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| wiki:astronomy:observational_astronomy:measurements:what_the_detector_measures [2023/11/13 16:34] – Roy Prouty | wiki:astronomy:observational_astronomy:measurements:what_the_detector_measures [2023/11/14 12:31] (current) – Roy Prouty |
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| ====== What does the detector measure? ====== | ====== What does the detector measure? ====== |
| tl;dr: Photons. CCDs and CMOSs are photon counters.\\ \\ | tl;dr: Photons. CCDs and CMOSs are photon counters. The number that it counts per pixel is called the counts, the LUM, or the ADU.\\ \\ |
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| ===== What's a count? ===== | ===== What's a count? ===== |
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| ===== Isolating the Radiative Energy ===== | ===== Isolating the Radiative Energy ===== |
| The [[wiki:physics:semiconductor_physics#origin_of_the_bias|voltage applied to a pixel]] and the [[wiki:physics:maxwell_boltzmann_distribution|temperature of the electrons]] clearly arise from the detector itself. These contributions to the counts must be [[~:..:..:data_reduction_telescope|calibrated]] away. After this calibration, the counts speak to only the liberated electrons by the radiative energy associated with incident photons.\\ \\ | The [[wiki:physics:semiconductor_physics#origin_of_the_bias|voltage applied to a pixel]] and the [[wiki:physics:maxwell_boltzmann_distribution|temperature of the electrons]] clearly arise from the detector itself. These contributions to the counts must be [[~:..:..:data_reduction_telescope|calibrated]] away. After this calibration, the counts speak to only the liberated electrons by the [[wiki:astronomy:radiative_quantities|radiative energy]] associated with incident photons.\\ \\ |
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| After this calibration, the counts remaining in the image should be proportional to the energy received from the source alone. Further photometric calibration can be performed to relate these counts to relative or absolute [[~:..:radiative_flux|physical units]]. | After this calibration, the counts remaining in the image should be proportional to the energy received from the source alone. Further photometric calibration can be performed to relate these counts to some [[wiki:astronomy:magnitude|magnitude scale]] or to some absolute scale via some measure of [[wiki:astronomy:radiative_quantities|radiative quantities]]. |
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| {{tag>[pls-review]}} | {{tag>[pls-review]}} |