patrolling, where allot of slewing is required, perhaps Meade should consider a re-design of the declination drive, and replace the current design with something more robust. It’s also worth noting, that this problem is widely reported in all aperture models from 8” to 16”.

When set-up in Altaz mode, the Meade is very solid, and stable. When set-up on the optional superwedge, stability is compromised somewhat, and the telescope becomes more affected by any wind over 10mph that may be present. The giant field tripod supplied, is of excellent quality, and is very sturdy and well made.

The Celestron CI-700 mount is a rather different package from the Meade. The CI-700 is very well made, with excellent finish. The stainless steel and bronze gears of the drives are also very durable, and well made. In fact, you really get the impression, that the Celestron is more geared toward the more seasoned observer, who wants a good base telescope to “build on”. The drive electronics are also straightforward and well laid out, though the small 6 pin RA drive connector on the drive controller is rather vulnerable to damage, and care should be taken to pack the telescope correctly when transporting it. The telescope tracking is very good, and smooth, with also around a 5” error over the worm period. One quite odd flaw however in this telescopes design, is the excellent, and sturdy tripod is not adjustable in height, which can of course make levelling the mount problematic.

Fig 04: The CI-700 mount drive controller. Note the small connector for the RA motor cable, protruding from its top. One must take care to ensure this isn’t damaged, as it very easily could be.

The drive controller itself, has various features, including 4 tracking rates, and 5 tracking adjustment rates, from 0,5x to 32x sidereal rate. Also, a periodic error correction feature is present, though unlike the Meade, must be programmed each time. Also, one point that should be made, is I advise the buyer to check over the mount for loose screws. My own had a completely loose DEC motor gear, which hadn’t been tightened properly.

The CI-700 also has a polar alignment scope, mounted atop the rear end of the RA shaft. This is only good enough for rough alignment though, so drift alignment is advised.

Overall, the CI-700 is a very nice mount, and is very sturdy, even when the wind is present.

Accessories supplied with the scopes.

The Meade is supplied with a 26mm Plossl eyepiece, 2” diagonal mirror and 9 x 50 finder scope. All these are of good quality, and the finder scope adjustment bracket is good.

The Celestron is supplied with a 26mm Plossl, ¼ diagonal, and 8 x 50 finder. The finder bracket, is not as good as the Meade, as it relies on a rubber o-ring, to support one end, with three adjustment screws. Overall, both telescopes come with a decent basic package, with of course, many available accessories.

The Overall Summary.

I present an overall summary, of the various issues, that will concern most observers: