If you're like me, you keep asking the same question: "Why can't I talk to my toys with my PDA?" In this case, my "toy" is a Meade ETX-105 Maksutov-Cassegrain telescope.

The ETX-105 is a very cool, somewhat affordable high-resolution telescope with auto-tracking capability. This auto-tracking stuff sounds great, but to unleash its full potential you need to add another Meade option called Autostar. The addition of the Meade Autostar system turns your Meade telescope into an automatic celestial-object-locating system.

Autostar brings a very important feature into this system: an open-standard RS232 serial interface. Meade provides a detailed protocol specification so geeks like us can "kick it up a notch" with this interface port.

Now for the good stuff. If I have an RS232 port and all the info needed to control this port, what must I build to allow any handheld -- or PC running any OS -- to talk to my telescope?

Interplanetary PDA

There are a few things built into nearly every PC and handheld that I can use to pull off the feat.

• I see lots of IrDA (infrared data) ports.
• Just about every PC speaks TCP/IP.

What if we build a TCP/IP-to-Autostar RS232 bridge that can also talk over an IrDA link? This would allow us to control our Meade telescope with the Autostar, any Palm IrDA device, or any PC running a Web browser, even over an 802.11 or Bluetooth wireless option.

Even better, this also lets us control our telescope over the Internet. Bam!

Steven Pope is a fellow at ZiLog. He holds five U.S. patents, with a focus on embedded microcontroller hardware and software applications.
What you'll need

To control the Meade Autostar using a Palm or 802.11 iPaq handheld, or a Macintosh, PC, or Linux box, here's what you need.

• Meade Telescope with Autostar controller
• ZiLog Acclaim F91 Development Kit loaded with the ZTP_1_2_Galileo hex file
• PalmPilot PDA with IrDA loaded with the Galileo.prc file
• Any device with an Internet browser
• A clear night sky

Be sure to check the ZiLog site after my segment on the show. We'll post links to download the ZTP_1_2_Galileo hex and Galileo.prc files in case you want to tackle the telescope mod yourself.

Building the rig

Here's the rough idea on how I put together all the hardware and software components. To see my PDA-powered telescope in action, and to learn the details on how I did it, watch tonight's episode of "The Screen Savers."

• I put together the TCP/IP-and-IrDA-to-RS232 bridge using the ZiLog eZ80F91 Ethernet/IrDA module and lots of software.
  
  
• It wasn't hard to find parts for this mod. I mounted the module in a clear plastic box that attaches to the telescope's tripod (see images below). I got the box from a local TAP Plastics store, and from RadioShack I got the parts for the interface cable from the module to the Autostar.
  
  
  
  
• Here's the complete list of parts for the telescope mod.
  
  • RadioShack DC Power jack (part number 274-583)
  • RadioShack mini plug-input jack (part number 274-284)
  • 12-foot RadioShack black phone cord (part number 279-466)
  • RadioShack mini jack plug (part number 274-249)
  • RadioShack DC plug (part number 274-573)
  • 3-inch by 4-inch clear plastic box from Tap Plastics
  • ZiLog F91 Development Kit with Zilog ZDS application
  
  
  
• In addition to the parts listed, I also added a small 3-D Trimble GPS module to my design. The GPS module helps me get two of the most important parameters: my position and the time of day. This data, along with the date, is passed up to the Autostar system and gives the telescope a point of reference.
  
  
• All told, the mod cost about $200, covering the GPS module, Ethernet/IrDA module, plastic box, cables, and small power supply. The $200 doesn't include the cost of my telescope with the Meade Autostar system ($795).

Green lasers: Very cool star flashlights

As you'll see in the segment, my telescope is equipped with a green laser pointer. A green laser beam is significantly brighter than a red laser beam. Because of its unusual color, it's also much more noticeable.

The wavelength of the green laser is 532 nanometers, versus 650 nanometers for a red laser. Unlike a red laser, you can see a green beam in midair when it's really dark -- not just the laser beam dot itself, but a green ray of light.

You can also see the green laser beam dot at much greater distances than a red laser dot. The brighter beam and the distance at which it is visible let you use the green laser to point out star constellations.

See the stars

Here's a picture of the Orion Nebula (M42) and NGC 1977 taken with a Meade 7-inch 178ED telescope.



Fun facts about telescopes

• It isn't certain who constructed the first telescope, but a Dutch spectacle-maker, Hans Lippershey, is given credit. Lippershey introduced his telescope in 1608, and news of this instrument, which made "seeing faraway things as though nearby," spread rapidly through Europe. By the fall of 1609 telescopes could be purchased in some European spectacle-maker's shops.
  
  
• Galileo, an Italian astronomer and physicist (1564-1642), constructed his first 3x telescopes in the summer of 1609. He continued making telescopes with more power. In the fall of 1609, using a 20x telescope, he observed lunar mountains, stars in the Milky Way, and Jupiter's moons. These observations, published in March 1610, were questioned by other scientists, who didn't have telescopes with as much power. Galileo's lead in astronomy was short-lived. Within about six months others had telescopes of equal or better power.
  
  
• Sidereal time, or star time, is four minutes slower then solar time.