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Infrared Telescopes

  1. Dec 7, 2015 #1
    I'm trying to remember back to my undergrad physics days. Can anyone point me to a good text book to compute the following?

    Given an infrared telescope with given specifications, such as the Infrared Astronomical Satellite and a star of defined intensity in the field of view at a specific point in time, how can I compute what the in-band irradiance on the focal plane would be?

    Thanks for any references.
     
  2. jcsd
  3. Dec 8, 2015 #2

    Andy Resnick

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    First let me sketch out a basic analysis, then provide some caveats:

    If you are given the source intensity, you can calculate the power (Watts) that enters the telescope. The star is imaged to a spot of defined size (given by the optical properties of the telescope), and so you can then determine W/area of the focused image.

    Now the caveats: I noticed the words 'intensity' and 'irradiance' which implies a radiometric analysis, which uses a different definition of 'intensity' than you learned in intro physics. Intensity is Watt/steradian, and you characterize the telescope in terms of angular variables- what is the angular subtense of the star? This is different than calculating the incident irradiance from the star (which is Watt/area). Either way, if you can calculate the amount of power entering the telescope and the size of the image, you are basically done.

    Does this help?
     
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