This is an application of the TSL 2591 sensor to measuring sky brightness for astronomical applications. It returns the sky brightness in units of magnitude per square arc-second. Also accessible to the user are the raw counts of the visible and IR channels.

• Adaptive exposure and gain control to reduce noise in low light environment.
• Calibration offset can be adjusted by user with setCalibrationOffset
• Noise estimates given assuming signal counts follow a Poisson process

• Emulator for SQM-LE network connected device compatible with ESP8266 devices
• Emulator for SQM-LU usb connected device compatible with most Arduino devices
• Simple example code for Arduino devices

This, along with other Arduino projects, can be placed on an ESP8266 module. I have written a library for using these modules to push data to an influx time-series database and display these results using Grafana. Below is a screenshot the Grafana frontend with of one night. Shown are two sensors, one in a Weather Station taking measurements from the sky, and another in a cabinet to illustrate the noise floor.