Bruce L. Gary, Hereford Arizona Observatory


If every user of a Meade RCX400 telescope became as frustrated as I did seeking guidance from the Meade RCX400 Instruction Manual, due mostly to omissions, then this "User Tips" web page might reduce some of the frustration. It is written by an amateur with no connection to Meade, and it endeavors to provide a temporary solution to the need for an updated, good quality Instruction Manual.

I assume that most owners of an RCX telescope are serious amateurs, not the "eyepiece-using Wow!" kind. Therefore I assume that anyone reading this web page has a CCD camera attached to their RCX. I will further assume for some of the entries that the advanced user wants to control the telescope and camera with their favorite software, which in my case is MaxIm DL. This means they'll be using Ajai Sehgal's ACSOM telescope driver, which is now available as a beta version 4.2.6. Ajai has agreed to review those parts of my web page pertaining to the use of his driver.

Some of the tips that follow are RCX telescope specific and will be helpful to all users, while some are specific to the control of an RCX with MaxIm DL. I'll even include a few items of possible general interest for users of any good quality telescope. I'm open to requests for the coverage of other material.

Links internal to this web page

  RCX Unique Features
    Terminology, appearance of window and assumptions
    Polar alignment
    Star alignment
    RCX driver setup
    Parking and unparking
    RCX driver set-up
    Dew heater control

  Other Features of General Usefulness
    AO-7 image stabilizing
    Move window  manual nudging
    MaxPoint pointing refinement
    Lightning precautions
    Baffled (not what you're thinking)

Terminology, Appearance of Windows and Assumptions

RCX = any of the Meade RCX400 telescopes
MDL = MaxIm DL
RCX driver = Ajai Sehgal's ASCOM telescope driver, currently version 4.2.6 (Beta 6)
AutoStar II = Autostar II = various ways of referring to the "virtual AutoStar II window" (also referred to as "Keypad" by the RCX Control window

MDL telescope control window

Figure 1. MDL's "Telescope Control" window. It's configured for controlling the telescope through the pointing refining program MaxPoint (analogous to T-Point). If you're not using MaxPoint then the telescope selection will be "Meade RCX Telescope and Focuser."

RCX driver set-up

Figure 2. "RCX Setup" window.

RCX driver window

Figure 3.
"RCX Control" window for use of Ajai Sehgal's ASCOM telescope driver.

Autostar II virtual handbox window

Figure 4. Autostar II virtual handbox window (also referred to as "Keypad" by the RCX Control window).


The following assumes that you're using an equatorial wedge (or super-wedge), that your telescope is permanently mounted (no portable use), and that you have a CCD camera attached to the telscope. These assumptions should be safe because the only reason to spend so much money for a telescope like the RCX is if you intend to do serious work with it. With apologies to those "down under" I'm also assuming for some items that you're in the northern hemisphere. I'm going to assume that no one intends to use Autostar Suite for controlling the telescope; that program is meant for newbies and newbies don't spend extra money to buy a telescope with features that only advanced amateurs will appreciate. You can control the telescope with TheSky6 or MDL (MaxIm DL), and probably other programs. I'm going to assume you're using MDL, and if you're using another program then just make the necessary functional equivalence translation from my description.

I'll use italicized font for messages from the AutoStar II program. The manual doesn't mention that the program AutoStar II resides on a chip located in the Meade mounting base, and that it is merely asccessed via the AutoStar II handbox controller. Navigating the Autostar II menu structure will be shown using "/" to separate levels, as in Utilities/ParkScope (even though the message is Park Scope I join the two words).

Finally, I'm assuming that you've upgraded to AutoStar II, version 2.1b or 2.1c. Version 2.0e won't work with the Ajai Sehgal's ASCOM telescope driver, and this driver is necessary for some of the things described below. If you try upgrading according to instructions in the manual, good luck. I couldn't, and the problem was partly due to lousy instructions in the Meade Manual.

RCX Unique Features

Polar Alignment

One of the first things to do with a new telescope is a polar axis alignment. There's nothing different about doing this with an RCX but since Meade's Instruction Manual fell short on describing the best way to achieve a good polar axis alignment I'm going to include my favorite procedure here. I like the "Declination drift" method for adjusting both the polar azis elevation angle (tilt) and azimuth. All manuals seem to imply that it's difficult, but it's not. Once you have an approximate setting use either an eyepiece or CCD camera for the following.

Point to a star near the meridian and celestial equator. Determine whether it drifts in Dec to the north or south. If the star drifts north your axis is west of true north and should be moved eastward (turn the east knob clockwise).

Point to the east, about 20 degrees above the horizon, and again determine if stars drift north or south. If the drift north then the axis is pointed above the true celestial pole, so you have to lower it (???). As an alternative you can look west and reverse the response to drift direction.

Using an eyepiece can yield accuracies of ~0.5 degree. Using a CCD camera can lead to 0.1 degree accuracy or better. CCD images can readily be converted to quantitative drift rate measurements; this assumes you know the CCD's "plate scale" ["arc/pixel]. For example, looking east with a drift rate of +15 "arc/minute means you have a 1 degree error in axis tilt to correct. I use a digital inclinometer to make the appropriate adjustment, which removes some of the trial and error tedium of the process.

Star Alignment

Assuming, again, that you have a wedge or super-wedge, the easiest way to achieve a star alignment is to perform what the Meade manual calls a "Polar Align" (described in an appendix, as if most owners of the RCX will be alt-az users; this baffles me). Using the hand controller manually slew to the meridian, then slew north to approximately the north celestial pole. Navigate the menu structure to Setup/Align/OneStar and press Enter. Wait for the silly searching for Polaris and when it asks you to adjust the mount ignore that instruction and simply press Enter. We're "humoring" the Autostar program because we know better; we know that our mount has been adjusted to within 0.1 degree and their silly idea about adjusting the mount at this stage would ruin our polar alignment work. After we've pretended to adjust the mount and pressed Enter the Autostar will slew to a star and ask us to center it using the finder and eyepiece. It's optional to actually do this, but there's no harm done if you do. This actually achieves a small improvement but if you're planning on refining pointing using either T-Point or MaxPoint it really doesn't matter.

In theory this is the last time you'll have to do a star alignment. From now on you'll use Park Scope at shut down, and this will preserve the star alignment information for the next observing session.

PEC Training

If you're going to use an image stabilizer, like SBIG's AO-7, or use an autoguider chip for nudging the telescope, then PEC training is optional. I spent a half hour doing a crude training and I don't think I improved anything. If you're going to work without an image stabilizer, or autoguider, then read the Meade manual and follow directions for RA PEC training. You can neglect Dec PEC training.

Sehgal's Driver Setup

Assuming you're using AutoStar II, version 2.1b or higher, you'll be able to use Ajai Sehgal's ASCOM telescope driver, also referred to here as the RCX driver. This will allow you to control the telescope using all the RCX unique features, such as collimation, dew heater, mirror fan, park, etc. If you don't have this driver because your AutoStar II version is too low, good luck trying to drive the telescope by pretending it's a "Meade LX200 and Autostar." Some things work, but why have this great telescope when you can't use its unique features?

Upon first use of Ajai's driver you need to go through a setup. Select the COM port, enter your site coordinates, and specify that you're using an equatorial mount. The other itmes are optional. Click "Apply" and "OK."

If you know where you want to "stow" the telescope at the end of each observing session you can enter values in the "Park Control" section.  Even though you've selected "Simple Equatorial" in the Mount Setup section, you should enter your park position in Alt-Az coordinates. If you intend to always park (stow) at this location then check the option "Slew to ALT-AZ Before Park." See the next section for details.

Parking and Unparking

After a good polar alignment, and a successful star alignment, you can save yourself from ever having to do another alignment for the rest of your life (a slight exaggeration) by "parking" the telescope before you turn off power. Ignore everyting in the Meade Instruction Manual about this subject; it's not only confusing, it's also wrong. Here's what you do.

Setting a Park Position

When you're done for the night, manually slew to what we'll call a "park position" (see the alternative park procedure usng Ajai's RCX driver, after this paragraph). Your park position doesn't have to be the same every night, but you'll probably settle on a favorite approximate position. Mine is pointing at the south horizon, because that allows me to move the sliding roof without decapitating the telescope. After slewing to a park position use the hand controller to Utilities/ParkScope. Depress Enter, and note the message "Turn power off now." If it "complains" about being below the horizon, or something similar, ignore the message. OK, turn the Meade power switch to off.

As an alternative to the park procedure described in the previous paragraph, you may use the park command feature of Ajai's RCX driver. To use this feature you need to setup a desired park position. This can be done in two ways: 1) Manually slew to a desired park position (stow position), then on the "RCX Control" window click the "Park Alt Az" button, click Apply, 2) open the Setup window from the "RCX Control" window and enter values for "Park Altitude" and "Park Azimuth" (don't worry about the fact that the "Mount Setup" section has you configured as "Simple Equatorial," Ajai takes that into account when you specify park azimuth and altitude).Click OK. This setuip only has to be done once. From then on, at the end of an observing session, you can command the telescope to slew to the designated park position using the "RCX Control" window's "Park" button.


When you start the next observing session simply turn on the Meade power switch and wait. The scope will spend about a minute moving slowly westaward in hour angle doing what it calls "Initializing... Smart Drive." Then it does a "GPS Fix."  Finally, the controls are given to you with "Select Item/Object" mode. You should have exactly the same star pointing coefficients as were in use when you parked at the end of the previous observing session. You're now ready to point to zenith for taking those flat fields before it gets dark.

[Note1:  When you use RCX Control's "Set Park Alt Az" you're not done; you have to go to the Setup window and check the box for "Slew to ALT-AZ Before Park." Otherwise, on the RCX Control window when you click "Park" it will use the current Alt-Az for a park position.I need to verify this. ]

[Note2: If you control the RCX telescope through MaxPoint, whenever you update the MaxPoint calibration I think the Park command saves those updated MaxPOint calibrations. I need to verify that.]


You have a choice of focusing "absolute" or focusing "relative." You may think that "absolute" is a good idea, but it's not, at least if you're using MDL.

To focus "absolute" you would have to select from MDL's Telescope Control window: "Setup" tab, "Focuser" section, "Connect" button. DON"T do that! It will cause the RCX focus motors to drive to a limit and wait for you to figure out that you've lost all knowledge of where a good focus can be found. Sure, the numbers displayed on Ajai's focus panel will be there to help you, but that means knowing what absolute values you want and then driving the focuser to that region, and performing a whole new focus routine. Why go to that trouble when you probably don't have to refocus anyway.

Here's my suggestion. Ignore the MDL Telescope Control's Focus connection and just go about your business until you're near the ROI (region of interest) and to verify or adjust focus. When you want to adjust the focus, note the present setting on Ajai's driver window.

For exampl,e it may show +3.407. Set the focus rate to "S.Fine" and click on either "In" or "Out" for about a second. When going "In" the focus readings will go in the postive direction (seems opposite to me, but that's what happens). For my RCX there's a little hysteresis, so it may take 2 or 3 brief adjustments before the focus readings move in the expected direction. Focus reading changes of 0.010 matter.

Here's a consideration for focusing that applies to all telescopes: The atmosphere changes, so take several readings at a given setting and record (or at least note) the best one. Change the focus and repeat. I sometimes make a graph of these numbers versus focus setting reading (on the observing log). Good focus leads to good FWHM, which means "deeper" images (greater limiting magnitude).

As an alternative you can focus using the virtual Autostar II handbox (click the "Show Keypad" button on Ajai's driver window if the Autostar II window is not displayed).


This may be the reason you bought the RCX. It's easy! And it's important to always be in good collimation. Only with good collimation can you get sharp images, with good FWHM - and that translates to going deeper (i.e., a better limiting magnitude). With the Celestron telescopes it's difficult to collimate with just one person, but with the RCX one person can adjust collimation without even being close to the telescope. When I collimate I do it from the comfort of my home office, through buried cable communications.

The first step for collimating is to defocus enough that a CCD image of a star (near the center of the image) appears as a donut. If the donut is symmetrical, with no bright spot around the donut annulus, then you're in good collimation, as in this image.

But when collimation is bad the "hole" is offset from the center and the bright "donut" annulus is narrower at one clock angle. Suppose the narrowest part is at the 3 o'clock position. This will produce a bright spot at the 3 o'clock position, shown here.

The collimation adjustment that we want does two things: it moves the location of the star away from the bright spot clock position (i.e, in the 9 o'clock direction), and it reduces the intensity of the bright spot (because the width of the donut annulus become more uniform). To make an adjustment bring up Ajai's driver window and check the "Collimation Mode" check box. ALso check the "Always On Top" check box. In the "Motion Control" section click and hold for maybe 4 seconds the "E" button. Note whether the star moves in the desired direction. If it doesn't try the "W" button. If the star gets close to the edge then nudge the pointing in the desired direction (see the "nudging" paragraph in this item, below). Continue these adjustments until the donut is symmetrical and no bright spotsd are preswnt. If the "atmospheric seeing" is bad you may need to take several CCD exposures to be sure of the donut's appearance. When you're satisfied, uncheck the "Collimate Mode" check box.

Nudging the telescope can be done several ways. The easiest is to use the virtual Autostar II handbox. To bring that box into view, go to the RCX driver window and locate the button labeled "Show Keypad" (lower-right corner). If it displays "Hide Keypad" then the virtual Autostar II handbox is already open and you have to Alt-Tab your way to it. When that window comes up treat it as if it's a real handbox controller to achieve pointing adjustments.

Dew Heater Control

When the air is humid you can prevent dew accumulation on the corrector plate by going to Ajai's driver window and checking the "Dew Heater" box. You have to also set a heating level to something greater than zero, such as 20 %. The "Corr. Delta-T degC" value should be set to +2 C. This is how much warmer the corrector plate will be kept above ambient (hopefully ambient is measured well). The color status bar indicates the temperatre of the corrector plate in relation to ambient: grenn when they're the same, blue when the corrector plate is colder (dangerous when it's humid), and red/orange when the corrector plate is warmer than ambient. When you're concerned about corrector plate fogging up keep the color bar red/orange.

Other Features of General Usefulness

AO-7 Image Stabilization

Not everyone needs a tip/tilt image stabilizer, like SBIG's AO-7, or their new model AO-L for the large format CCD chips (the STL series). But I do, because my observatory is located next to mountain canyons that are the source of troublesome down slope winds. These winds begin about an hour after sunset and when they pass over my site they cause the star field to oscillate back and forth in one direction with amplitudes that are typically 10 to 20 "arc, sometimes 1' arc, and with periods that are typically less than a second. This lasts for ~20 minutes, and appear about once per hour. Fortunately, they subside in severity at about midnight. Because of this problem I need a fast-reacting tip/tilt image stabilizer, and the SBIG AO-7 is the perfect solution.

Whenever I physically rotate the AO-7/CFW/CCD assembly (in order to have a bright star available for the autoguider for the night's target) the image flip and rotate settings have to be changed, and the AO-7 drive motors have to be recalibrated. Also, after such a rotation I have to use a different "cheat sheet" posted next to my monitor that shows a map of which move commands are needed for the 4 move directions (e.g., -X = GoEast, etc). This extra work is worth it because on most nights I can't observe without the AO-7.

Move Window Nudging

I really like having the ability of nudging the telescope in very small increments. This is needed when I want to position the star field to within a few pixels of some preferred location (which is important for precision light curve observations). You can try doing this with the MDL "TelescopeControl/Telescope" window by specifying a few seconds of arc motion in the desired direction, but sometimes funny things happen when you do this (related, I think, to MaxPoint's use of a flawed set of pointing coefficients). The procedure I'll suggest is robust - it always works in the expected manner.

MDL's CCD control window, called "Maxim CCD," has a "Guide" tab. Click it, then click "Options," then click "Move." This opens a window where you can specify the duration of a move command and direction assignments (consult the MDL manual for more information about this). While observing I leave the left part of this window conveniently open, positioned on the right edge of the MDL work area. When I'm trying to place a specific guide star in a certain location on the autoguider chip (such as one corner) the move commands in this Move window are just what's needed. Also, if I'm using the AO-7 image stabilizer and thin clouds appear during an exposure and decrease the brightness of the autoguide star so that I can see that the star is drifting close to an edge of the AO-7 image window, I can use the Move window move commands to center the star.

Lightning Precautions

Lst year a nearby lightning strike damaged components at each end of the 100-foot cables that connect the telescope to my home office computer. I surmize that during the lightning strike a large voltage was presnet that caused electrons to rush to one end of the cables, and as they piled up they heated the components (a USB extender unit and a Celestron hand controller). Then the sign of the lightning's voltage changes, and electrons rushed to the other end of the cables, again over-heating the components at that end (the other USB extender unit and a serial I/O card). This happened even though nothing was turned on. My mistake was to leave the cables connected. I now have the practice (during the monsoon season, yes, we have monsoions in Southern Arizona) of disconnecting both cables control cables, at both ends.

Then there's the issue of lightning striking the telescope. Mine is in a sliding roof observatory, with only a canvas between the telescope and the sky. Lightning rods? People living in the mid-west know about them, but you can't find anyone who's ever heard of "lightning rod" in Arizona. I'm wary of inviting lightning to my neighborhood, by installing tall pipes nearby. That probably is safe, since at Flagstaff the Naval Observatory uses two such poles at the north end of a roll-off roof. If you have a dome, then it will protect your telescope from lightning (but not the cables).


The RCX has good baffling. That's not what this section is about.

I'm baffled by the neglectful way manuals are produced. Not just Meade, but also Celestron and just about any company in business today. It didn't used to be this way. In the "good old day" Hewlett-Packard produced good manuals. Even Microsoft used to produce good manuals. A software company president once told me that the the major cost of his product was not development, it was customer support. Now, if Meade and Celestron want to reduce their customer support costs they could produce good manuals. Let me rephrase that: If Meade and Celestron want to avoid the cost of upgrading CS, which is sorely needed (especially for the RCX), then they could invest in a good manual. A good manual should make good business sense: you'd have happier customers, word of mouth new sales, and a reduced CSbudget - win, win, win!

If Meade wants to use any of the material on this web page, please do! No charge! I've prepared it out of sympathy for people like me who spent good money buying a good telescope but left floundering on how to use it to best advantage. It just baffled me that Meade would design one of the best-ever telescopes, aimed at advanced observers, then neglect to describe how to use all its features.

I'm beginning to conclude the following:

    RCX users, we're on our own!

You can help by sharing your ideas for improving this alternative manual by e-mailing: B L G A R Y @ u m i c h . e d u


This site opened:  September 12, 2006 Last Update:  September 13, 2006