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| wiki:astronomy:observational_astronomy:observational_astronomy [2023/11/14 12:30] – Roy Prouty | wiki:astronomy:observational_astronomy:observational_astronomy [2024/11/04 19:10] (current) – Roy Prouty |
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| Measurements made with the tools of observational astronomy (telescopes and detectors attached to them) are measured from science images and are given in either [[wiki:astronomy:radiative_quantities|absolute]] or [[wiki:astronomy:magnitude|relative]] scales.\\ \\ | Measurements made with the tools of observational astronomy (telescopes and detectors attached to them) are measured from science images and are given in either [[wiki:astronomy:radiative_quantities|absolute]] or [[wiki:astronomy:magnitude|relative]] scales.\\ \\ |
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| The digital detector attached at the focal plane of the telescope generates [[~:..:measurements:what_the_detector_measures|counts]]. These counts contain the desired source signal which has been attenuated along its optical path due to atmospheric extinction along with a number unwanted signals/effects. These are the additional photon flux due to the background sky brightness as well as the unwanted detector effects: the dark signals and the erroneous pixel-to-pixel variation in sensitivity due to inhomogeneities in the detector or an imperfect optical system.\\ \\ | The digital detector attached at the focal plane of the telescope generates [[~:..:measurements:what_the_detector_measures|counts]]. These counts contain the desired source signal which has been attenuated along its optical path due to [[~:extinction|atmospheric extinction]] along with a number unwanted signals/effects. These are the additional photon flux due to the background sky brightness as well as the unwanted detector effects: the dark signals and the erroneous pixel-to-pixel variation in sensitivity due to inhomogeneities in the detector or an imperfect optical system.\\ \\ |
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| The removal of the unwanted signal and calibration to account for detector, optical system, or atmospheric effects in the frame counts is called Data Reduction. The result of a properly reduced frame is a science frame. It is from a science frame that most physical quantities can be estimated. | The removal of the unwanted signal and calibration to account for detector, optical system, or atmospheric effects in the frame counts is called Data Reduction. The result of a properly reduced frame is a science frame. It is from a science frame that most physical quantities can be estimated.\\ \\ |
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| The removal of the detector effects is covered in [[~:..:data_reduction_telescope|Data Reduction I: Removing Local Effects]] | The removal of the detector and optical system effects is covered in [[~:..:data_reduction_telescope|Data Reduction I: Reduction to Top-of-Telescope]]. The identification and further reduction of the counts associated with sky brightness (a.k.a., light pollution) is covered in [[~:..:data_reduction_skybrightness|Data Reduction II: Removal of Sky Brightness]]. The conversion of the counts to a magnitude scale and the final step of data reduction is handled in [[~:..:data_reduction_toa|Data Reduction III: Reduction to Top-of-Atmosphere]]. The quantization of confidence in all of these measurements is discussed in [[~:..:snr|Signal-to-Noise]].\\ \\ |
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| Before interacting with or even [[~:..:science_image|generating a science image]], any astronomer should be familiar with exactly [[~:..:measurements:what_the_detector_measures|what the detector measures (photons)]]. From this understanding of radiant energy in the form of integrated spectral radiance or of photons, astronomers can extract absolute physical quantities (e.g., [[~:..:measurements:radiative_flux|radiative flux]]) or relative quantities (e.g., [[~:..:measurements:magnitudes|magnitudes]]). | Before interacting with or even [[~:..:science_image|generating a science image]], any astronomer should be familiar with exactly [[~:..:measurements:what_the_detector_measures|what the detector measures (photons)]]. From this understanding of radiant energy in the form of integrated spectral radiance or of photons, astronomers can extract absolute physical quantities (e.g., [[wiki:astronomy:radiative_quantities#radiant_flux|radiative flux]]) or relative quantities (e.g., [[wiki:astronomy:magnitude|magnitudes]]). |
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| - https://mirametrics.com/help/mira_al_8/source/magnitude_calculations.htm | - https://mirametrics.com/help/mira_al_8/source/magnitude_calculations.htm |
| - https://www.aavso.org/sites/default/files/publications_files/ccd_photometry_guide/CCDPhotometryGuide.pdf | - https://www.aavso.org/sites/default/files/publications_files/ccd_photometry_guide/CCDPhotometryGuide.pdf |
| | - http://www.phys.ttu.edu/~ozprof/honours3.htm#:~:text=In%20differential%20photometry%2C%20the%20object,derive%20the%20difference%20in%20brightness. |
| | - https://wellbeing.ihsp.mcgill.ca/publications/cpblThesis/node20.html |
| | - https://hamamatsu.magnet.fsu.edu/articles/ccdsnr.html |
| | - https://www.public.asu.edu/~rjansen/ast598/ast598_jansen2014.pdf |
| | - https://www.astro.auth.gr/~seeing-gr/seeing_gr_files/theory/node3.html#:~:text=is%20the%20zenith%20distance%20(the,at%20the%20time%20of%20observation).&text=slope%20equal%20to-,.,for%20blue%20light%20than%20red. |
| | - https://noirlab.edu/science/programs/ctio/instruments/goodman-high-throughput-spectrograph/data-reduction-pipeline |
| | - https://www.astropy.org/ccd-reduction-and-photometry-guide/v/dev/notebooks/08-03-Cosmic-ray-removal.html |
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