Unihedron Sky Quality Meter

Yes, yes, we know. When you think Unihedron, you think Unihedron Sky Quality Meter. We do, too.

The names Unihedron and the Unihedron Sky Quality Meter have become synonymous with measurement of sky brightness. Indeed, it’s hard to imagine a Sky Quality Meter tool that has had greater impact on quantification of local light pollution than the Unihedron Sky Quality Meter.

Unihedron’s original SQM set the standard and has since evolved into a comprehensive range of specialized tools, including the SQM-L with lens for focusing on a narrow field-of-view, the SQM-LU with USB connectivity, the SQM-LE with Ethernet connectivity, the SQM-LR with RS232 connectivity and, most recently, the SQM-LU-DL, a narrow field-of-view, USB-connected version with data-logging capability. But that’s not all they have to offer.

Unihedron Sky Quality Meter
Image 1: Unihedron’s CapSelector.


Unihedron’s CapSelector ($24.95US) provides an inexpensive way to tune a VLF loop over a wide range of capacitances – 120 to 5510 pF (picofarads or a million millionth of a farad). It replaces expensive and bulky high-value variable capacitors or decade capacitor banks. It is a passive device and therefore requires no power.

If you’re interested in building your own radio telescope, consider How to Build Your Own Radio Telescope,by Percival Andrews.

Unihedron Sky Quality Meter
Image 2: The Unihedron Nu-B Spectral Light Source.

Nu-B Spectral Light Source

Unihedron’s Nu-B ($59.95US) is a source of broad spectrum (white), blue, green, yellow, orange/IR and red light for optics demonstrations and experiments designed by Dr. Doug Welch and Anthony Takatch. It produces new-monochromatic light without the safety concerns of laser diodes.

The Nu-B features single-button operation for selection of individual sources or all six at once, two brightness levels, filtered LED light results in narrow emission bandwidths and microprocessor control. It is battery operated, so no AC adapters, wires or plugs are required, and it is powered by two included CR2032 coin cells. An auto-off function cuts power after two hours of use to prolong battery life, but it is designed to operate for 100-plus hours on the two batteries. A holographic diffraction grating slide is included.

Image 3: Slide-mounted diffraction grating.

Diffraction Grating

The diffraction grating included with the Nu-B Spectral Light Source is also available separately for $4.95US. The overall slide measures 2 by 2 inches (50.8 by 50.8 mm), while the dimensions of the contained grating are 1.325 by 0.875 inches (79.4 by 22.2 mm). The grating features 750 lines per millimeter (19,050 lines per inch) and has no coating to reduce secondary reflections.

Open-Source Software

Unihedron offers a complete, free, open-source Unit Conversion Utility called Gonvert that runs on Linux and Windows. All units in a category get converted while you type. There’s also 4-to-20mA, which utility calculates various numbers related to 4-to-20mA conversions used in PLCs. By typing values into any cell, the resultant units are automatically calculated.

And Posters Galore!

The above products are very cool, and we consider Unihedron’s SQMs essential, but our favorites are Unihedron’s posters. Take for example, its Primes poster ($49.95US), which displays 122 prime numbers. But step closer – closer, still – and 350,389 primes become visible … at least to those of us with sufficient visual acuity.

Similarly, Unihedron’s Pi poster (also $49.95US) displays the most commonly-recognized digits … from a distance. When close enough, 350,390 digits of Pi are visible. Other posters include Phi and Root 2.

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