Black Sky Meter – a device for measuring the brightness of the night sky


Black Sky Meter (BSM) is device for measuring the brightness of the night sky in places of astronomical observations.

Black Sky Meter – this is an innovative product for the observer of the stars. Within seconds you can determine the brightness of the sky.

BSM Android app

Black Sky Meter (BSM) is device designed to measure the brightness of the night sky in places of astronomical observations.

BSM measures the brightness of the night sky in magnitude per square angular second (Mag / arcsec2).

Thanks to the use of the TAOS TSL237S sensor, BSM has unprecedented sensitivity!

BSM is made in the form of a key fob, which will allow it to be always at hand on observations.

BSM comes with a microUSB to UCB Type C adapter.

With BSM you can:

  • Find out how good the night is for astronomical observations.
  • Compare the brightness of the sky in different places.
  • Send a short message and save the result to E-mail.
  • Accumulate measured data on E-mail for statistics.
  • Determine the best night for observe the least bright objects in deep space.
  • Make maps of the night sky brightness for your area.


  • Vibro and beep during measurement.
  • Sky brightness is displayed in magnitude per square second of arc (Mag / arcsec2).
  • The infrared blocking filter provides measurement only in a visual bandwidth.
  • Indication temperature is in degrees Celsius (° C).
  • Location indication.
  • Thermo compensation of measured values.
  • Custom calibration.


  • The half maximum width (FWHM) of the angular sensitivity is ~ 35 °.
  • Accuracy of indications – 0.10 Mag / arcsec2
  • Interface – microUSB.
  • Android OS 4.3 or newer version.
  • Powered by the battery of a smartphone or tablet.
  • Body material – Aluminum (surface anodized)
  • Size – 50 x 16 x 16 mm
  • Weight – 40g
  • The maximum light sampling time is 90 seconds.
  • The developer reserves the right to change the design and specifications without notice.


The instrument is calibrated and ready for operation. Simply connect the device to the micro USB connector of your mobile device and click the “Start” button on the screen of the opened application. Further, within 5 seconds, lift the device above head level so that shadows or reflections from your body do not interfere the measurement, and aim the device at the zenith. The measurement process will be accompanied by sound signals with a period of 1 second. After some time, the display will shows the corresponding readings. Take several measurements to get a more accurate result. The measurement time is highly depend on the level of illumination in the area. Under the city sky, the readings appear almost instantly, while under a very dark sky (a moonless night far from civilization) the measurement process can take more than a minute. The maximum signal accumulation time is 90 s. During the accumulation of the signal, the screen backlight of the mobile device will be turned off to eliminate the influence of spurious reflections from surrounding objects. For the same reason, try to choose the right places to measure. Avoid any artificial light sources, including surfaces that reflect and scatter light.

BSM User manual

Before using BSM Android app please read the Privacy Policy for Black Sky Meter V4

In order to improve the quality of the product, the manufacturer reserves the right to make changes to the design and equipment without notifying users.

Successful observations and dark sky! Thank you for choosing Black Sky Meter.

Free shipping

Shipment within 5-7 business days after payment day.

Weight 0.08 kg


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