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--- wiki:astronomy:observational_astronomy:observational_astronomy [2023/11/13 08:54] – Roy Prouty
+++ wiki:astronomy:observational_astronomy:observational_astronomy [2024/11/04 19:10] (current) – Roy Prouty
@@ Line 1: / Line 1: @@
 Ground-Based Observational Astronomy is the sub-field of astronomy focused on how to make measurements of the universe from the surface of the Earth.\\ \\
-Understanding how telescopes focus light onto a detector and making sense of these measurements is is second only to making sure the measurements and their analysis are repeatable.\\ \\
+Understanding how telescopes focus light onto a detector and making sense of this detected light is is second only to making sure the measurements and their analysis are repeatable.\\ \\
 ====== Measurements ======
-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]]).
+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.\\ \\
+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.\\ \\
+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 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]].\\ \\
+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://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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