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UBC Theses and Dissertations

Image isocon television system for the detection of astronomical spectra Buchholz, Vernon Lawrence


A complete system for the detection and recording of astronomical spectra has been constructed using an image isocon (E.E.V. P850) television tube as detector. The detector will accomodate two spectra 80 millimeters in length and has the spectral response of an S-20 photocathode. Recording is onto IBM-compatible magnetic tape via an on-line computer. The user is also provided with a real time display of the spectra on an oscilloscope via the computer. A description of the video signal circuits is given. Schematic diagrams of the control unit constructed by the author and the modified camera are shown. A method of determining the modulation transfer function of the detector, based on the Fourier analysis of the signal output for a known signal input, is described. The MTF as a function of light level, exposure time, and target temperature is investigated. It can be seen that the best MTF for a particular exposure time occurs at the lowest target temperature. The MTF far exceeds that predicted as the maximum by direct application of the analysis of Krittman (1962). It is assumed that the Krittman analysis can not be applied to the P850 image isocon with its large target mesh-to-target spacing and thin target.

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