StarPointer is a virtual electronic finderscope for astronomical telescopes.

StarPointer is a virtual electronic finderscope for astronomical telescopes. This device works with Stellarium and helps the observer identify objects in the sky.

Prototype version of the StarPointer sensor kit.

Prototype version of the StarPointer sensor kit.

This unit can be attached to the telescope without modifications and connects with the computer through the USB port. The StarPointer uses a few onboard sensors to determine its angle and position. After obtaining that information, the unit calculates the RA (right ascension ) and DEC (declination) coordinates of the telescope and transfers those details to the Stellarium.

The StarPointer builds around the STM32F103C8 microcontroller, ADXL345 3-axis accelerometer, and HMC5883L 3-axis magnetometer. This unit communicates with the PC using the inbuilt USB peripheral of the STM32F103C8 microcontroller. The firmware of the StarPointer is developed using the LibOpenCM3 library and built using GNU ARM Embedded Toolchain.

This unit can attach to any astronomical telescope or binocular regardless of its type or mount. After attaching the unit, the user needs to calibrate the StarPointer using the configuration software. This configuration software allows StarPointer to set the latitude and longitude of the observation location, RTC date/time, and RA and DEC offsets. After performing the above steps, the unit is ready to use with the Stellarium.

The StarPointer is designed to work with Stellarium's telescope control plugin. Its firmware has been developed to work with the Meade LX200 communication protocol, and no additional modifications are needed for Stellarium to work with this sensor kit.

Bottom side of the StarPointer sensor kit.

Bottom side of the StarPointer sensor kit.

When assembling the sensor module, we strongly recommended using the genuine STM32F103C8T6 MCU for this project. During the prototyping stages, we found a few counterfeit STM32F103C8T6 MCUs which are not working properly with this firmware. According to our observations, most of the counterfeit STM32F103C8T6 MCUs failed to initialize the RTC and USB peripherals at the startup.

We also design a suitable enclosure for this project, and its design files are available to download at tinkercad.com. This design can be 3D printed using either ABS or PLA. To get the optimal results, we recommended attaching this enclosure to the piggyback bracket of the telescope.

3D printed enclosure for the StarPointer PCB.

3D printed enclosure for the StarPointer PCB.

The PCBWay sponsored this project. PCBWay offers high-quality PCB manufacturing and assembling services. Also, they offer CNC and 3D printing services. The StarPointer PCB is available to order from PCBWay. The StarPointer enclosure can also order from the PCBWay 3D printing service. Check out the PCBWay website for their manufacturing capabilities and pricing.

StarPointer test setup with Celestron PowerSeeker 80EQ telescope.

StarPointer test setup with Celestron PowerSeeker 80EQ telescope.

StarPointer is an open hardware project. All design files, firmware/application source codes, and schematic files are available to download at the project GitHub repository. The complete documentation is also available in the wiki section of the GitHub repository.

Dilshan Jayakody
Embedded systems engineer, amateur radio operator, and amateur astronomer.