Unihedron SQM-LU-DL, Operator'S Manual

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9 Installation
The SQM-LU-DL uses an internal voltage-regulator to bring the incoming USB 5VDC voltage from the PC down to
3.3VDC. The 5V USB voltage is measured and logged during data-logging operation.
The battery adapter uses an in-line-mounted voltage-regulator to bring the 9VDC down to 5VDC.
9.1 Mechanical installation
Unihedron sells an enclosure that is suitable for mounting either the SQM-LE, SQM-LU, SQM-LR, SQM-LU-DL into.
You can read more about it, including plans to build your own at www.unihedron.com/projects/sqmhousing/ .
Figure 9.1: Housing
9.1.1 Cover selection
If the unit is to be mounted in exposed location, we recommend the Unihedron plastic weatherproof housing with glass
window plate, or an acrylic dome. Acrylic domes will last 2-3 years but eventually weather on the surface. It is not clear
that this will affect the reading much. The best test would be to swap a weathered and new one back and forth when
changing one out. Presumably the main consideration would be to keep the domes clean every so often and to make sure
that the mounting plane is painted black to that it doesn’t reflect light back to the inside of the dome and then back into
the meter.
Source of scrylic domes: www.globalplastics.ca/domes.htm
9.1.2 Cover calibration
Since the meter is not weather-proof, it must be protected in some way from the elements. The Unihedron meter housing
or a plastic dome is recommended. This will reduce the incoming light (approximately 15-20%).
Because a covering will reduce the incoming light, the resultant reading will be darker (higher
mag
arcsec
2
value). The offset
determined by a simple light experiment should be subtracted from the reading.
Apply this subtraction offset as a negative value, i.e. if you measured 16.60 outside the covering, then 16.75 under the
dome, then an offset of -0.15 should be applied to all readings.
An example using the UDM software; if your offset is -0.12 and your factory calibrated light calibration offset is 19.92
then you should change the light-calibration-offset on the calibration-tab to 19.80. European users will see and use a
comma instead of a decimal point.
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