VISUAL PERFORMANCE IN ASTRONOMY NEAR THE SCOTOPIC THRESHOLD PART 2: VISION VERSUS CCD

摘要

Based on the integration times reported in Part 1 (see the preceding paper, Bishop & Lane 2004a), the performance of vision and of a CCD in registering images of a faint star, a spiral galaxy, and an emission nebula are compared. Also, the images of the galaxy are compared to a pre-photographic mid-19th-century sketch made using the largest telescope of that era. The results indicate that, contrary to common wisdom, within the limit of its integration time the performance of vision near the scotopic threshold exceeds that of a CCD. That the eye can perform so well despite its low quantum efficiency, warm operating temperature and limited spectral response is attributed to two properties of the scotopic visual system: (ⅰ) the displacement of the rod photoreceptor spectral response toward higher quantum energies; (ⅱ) the binning of rod photoreceptors into a variety of parallel summation pools.