SHARPII+ Calibration Page

Calibration Data

A set of flat field images for all broad-band filters and all lens scales are taken during each SHARP observation run. The data are used to obtain gain and bad pixel images. All of the gain and bad pixel images from previous SHARP observations runs are available for download.

Zero Point Monitoring

Zero point values are monitored for a number of wavebands during each SHARP observation run (weather permitting). All measurements from December 1998 onwards have been tabulated.

Astrometric Calibration

Whenever possible data are taken of an astrometric field (near Theta Orion in the Trapezium cluster). A detailed report on the results is available at: http://www.bdl.fr/priam/adonis/calib.html

Results from measurements of the Theta 1 C field on 10 December 2001 have been kindly made available by Adonis observer Rainer Koehler.

Bad Pixels

A set of bad pixel images are obtained during each observing run by using the pipeline routine adogain
September 2001: Number of dead pixels = 355 (0.5 per cent)
Image (North - down, East - left)

Dark Current

The dark current for the SHARP detector is non-linear. Measurements of the dark current have been made over several observation runs. The results are available below.

December 2001
Plot of measured average signal (ADU) versus integration time (s)
Minimum flux offset = -30713.3 ADU
Fitted Function = 14.738+ (0.0536002 * t) - (14.7381 * (exp(-0.249966* t))) ADU
October 2001
Plot of measured average signal (ADU) versus integration time (s)
Minimum flux offset = -30710.9 ADU
Fitted Function = 13.2681+ (0.0847261 * t) - (13.2681 * (exp(-0.243961* t))) ADU
June 2001
Plot of measured average signal (ADU) versus integration time (s)
Minimum flux offset = -30713.2 ADU
Fitted Function = 12.5206 + (0.207276 * t) - (12.5206 * (exp(-0.418496 * t))) ADU
December 1995
(taken from xreport "Laboratory Test Results on SharpII Infrared Camera")
Plot of measured average signal (ADU) versus integration time (s)
Fitted Function = 16.60 + (0.00225 * t) - (16.60 * (exp(-0.03723 * t))) ADU

Note: Diamonds - average measured signal, vertical line - standard deviation, solid line - fitted function

Linearity

To calculate the linearity range of the SHARP detector an illuminated flat screen was observed (3.6-m dome flat screen with lamp) in H-band using the 0.035 arcsec/pixel scale and with varying integration times. The resulting average signal on the detector after dark subtraction and dead pixel correction is available below:

October 2001
Plot of measured average signal (ADU) versus integration time (s)
Measured linearity range: up to 15500 ADUs (-29100 to -15100 ADUs raw signal)
December 1995
Plot of measured average signal (ADU) versus integration time (s)
Measured linearity range: up to 21715 ADUs (-30715 to -9000 ADUs raw signal)

Note: Diamonds - average measured signal, vertical line - standard deviation, solid line - fitted function