SQM Toolbox

SQM Toolbox is a comprehensive macOS application for measuring, analysing and understanding night sky brightness using Unihedron Sky Quality Meter devices (SQM-LE, SQM-LU and SQM-LR). Whether you are an amateur astronomer, educator, dark-sky advocate or researcher, it provides everything needed to monitor light pollution and understand the natural night sky.

The app automatically collects measurements from connected SQM devices and works seamlessly with SQM Mobile on iPhone, allowing field measurements to be synchronised automatically via CloudKit. Measurements are collected continuously, averaged each minute, and organised into a consistent noon-to-noon record, making entire nights easy to compare. A rolling seven-day history is maintained, with support for importing archived datasets and sharing data between multiple systems.

Beyond basic measurements, SQM Toolbox provides a detailed physical understanding of the night sky. It calculates Sun and Moon elevation, twilight phases, and sky-brightness conversions including NELM, illumination and Bortle class. Advanced physical models estimate the natural night-sky background by calculating the contributions of moonlight, the Milky Way and airglow, making it possible to distinguish genuine light pollution from predictable natural changes in sky brightness. These models include the widely used Krisciunas & Schaefer (1991) model for moonlight, Milky Way brightness using the maps of Schlosser & Hovest (1998), and an empirical model of airglow brightness.

Powerful visualisation tools let you explore your data in detail. The table view presents complete minute-by-minute records, while the graph view displays entire nights with twilight shading, cloud overlays, multiple overlaid parameters and optional Moon and geophysical information. Almost every aspect of the display can be configured to suit your own observing and analysis requirements.

SQM Toolbox integrates with external cloud sensors through the widely used Clarity II data format (including devices such as the Lunatico CloudWatcher) and can also use data from Solo devices via their HTTP interface. Cloud measurements are incorporated directly into your analysis, making it easy to distinguish the effects of cloud cover from changes in sky brightness.

Comprehensive export and sharing options include CSV, JSON and Skyglow formats. The app supports automatic uploads to citizen-science projects, provides nightly statistics and "best ever" tracking, and makes it easy to build and maintain long-term archives of sky-brightness measurements.

Long-term analysis tools currently include Moon phase analysis and Unihedron-compatible filtering, with additional analytical tools already under development.

Whether monitoring a permanently installed observatory SQM, carrying out mobile surveys with SQM Mobile, or analysing years of archived observations, SQM Toolbox provides a complete environment for understanding the brightness of the night sky and the factors that influence it.

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**System Requirements:** macOS 15.0 or later.

SQM Toolbox is free to download and use indefinitely. The Free version provides everything needed for occasional use and works seamlessly with SQM Mobile.

A Premium subscription unlocks the complete feature set for enthusiasts, observatories and long-term monitoring projects. It is particularly well suited to permanently installed SQM systems while remaining fully compatible with handheld instruments.

Every Premium subscription begins with a one-month free trial—long enough to experience every phase of the Moon. You can cancel at any time during the trial without being charged.

SQM Toolbox Privacy Policy:
https://www.gerspatial.com/privacy-policy-for-sqm-toolbox

Standard Apple Terms of Use:
https://www.apple.com/legal/internet-services/itunes/dev/stdeula/