Sky Quality Meter by Unihedron: A Digital Window into Your Sky’s Darkness

Reviews

30 Jun

*Unihedron’s Sky Quality Meter – LU (SQM-LU), designed by Dr. Doug Welch and Anthony Tekatch*

In a hobby where precision matters, measuring the sky’s brightness can be just as critical as polar alignment or camera gain settings. That’s where Unihedron’s Sky Quality Meter – LU (SQM-LU) comes into play. Designed to offer real-time readings of sky brightness, the SQM-LU provides astrophotographers and observatory owners with a reliable way to quantify sky conditions, every single night. We used the LU model for this review.

What Is a Sky Quality Meter?

The Sky Quality Meter (SQM) is a sky brightness monitor that provides real-time measurements of the night sky’s luminance in magnitudes per square arcsecond. It features a narrow field of view, ideal for astrophotographers aiming to measure the zenith sky brightness without contamination from local light sources.

What makes the LU version particularly compelling is its USB interface. It connects directly to your PC and allows for continuous logging of sky quality throughout the night. This data can be stored and analysed to monitor trends, evaluate imaging conditions, and even contribute to global light pollution studies.

ASCOM Compatibility & Integration with NINA

One standout feature of the SQM-LU is its ASCOM compatibility. This means it integrates smoothly into software ecosystems like NINA (Nighttime Imaging ‘N’ Astronomy), allowing astrophotographers to register real-time sky brightness data into image metadata. Every photo you capture can now carry not only name, date, exposure and camera settings but also an accurate reading of the sky’s darkness at the time of capture.

*Sky Quality Meter - LU can communicate with NINA seamlessly thanks to its ASCOM compatibility.*

*The Sky Quality measurements in the name of each sub.*

For those imaging over many hours, this offers a valuable layer of insight. If sky conditions degrade (whether due to moonlight, high clouds, or urban lighting) this shift is reflected in the brightness readings, making post-processing decisions far more informed.

Sky Quality Meter Software & Contributing to Research

*SQM Reader Software comes in two Free and Paid versions.*

To complement its hardware, Unihedron offers the SQM Reader Software, which allows users to:

Log and export real-time sky brightness readings.
View brightness trends over the course of an imaging session.
Share and contribute data to light pollution mapping projects.

The Pro version of the SQM Reader which retails at 50USD (£47) allows more features such as time-averages readings, displaying moon phase and altitude at time of reading, and storing your sky quality data.

Why Use a Sky Quality Meter?

Data-Driven Imaging Decisions: Knowing when your sky is dark enough to start narrowband exposures, or when to pause due to encroaching light pollution, can save hours of wasted effort.
Long-Term Site Evaluation: Planning to build an observatory or visit a remote dark-sky site? The Sky Quality Meter helps you compare locations with hard data.
Metadata for Every Exposure: Embedded readings can help during post-processing to identify and discard frames captured under suboptimal conditions.
Global Contribution: Help track how skies change over time by submitting your logged readings to international databases.

Comparison to Other Unihedron SQM Models

  
      Model
      Interface
      Field of View
      Key Feature
    

  
      SQM-LU
      USB
      20°
      Real-time PC logging, ASCOM compatible
    

      SQM-LU-DL
      USB + Data Logger
      20°
      Logs data internally for remote locations
    

      SQM-LE
      Ethernet
      20°
      Ideal for remote observatories via network
    

      SQM
      None (standalone)
      80°
      Wide field, battery-operated, manual readout
    

      SQM-L
      None (standalone)
      20°
      Narrow field, battery-powered, manual use
    

The SQM-LU stands out as one of the slightly more affordable real-time logging solution with PC integration. If you want internal storage for autonomous monitoring, the LU-DL is your next step. But for most astrophotographers working with software-driven setups like NINA, the SQM-LU hits the sweet spot.

*Sky Quality Meter LU as part of a standard astrophotography setup.*

What we would like to see improved in Unihedron Sky Quality Meter – LU

This Sky Quality Meter is pricey. At the time of this review, it retails for £279 in United Kingdom. Unihedron’s standard manual version only costs £149.
This device has no mounting capability. However a 3D-printed plastic adaptor is available.
No pouch or protective case is included.

*The Standard SQM is the most affordable in Unihedron’s lineup.*

Final Thoughts

The Sky Quality Meter-LU by the Canadian company, Unihedron is more than a niche accessory, it's an essential diagnostic tool for modern astrophotographers. With the ability to record real-time sky brightness, interface with ASCOM and NINA, and contribute to light pollution research, it bridges the gap between scientific instrumentation and hobbyist practicality.

For anyone serious about improving their imaging workflow or understanding their skies on a deeper level, the SQM-LU by Unihedron deserves a place in your toolkit.