The LX400 (Plate 20) does not come in an 8-inch version, so I have chosen to place the smallest model, the 10-inch, with the 8-inch SCTs rather than with the big CATs. That is because this is a remarkable scope in many ways, one that is worthy of consideration by anyone in the market for an SCT of any size, not just something for folks suffering from the dreaded aperture fever.
What makes the LX400-ACF "remarkable"? There are a number of things, but basically this was the first new idea in SCTs to come down the pike in a long time when it was introduced in 2005. It still stands alone today. For mass-produced SCT buyers, this is as advanced as it gets. To start with the optics, like the Meade LX200-ACF, the LX400 features the optimized "aplantic" SCT design. Meade did not stop there, however. The LX400 optics set has a focal ratio of f/8 rather than what has
Plate 20. (LX400-ACF 10-inch)
The smallest member of the LX400 family, a 10-inch LX400-ACF. Credit: Image courtesy of Meade Instruments Corporation.
been the standard for SCTs over the years, f/10, so its field of view is wider eyepiece for eyepiece, and imaging exposures can be shorter and will deliver wider fields than those taken with a standard SCT at f/10 without the need for reducer/correctors. It has been the norm for SCT-using imagers to have to fool around with these and other "focal-reducing" lenses to achieve shorter exposures and wider fields in the past. With the LX400, the telescope can often be used at its "native" focal ratio, eliminating problems such as vignetting caused by focal reducers.
The LX400-ACF optics are at least incrementally better than the previous SCT standard, but it is really the "everything" else that is the draw here. Let us look at the optical tube first. The question that comes to mind when you see your first LX400 in person would probably be, "Where is the focuser?" There is no focus control on the back of the LX400 OTA. There is no mirror lock, and none is needed. As mentioned, rather than focusing by moving the primary mirror, the LX400 focuses by moving the secondary mirror. Actually, the entire corrector assembly at the front of the scope moves back and forth as the telescope is focused. This is done with small motors and is controlled with a couple of buttons on the Autostar II HC. The primary mirror is firmly and permanently locked in place. This system finally eliminates the focus shift and mirror flop that have disturbed SCT users since the scopes were first introduced.
The focus motors do not just focus the LX400, however; they can also be used to collimate it. By activating combinations of the focus motors, the telescope can be optically aligned by pressing buttons on the Autostar. What if a new user starts playing around with this motorized collimation and gets things so far out of whack it is difficult to get a decent alignment back? A push of a button will restore default factory collimation.
One thing that has always been irritating about Celestron's more expensive fork-mount telescopes is that while they have the wonderful slip ring arrangement on the drive base to eliminate cable wrap, a dew heater (with cable) must usually be installed on the corrector to keep the lens dry—and back comes cable wrap. Why does an SCT not feature a built-in corrector heater? Meade listened. The LX400 includes an integral corrector plate dew heater that is controlled by the Autostar II.
What else could Meade pack into an SCT OTA? I have just begun to describe the features of this amazing scope. On the rear of the tube, there is an advanced control panel that features an additional port for the hand control, a Meade "auxiliary" port, an ST-4-style autoguider input, and most important, three USB (universal serial bus) ports for external computer control. Why is this most important? Computer manufacturers have eliminated serial (RS-232) ports on almost all laptop PCs. Unfortunately, until the LX400 came along, scope makers still insisted on using RS-232 serial data for computer control. That meant paying extra for a PCMCIA serial adapter card or trying to make a USB-to-serial converter cable work (often an impossibility). Meade includes special driver software with the LX400 that should allow off-the-shelf astronomy software to use the scope's USB ports.
As if all the above were not enough, the LX400's tube is made of low-expansion carbon fiber, material similar to what Celestron used on its now-discontinued GPS series. LX400-ACF-equipped astroimagers will not have to keep refocusing all night long as the temperature changes. Carbon fiber is also slightly lighter than aluminum and keeps the weight of these hefty scopes down. Carbon fiber tubes do take longer than aluminum OTAs to acclimate to outdoor temperatures, and the RCX addresses this problem handily with the addition of a built-in (filtered) cooling fan on the rear cell.
The fork mount and base of the telescope are a little less innovative than the tube. The mount is really not much different from that found on the LX200-ACF scopes. The drive base control panel does contain another USB port at least. The drive/gear system has been somewhat improved over that found in the LX200-ACF 8- to 12-inch telescopes, but performance is fairly similar. The LX400 includes both PPEC and the Smart Mount pointing accuracy improvement feature, just like the less-expensive scopes.
As befits Meade's top scope, the LX400's accessory lineup is impressive, if not as lavish as might be supposed. The scope comes standard with a UHTC-enhanced 2-inch star diagonal. The eyepiece shipped with a scope is a long way from the 25-mm Plossls I have been accustomed to finding in the boxes with the other SCTs. The LX400's single included eyepiece is a 24-mm 2-inch Meade Series 5000 Ultraw-ide with an 82° apparent field of view. The tripod is also something of an advance. It is heftier than Meade's standard field tripod and features an innovative "trigger release" mechanism that makes extending and collapsing the tripod legs easy.
All the above sounds good, but what is an LX400 like in the field under the stars? Thanks to the kindness of a Meade representative, I had the opportunity to give the 10-inch a hands-on tryout at the 2006 Cherry Springs star party where I was speaking. My first impression was that it was big. I could not believe I was looking at a 10-inch CAT. The LX400 OTA is larger than the "normal" 10-inch to accommodate all the motorized gizmos needed to handle focus and collimation. Combine that with the extra-heavy-duty tripod, and I thought I was looking at a 12-inch.
Getting the telescope going was simplicity itself. Like all Meade's GPS-equipped north-and-level scopes, when setup in alt-azimuth mode, the LX400 practically aligns itself. Turn it on, the scope gets a GPS position, date, and time fix, finds north and level, and heads for the first of two alignment stars. Center these two stars in the eyepiece, hit Enter, and an evening of productive observing can be enjoyed with the aid of deadly accurate go-to. Like the LX200-ACF, the RCX400-ACF does not have to be placed in home position before beginning alignment— the scope does that itself.
How good were the images the LX400 presented once the go-to had been aligned? They were very good indeed. Stars did seem sharper out at the edge of the field than they do in a "normal" SCT. But, as with the LX200-ACF scopes, the images were really only slightly better. They might make a great deal of difference for an imager, but most visual observers spend their time looking at the center of the field, not the edges, so the improved flatness of the ACF field would not be as big a factor.
What were the drawbacks? One was the noise level of the motors. No, they were not any louder than those of the LX90 or LX200, but they were not any quieter, either. At a price almost twice that of the LX200-ACF, you would expect something that sounded better. Now, admittedly, this was mainly an aesthetic consideration. The scope tracked well (visually), and the go-tos were great.
How about the motorized focusing? It is good, once you figure out how to use it. The Autostar does not have a dedicated focus control key; instead, the number 4 key is used to activate the focuser. Pressing this key while "focus speed" is displayed on the Autostar will adjust focuser movement from fast to slow. A second press of the 4 key after the focus speed display is gone (after 2 seconds) allows the user to access focuser "presets," user-defined focus positions for a particular camera or eyepiece. Focusing itself is done by pressing the up/down arrow keys. All this sounded reasonable enough when reading about it in a brightly lit motel room. Out on the dark Cherry Springs observing field, it was difficult to remember which button to mash to focus the thing. Once the correct button is pushed, focusing is easy and precise. The focus motor emits the usual Meade coffee grinder noise, just like the drive motors.
In fit and finish, the scope was fairly impressive. The tube is a thing of beauty. Its distinctive shape and the carbon fiber's elegant grayish finish stand out. The tripod was also very professionally put together and attractive. The fork mount was another matter. It was not much different from those on any of Meade's other scopes—workmanlike, but not exactly beautifully done. As a matter of fact, the castings on the RCX fork were somewhat the opposite; in a couple of places, they had the look of being "sand-cast in someone's backyard." Admittedly, this was an early example, and the mount did perform well. Last, the LX400 is a big, heavy scope, even for a fork SCT. The tube/fork combo weighs in at 84 pounds, so be sure you can handle it. There also is a fairly heavy price tag: $5,600.
Regarding overall quality, that is impossible to judge from one example. The scope I used worked flawlessly despite having been dropped at another star party (the fork had the scars to prove it). A bit disturbingly, however, input from LX400 owners over the last couple of years indicates the scope has not been completely problem free. Quite a few buyers have had to return their LX400s to Meade for various problems, many involving the focus/collimation motors. Over the last year, Meade has been working hard to resolve the telescope's problems, stopping production for a while, and perhaps by the time this book goes to press the last bug will have been exterminated. Some owners have also expressed concern about the LX400's unsealed optical tube. Due to the fact that the corrector must move to focus, there is a gap between the tube and the lens, and dust, dirt, and insects can conceivably gain entry. While no serious problems have surfaced in this regard, it is clear that if something gets inside the tube, it will be hard to get it out. The corrector cannot be removed as easily by the user as that of a standard SCT.
Some astrophotographers have raised questions about the RCX drive's tracking quality. However, the scope's periodic error and general tracking accuracy appear to be at least as good as that of the LX200-ACF and perhaps somewhat better. That is, not as good as a GEM mount costing two or three times as much as the whole 10-inch RCX, but very good nevertheless. The LX200 in its various incarnations over the years has taken thousands of excellent deep sky images.
Should you buy an LX400-ACF? If you want a fork-mount telescope, the LX400 would be impossible to ignore. Meade uses the word advanced a lot in this CAT's advertising, and in this case, it is not hyperbole. This telescope really is a considerable advance over what has been available to the fork-mount SCT user previously. Also, despite the usual Internet rumors, Meade has a good record of satisfying its customers. The biggest problem with the LX400? Getting one. As this book goes to press, it appears Meade has chosen to suspend production of the LX400 telescopes (except for the top of the line 16- and 20-inch instruments) indefinitely.
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