Unihedron SQM-LU-DL, Руководство оператора

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12 Calibration
The SQM-LU-DL is factory calibrated and a sheet of the calibration values was provided with the unit. Contact Unihedron
with your unit’s USB S/N if you need a copy of the original calibration sheet.
Some possible reasons for recalibration are:
1. A new covering/housing is being used besides the small case that the unit was shipped with.
2. A regular maintenance program is desired. There is no great need for this as the SQM-LU-DL has no analog
components.
3. Compensation for aged housing, if a plastic dome is used that might have degraded over time.
4. Replaced lens or changed field of view for experimental reasons.
12.1 Recalibration
There is no easy way to perform in-field recalibration. It is recommended to send the unit back to Unihedron for proper
calibration. There is a nominal fee for recalibration and shipping. Please contact Unihedron for details.
12.2 Light calibration
The sensor must have a reference point for an amount of light against the signal produced. It is not recommended that
this be done after factory calibration and relied upon since an improper setup will result in non-standard results.
A fluorescent light or green LED is used to simulate the spectrum that the meter would see during the night sky. A
light meter is used to adjust the light reading to 13.5 fc at the place of the SQM-LU-DL. The light calibration routine
inside the SQM-LU-DL expects to see this value.
The light that the SQM-LU-DL and light meter see must be coming from an evenly lit surface.
The “light calibration” command can be sent to the unlocked SQM-LU-DL to set the calibration value.
12.3 Dark calibration
The optical sensor in the SQM-LU-DL produces a reading even when totally dark. This “dark level” reading must be
determined so that the meter can compensate for it.
The method of dark calibration is simply to prevent any light from entering the meter then execute a “dark calibration”
command to the unit. A darkroom bag is one way to prevent light from entering the unit.
The optical sensor provides timed pulses depending on the amount of light entering. In a dark environment the pulses
will be long. The meter has a timeout of 300 seconds, so the dark calibration will take at least 5 minutes (300 seconds)
to perform.
Place the unit in a dark environment and monitor the timed readings (rx reading request) until they are consistent,
normally the value is in the 80-300 second range, then execute the “dark calibration” command.
12.4 Confirmation
Once the calibration has been done, you should be able to get a light reading from the unit at the calibration light level
of the same value as the value printed on your calibration sheet in the “Calibration offset” field, Normally this field has
a value of 8.71 mags/arcsec
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