Tracking satellites with Meade ETX-90 EC

Dave Mullenix (
Tue, 23 Mar 1999 20:43:00 -0600

Meade has a new telescope out, the ETX-90 EC.  It's a cute little 90mm
scope on a battery operated motorized mount which sells for $595.00.  It
can also be used with Meade's new Autostar #497 computerized controller,
which lists at $149.95.  See for details.

This computerized controller is supposed to find and track satellites as
well as conventional astronomical objects like the moon, planets, stars,
etc.  Here's the page from the Autostar operator's manual, which can be
found on the above site:

"SATELLITE is a database of Earth-orbiting objects such as the
International Space Station, the Hubble Space Telescope, Iridium and
Global Positioning System satellites, and geosynchronous orbit
satellites. To use this option, choose an object from the Select menu,
then press ENTER. Autostar scans its database to find if that
satellite is expected to pass overhead within the next 6 hours. If
this is the case, use the scroll keys to access a list of information
about the pass, including acquisition time, location, etc. At the end
of the list is an alarm. Press ENTER and Autostar automatically sets
the alarm to sound several minutes before the scheduled appearance.
Return to regular observations until the alarm goes off. At that time
follow this procedure:

  1. Return to the Satellite menu and select the satellite.
  2. When the desired satellite is on the top line of the display,
     press GO TO. Autostar slews the telescope to where the satellite
     should appear. The motor drive stops and a countdown starts.

     NOTE: If the scheduled appearance point of the satellite is
     obstructed (i.e., a building, tree, or hill), press ENTER and
     Autostar starts to move the telescope along the expected
     satellite track. When the track clears the obstruction, press
     ENTER again to pause the telescope, then continue with this

  3. With about 20 seconds left on the countdown timer, start watching
     through the telescope viewfinder for the satellite to enter the
     field of view.
  4. When the satellite enters the viewfinder field of view, press
     ENTER. The telescope starts to track with the satellite.
  5. Use the Autostar arrow keys to center the object in the
     viewfinder, then look through the eyepiece to view the object.

"Satellite orbits change and new satellites (including the Space
Shuttle) are launched. Visit the Meade web site (
approximately once a month to get updated information and instructions
on how to download these data to Autostar. If using orbital parameters
that are more than one month old, the satellite pass may not happen at
the time predicted by Autostar. To download new satellite data into
Autostar memory requires the optional #505 Connector Cable Set (see

"NOTE: Satellite observing is an exciting challenge. Most satellites
are in low orbit, travelling at approximately 17,500 mph. When
visible, they move quickly across the sky and are only in the field of
view for a few minutes, requiring Autostar to slew the telescope
rapidly. Best viewing is near sunrise or sunset when the sky is still
dark. Viewing in the middle of the night can be problematic since the
satellite may pass overhead, but not be visible since it is in the
Earth's shadow.

I've just purchased the combination, but it doesn't come with a cable to
connect the computer to the PC, nor has Meade published instructions on
downloading orbital elements.  It comes with a few orbital elements
already in place, so I'm going to try it on some GPS birds as soon as we
have a suitable night.  I don't know how old these elements are, but I
figure the GPS orbits are stable enough so that even 3 month old
elements should work.  Has anybody yet successfully tracked a satellite
with the ETX-90 EC / Autostar combo?  Any info on downloading new

Dave Mullenix