Spectrometer and Camera setup

  • Here is a diagram to illustrate how the spectrometer is setup
  • spectra setup:
  • Light is passed through one end of the optic fibres, which is arranged as a bundle. The light passes through the cable to the other end, which is arranged in a line. The light is passed into the spectrometer in a line, where it passes through the first lens. The first lens focuses the beam onto the mirror, where the beam is reflected onto the grating. When the beam hits the grating the light is split up into its respective wavelengths. All of these separate light beams with different wavelengths then pass through the exit lens, which focuses the light once again onto the CCD chip in the camera.
  • The camera attached to the spectrometer is a SBIG ST-7E. The number of pixels in the CCD chip is 765 x 510. The camera counts the number of ADU in each pixel. To find the number of photoelectrons in each pixel, we have to multiply the number of ADU by the gain of the camera, which for the ST-7E, is 2.3. Below is an illustration of the CCD structure. As you can see, The X value ranges from 1 to 765, and the Y value ranges from 1 to 510.
  • camera ccd:
  • From the image, you can see that above the main CCD chip, there is one isolated row; this is the readout register. When the CCD is read out, each row in turn is shifted into this isolated row, at the Y=0 position. This row is then shifted to the left, where it passes through an amplifier at X=0. As this happens, an empty row in inserted at the bottom of the CCD.
  • Furthermore, there is an electromechanical shutter that is built into the camera. This shields the CCD during this process, in order to avoid any streaking of the image.
-- AshleaKemp - 16 Oct 2015

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Topic revision: r1 - 16 Oct 2015 - AshleaKemp

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