A few measurements

The variance measured with the shutter closed (a), with the shutter opened and nominal 1.7 m diaphragm (b), and with the corrector ring (c). One microampere of PMT anodic current corresponds to 30 (ADC counts)**2 (once the electronic noise variance (a) is subtracted). The average anode current without corrector ring is 0.28 microampere. The corrector ring increases the average anode current (i.e. the light collection) by a factor 2, as expected.

A star passing in the field of view of a pixel. The variance in the pixel increases for approx. 6 minutes, up to a level of one microampere above the sky background. The measurement was performed in May 2001.

A star seen by the current monitor.

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