Dave Ek's Digital Setting Circles Project Home Page

Disclaimer: Use the information on these web pages at your own risk. While I have tried to make the instructions as complete and error-free as possible, I will assume no risk for and will not be held liable for damages of any sort which result from your attempt to use this information. Your use of this information constitutes acceptance of this policy. There is always the risk when constructing electronic circuits that a mistake will result in damage to one or more components. Since this project also involves connecting the circuit to a PC, there is the added risk of damage to the PC if the circuit is built incorrectly. If you are inexperienced in electronic circuit construction, seek the help of someone who is knowledgeable.

Welcome to the home page for my Digital Setting Circles project! Here you will find a complete description of the project, and information on how to purchase a PC board and programmed microcontroller chip. If you have questions about building this project, don't guess--contact me if you need help.

My digital setting circles project consists of an electronic interface which allows a PC to determine which direction your astronomical telescope is pointing. It connects to rotary encoders which you've mounted on your telescope axes to sense when the telescope is moved, and it communicates this information to a PC via a serial port. Software on the PC then takes that information and uses some mathematics to determine where (in celestial coordinates) the telescope is pointing. In summary, digital setting circles are high-precision pointing aids for astonomical telescopes--like regular setting circles, except much more accurate.


I spent considerable time and resources developing this project, and I continue to spend a fair amount of time answering emails and providing support to builders. This I do without any monetary compensation--I don't make a dime off the sales of circuit boards and chips for this project. If you've found this project to have enhanced your amateur astronomy activities, please consider tossing a few bucks my way in appreciation. Just click the "Make a Donation" button below to donate using Paypal or a credit card.

Project description

Frequently-Asked Questions

Obtaining a PC board and programmed microcontroller chip

How to build the interface

Software compatibility

Links to Related DSC Pages

Latest News!

New Version of my DSC Windows Software and ASCOM driver

I updated my DSC Windows and ASCOM driver software so that COM ports 5 through 8 are also available for selection. Hopefully this will help out those of you using notebooks with USB-to-serial converters. I also added a few southern hemisphere alignment stars (Achernar, Alpha Centauri, and Canopus). Let me know if you have troubles with this version. Go to the software compatibility page for details.

New Firmware Version

The firmware for this project is now at version 2.00. Several changes were made to the original version:

Chips ordered from FAR Circuits after 1 December 2003 should have the latest firmware. You can order a replacement chip from FAR Circuits if you'd like to upgrade to the latest version (or you can reprogram your existing chip if you know how to do so). If you're not sure if you have the latest version, connect your interface to your PC and fire up Hyperterminal. Set up Hyperterminal for 9600 baud, 8 bits, 1 stop bit, no parity, and no flow control. Then connect power to your interface. If you see "V2.00" appear on the screen, you have the latest version. If not, press Q. If you see an output that looks like "+00000 +00000" (but maybe with different numbers), you have the original version. If you don't see anything after pressing Q, you don't have Hyperterminal configured correctly, or your board is either not connected or not working properly.

Last site update: 2 Sept 2006