Abstract
We have developed a photograph filtering technique to search for QSOs with objective prism plates. After off-focus reproduction, the signal-to-noise ratio increases and some spectral lines in the prism spectra may be recognized by eye against the noise. Principle of this technique is discussed.
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He, R., Men, L. The off-focus photograph technique for low dispersion spectra. Astrophys Space Sci 165, 299–311 (1990). https://doi.org/10.1007/BF00653297
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DOI: https://doi.org/10.1007/BF00653297