Concept Testing System

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We first built a concept testing system to demonstrate that brightness measurements of stars at a few wavelengths can be used to derive a model for the transmission of the atmosphere that is as precise as what can be derived with spectroscopic measurements.

The setup for concept testing system is as follow. There are two 8-inch telescopes: one with a fiber at the focal plane that feeds an Ocean Optics JAZ spectrograph, another with an SBIG ST-402ME CCD at the focal plane. The imaging telescope has a cap on the front that holds five filters, each coupled to a "wedge prism" that diverts a ~40mm part of the pupil ~2 arcminutes. This creates five individual images on the CCD of the same star. The two telescopes are co-mounted on a tripod and are aligned to look at the same star, so we simultaneously obtain a spectrum and five narrow-band images of a star.

Image 3

We have made multiple photometric and spectroscopic measurements simultaneously with the concept testing system described above at both Texas A&M observatory and McDonald observatory. Figure below shows one of the measured atmospheric throughout (blue dots) from the observed spectra, after removal of the instrumental throughput and the stellar spectrum and best fit model (black lines) from the synthetic color indices of that measured atmospheric throughput. We conclude that the atmospheric model derived from color measurements can be an accurate representation of the true atmospheric transmission with an adequate database and a good imaging quality system.

Image 4

Read more about the Concept Testing System
  • SPIE 2012 Conference Preceeding
  • SPIE 2012 Poster


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    Astronomy Group
    4242 TAMU
    College Station, TX 77843-4242
    Ph: (979) 845 7717
    Texas A&M University - College of Science