Connecting a Telescope to Planetarium via Serial Port

(Connecting via Bluetooth is described here)

To connect the Telescope via serial port you need the following:

• Handheld with serial port
• Serial cable for the handheld
• Serial cable for the telescope
• Perhaps a null modem and a gender changer
• Serial telescope driver

PalmOS devices with serial Port

• Treo 600, Treo 300, Treo 270, and Treo 90
• Tungsten C, T, T2, T3, W, Zire 71,
• Garmin iQue 3600
• Palm m500, m505, m515, m125, m130, i705,
• Palm m100 and m105.
• Palm V series
• Palm III series (includes Palm VII, PalmPilot, Handera/TRGPro, Symbol SPT1500)
• Sony Clie TH, T, TJ, TG, NX, NR, SJ, and SL series
• Visor Solo, Deluxe, Prism, Platinum, Neo, Pro, Edge

Serial cables and connection

For the handheld do not just buy a serial Hotsync cable! This might work well with the PC, but not with the telescope. The reason is that many Palm devices have serial ports with digital voltage levels only. They need level converters to bring the signals to proper RS232 levels, and these are usually built into the serial cable. But they need power, and Hotsync cables usually take this power from the PC side (from the RTS signal for example). This makes sense to save the Battery of the handheld. However, when connecting to the telescope we only have three lines. There is no RTS or similar signal where the level converters could take their power. So what you need is a cable that takes the power for the level converter electronics from the PDA side.

Very old Palms have the level converters built into the device, and a serial hotsync cable or cradle will work well for them.

Connection:

To connect to the handheld you need a serial cable for your telescope. This is a standard accessory that is intended to connect the telescope directly with the PC or Laptop. To get such a cable contact your telescope dealer.

The null modem crosses the serial data lines, so that the telescope and the handheld do not both talk on the same line while listening on the other.

The gender changer is needed to let you plug the two female cables together.

Serial telescope driver

The following telescope drivers are available:

Download the appropriate file and install it on your Palm.

Please note: You need an AutoStar or Hand Controller device! You must not connect the Telescope directly to the Palm without the AutoStar or Hand Controller in between, this might damage your Palm or the telescope.

Here is some information from a user who tested various Meade and Celestron telescope configurations.

Usage

If the telescope driver is installed properly, the telescope button shows up in the sky view tool bar. Tapping this button opens a popup menu with the available functions.

• Query Position - Asks the telescope where it is pointing at and displays a symbol in the sky map.
• Set position - Only available if you have a Goto telescope and if you have selected an object in the sky map. Commands the telescope to that object.

Trouble shooting

The "Serial port communication error" appears when Planetarium does not receive back any data from the telescope. There are several possible reasons for this situation:

1. Wrong cable (try inserting/removing a null modem). Is it a cable that is powered from the device side, not from the PC (telescope) side?
2. Broken cable
3. Broken serial port in the Palm
4. Broken serial port in the telescope
5. Telescope not in the correct mode to receive commands through the serial port.

Most probably it is the first one.

You can rule out the last two items if you can control the telescope from the PC.

To rule out items 2 and 3, you could try to connect the Palm to the PC and make a Hotsync via the serial cable. You will have to set the Hotsync manager on the desktop accordingly and change some settings on the Palm as well. (Note that if you need a null modem for connecting to the PC, you don't need one for connecting to the telescope, and vice versa. ) If you can make a hotsync, the cable is working and the handheld as well. However, it might still be the wrong cable (e.g. when it takes its power from the PC, not the Palm.)