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

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Astronomy Picture of the Day The galaxy NGC 474
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For future homework assignments, please write your discussion section time at the top of the page: Homework Isaac Newton 1:00 Section
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Reflecting telescope designs
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Schmidt Telescopes Ordinary reflecting telescopes have a small field of view, typically around 1 degree on the sky The Schmidt telescope allows for a much wider field of view, up to about 7 degrees These are used for large survey projects
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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 scientifically! You can’t take long exposures to see very faint objects You can’t record the data At research observatories, astronomers don’t look through the telescopes!
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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
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Photographic plates Cons : They are very inefficient ! 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- don’t drop them! They have to be developed chemically Data can’t be analyzed digitally until the developed plates are scanned into a computer
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CCDs in astronomy CCD = “charge-coupled device”
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CCDs in astronomy Cons :
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