lecture05 - Astronomy Picture of the Day The galaxy NGC 474...

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Unformatted text preview: Astronomy Picture of the Day The galaxy NGC 474 For future homework assignments, please write your discussion section time at the top of the page: Homework Isaac Newton 1:00 Section Refecting telescope designs Schmidt Telescopes Ordinary refecting telescopes have a small Feld o view, typically around 1 degree on the sky The Schmidt telescope allows or a much wider Feld o view, up to about 7 degrees These are used or large survey projects Astronomical Detectors A detector is what detects and/or records the light collected by a telescope The human eye as a detector: pros and cons Pros : can be fun to look at the sky through a telescope Cons : almost useless scientiFcally! You cant take long exposures to see very faint objects You cant record the data At research observatories, astronomers dont look through the telescopes! Photographic plates For about 100 years, photographic plates were the most important detectors used in astronomy A plate is a sheet of glass with a photographic emulsion Pros : Plates can be quite big- useful for survey projects They can be stored for decades or even centuries Until the 1980s, these were the main kind of detector that was available for astronomy at visible wavelengths Photographic plates Cons : They are very inefFcient ! Only about 1% of photons hitting a photographic plate will be recorded in the image They are very nonlinear detectors: the brightness in the recorded image is not directly proportional to the amount of light hitting the plate They are delicate- dont drop them! They have to be developed chemically Data cant be analyzed digitally until the developed plates are scanned into a computer CCDs in astronomy CCD = charge-coupled device CCDs in astronomy Cons : CCDs are individually small (but many CCDs can be used...
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This note was uploaded on 04/20/2008 for the course PHYS 20A taught by Professor Staff during the Fall '02 term at UC Irvine.

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lecture05 - Astronomy Picture of the Day The galaxy NGC 474...

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