Документ взят из кэша поисковой машины. Адрес оригинального документа : http://hea-www.harvard.edu/AstroStat/astro193/AS_notes_feb2.pdf Дата изменения: Tue Feb 3 05:41:01 2015 Дата индексирования: Sun Apr 10 11:01:20 2016 Кодировка: Поисковые слова: закон вина

Astro 193

AS cture 2 Notes Feb.2, 2015 Le

Measurements in Astronomy
1/ Telescope and Detectors: In the past the optical detectors were photographic plates. See collection of Harvard Plates being digitized: http://dasch.rc.fas.harvard.edu/ The most popular detectors in IR/optical/Xrays are : CCDcharge coupling devices. Examples: HST/ASC tp://www.stsci.edu/hst/acs ht Chandra/ACIS tp://cxc.harvard.edu/cal/Acis/ ht MPCmicrochannel plates. Examples: HST STIS/MAMA spectrograph http://www.stsci.edu/hst/stis/documents/handbooks/currentIHB/c07_performance5.htm l Chandra HRC tp://cxc.harvard.edu/cal/Hrc/ ht High energy detectors operate in oton counting mode s the photon energy is high enough to ph , a generate detectable signal in the device. Count data follow the isson distributions Po . Optical/IR detectors individual photons produce too weak signal, longer timeframes needed for accumulation of thousands of photonsnd usually provide a flux density measurement. The data a is usually treated as ussian (Normal) e. Ga typ 2/ Calibration Calibration is a measurement of the instrument characteristics. It also has a measurement error, which often is called "systematic errors". Calibration measurements improve when more data has been collected and the data can be reprocessed to account for the new calibration information. This can improve (lower the uncertainty) the quality of our scientific results. Knowledge of the instrument characteristics and calibration is important for any data analysis you want to do. Example of updated calibration of ACS and release of the reprocessed data: http://www.stsci.edu/hst/acs We also note that calibration errors are often ignored in the analysis, but in some cases they could exceed the statistical uncertainties, so our results are not as good as we would think. Important instrument information including calibration can usually be found on the instrument web pages, so look for details of your favorite instrument, learn and understand the properties of the instrument and detector. For further information you can check the first few chapters of the following book. It is specific to Xrays " ndbook of Xray Astronomy rnaud, Smith, & Siemiginowska Ha " A http://id.lib.harvard.edu/aleph/013078357/catalog