Steve Bedair's
Telescope Site
Gladewater , Texas
Updated 5-2004

Meade's 497 Autostar Controller

Meade 497 Autostar

    There’s not a whole lot you can say that hasn't already been said about the Autostar controller. Computer pointing technology along with a list of features and an extensive database that can be easily upgraded from the Internet makes the Autostar a first class controller. One feature that is not mentioned is the ability to easily change the Alt and AZ ratios in the Autostar.  The Alt and Az ratios are simply a set of numbers entered into the Autostar to determine the amount of movement needed to correctly position the worm gear that correctly positions the telescope. The ability to change these ratios in the Autostar allows the use of a wide range of worm gear sizes to be used in building a Go To mount.

 To Calculate new Alt / Az ratios for new worm gears


Using Meade DS Motors:

  All DS & ETX model telescopes use a 60 tooth worm gear and have an Alt / Az ratio of  1.36889
To calculate new ratios for the DS motors take the known ratio of 1.36889 and divide by 60.
This equals  0.022814833333333333333333333333333   This represents the ratio for one tooth on the worm gear.
Now multiply the 0.022814833333333333333333333333333  times the number of teeth on the
new worm gear to be used. ( These calculations were done using the calculator function on my computer )

Worm gear                                         multiply by                                      New Alt/Az Ratio

    60                        0.022814833333333333333333333333333                       1.36889
    96                        0.022814833333333333333333333333333                       2.19022
    120                      0.022814833333333333333333333333333                       2.73778
    144                      0.022814833333333333333333333333333                       3.28533
    180                      0.022814833333333333333333333333333                       4.10667
    200                      0.022814833333333333333333333333333                       4.56296

Using Meade LXD55 Motors

  All LXD model telescopes use 144 tooth worm gears and an Alt / Az ratio of 2.53715
To calculate new ratios for the LXD motors take the known ratio of 2.53715 divide by 144
equals 0.017619097222222222222222222222222
Now multiply the 0.017619097222222222222222222222222  times the number of teeth on the
new worm gear to be used. ( These calculations were done using the calculator function on my computer )

Worm gear                                         multiply by                                      New Alt/Az Ratio

    120                       0.017619097222222222222222222222222                       2.11429
    144                       0.017619097222222222222222222222222                       2.53715
    180                       0.017619097222222222222222222222222                       3.17143
    200                       0.017619097222222222222222222222222                       3.52381

Using Meade 114EQ/4504 Motors

  All Meade 114EQ / 4504 telescopes use 100 tooth worm gears and an Alt / Az ratio of 4.56296
To calculate new ratios for the 114EQ / 4504 motors take the known ratio of 4.56296 divide by 100
equals 0.0456296
Now multiply the 0.0456296  times the number of teeth on the
new worm gear to be used. ( These calculations were done using the calculator function on my computer )

Worm gear                         multiply by                           New Alt/Az Ratio

     96                                    0.0456296                                   4.38044
    100                                   0.0456296                                   4.56296
    120                                   0.0456296                                   5.47555
    144                                   0.0456296                                   6.57066
    180                                   0.0456296                                   8.21332

To change the Alt and Az ratios in the Autostar Controller

   Changing the Alt / Az ratios in the Autostar might seem confusing at first but is really a simple process. The Autostar is very user friendly and at any time a telescope model is selected from the Telescope Menu, the Autostar automatically resets all values back to the original factory settings. So there is no need to record the settings before changing them. After powering up the Autostar and getting past the time and date you will need to:
1. Select the Setup menu.

2. Select a Telescope Model in accordance to what motors are being used ( DS , LXD, 114EQ/4504 ).
If using DS motors you may select any DS or ETX model telescope. The only difference is that the DS models
are for Alt / Az fork mounts only and the ETX models allow you to polar align ( fork mount polar align )
If you are using an EQ mount you need to select the 114EQ / 4504 model to allow for an Equatorial Mount.
If the 114EQ / 4504 model does not show in the Telescope selection menu you will need to download a
"Patched Version" of the current Autostar software from Mike Weasners site:  click here
Look under "Patches (ASU 3.x ROM file)" for the most current patches. The patches are created by
Dick Seymour and will add the 114EQ / 4504 model telescope to your Autostar Menu.

3. Select  "Az Ratio" and with the numeric key pad of the Autostar controller enter your new ratio. Make sure the numbers are correct and press the Enter button.
4. Select " Alt. Ratio" and follow the same procedure as for the Az ratio.
    Note that once the new ratios are entered you can check the motor direction by pressing the arrow direction
    keys. When the up arrow is pressed the ota should start pointing up and the same for the left and right.
    If the direction is wrong you will need to change the + or - sign in front of the Alt or Az ratio.
    For example if the ratio is + 01.36889  change to -0136889 and this will reverse the direction of the
    affected axis.

5. Select Train Drive and follow this procedure.

 After this I usually turn off the power and restart the Autostar before performing an alignment. From now on each time the Autostar is powered up only the date and time have to be entered. The Alt / Az ratios will remain in the Autostar's memory.
There are a few exceptions that will affect the new information entered into the Autostar:

1.   If the Reset feature is selected the Autostar will reset everything back to the first
      time ever used mode.
2.   If a Telescope Model is selected and the enter key is pressed it will default back to the original Alt / Az ratios.
      If you do check the ratios to see if they are correct just press the mode key to escape.
      The new ratios will remain.

My Mount turns the wrong direction

If you are using the Meade LX 90 settings for your mount you will notice the Az axis slews the wrong direction. This
is caused by the fact that the LX 90's Az worm gear turns in the opposite direction of the DS and ETX series telescopes.
This can easily corrected by changing the + or -  at the beginning or the Az ratio. Use the direction key to highlight the
+ or - and then use the arrow key to change. The Alt axis is the same for all the models.
This also applies to any mount if the direction is wrong. Just change the + or - at the beginning of the ratio.

To use the Autostar with a German Equatorial Mount ( GEM )

Note: To use the Autostar controller with a GEM / EQ mount it will require a patch downloaded to the Autostar.
         The patch was developed be Dick Seymour and can be downloaded from Mike Weasners web site
          ( Click here ) . This allows the Autostar to show telescope model 4504 and 114eq  Equatorial Mounts.
          If the patch is not downloaded the Autostar it will show only DS and ETX models ( fork mounts )

Autostar Resources:

Meade's Autostar Download Site

Mike Weasners Autostar Information Site ( Information & Patches )

RoboScope Yahoo Newsgroup  ( Under the Files and Links section )

Autostar Wiring Diagram

Note:   The worm has no affect on the alt / az calculations
Only the tooth count of the larger worm gear.
( one revolution of of the worm shaft equals one tooth on the worm gear)


Comments or Questions

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 Copyright 2000 / 2004  Steve Bedair