[SQM] Can SQM-LE withstand full sunlight?

Anthony Tekatch anthony at unihedron.com
Fri Oct 10 20:48:30 UTC 2008

Hello Henk,

Regarding Sunlight on the SQM-LE:
The unit can handle direct light from the Sun, however, extreme heat may
melt the plastic covering the sensor. We have had the unit get direct
hits from the sun at our 43deg location, but the unit was indoors under a
temperature controlled environment. The temperature sensor went up to 50
C at times and no ill effects were reported. Because there is somewhat of
a "magnifying glass" in the lens, it is recommended that you try to point
the meter away from direct sunlight if possible. But the lens does not
focus to a point so there is little worry about generating enough heat to
damage the unit.

It is unlikely that any long term calibration loss will occur by being
heated by the sunlight because the raw sensor provides a digital output.

However, keeping the SQM-LE under a plastic dome may eventually receive
darker readings if the plastic degrades over time from UV exposure. It is
recommended that calibration readings are taken periodically to determine
the effects of dome cover discolouration. Or better yet, use a glass cover.

The meter is not designed to measure sunlight, so anything brighter
(lower reading) than about 6 magnitudes per square arcsecond will result
in a reading of 0. Using a low value neutral density filter over the unit
will help reduce the sensitivity, but fixing that in place will likely
result in no reading at night. Generally, any light entering the SQM-LE
which is brighter than "bright twilight" saturates the meter.

Best regards,
Anthony Tekatch

On Fri, 10 Oct 2008 15:33:52 +0200, "Henk Spoelstra" <spoelstrah.yahoo at telfort.nl> wrote:

> Dear Anthony,
> Can the SQM-LE be left under an acrylic dome during daytime with full
> sunlight? Would any damage occur or drift of calibration?
> Are the readings under sunlight conditions (which I also try to
> monitor) then still meaning full?
> Kindest regards,
> Henk Spoelstra

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