Seeing in the Ultra-Violet

Abstract

According to different authors^{1, 2}, under appropriate conditions seeing is possible in the ultra-violet down to a wave-length as small as 3100 A. This fact has been confirmed on 21 persons (age 25–50 years) using as light sources discharge tubes containing (1) high-pressure mercury, (2) low-pressure cadmium and zinc (both in neon). The tubes were of quartz, 15 mm. × 120 mm. Visible light and short waves (<2700) were cut out by a red purple corex filter. Using one or more filters (each 5 mm.) the intensity of the Hg line 4047 relative to 3650 and 3130 could be varied within wide limits. A small monochromator (without second slit) was used to separate the different wave-lengths. As a result, the visibility for =3650 relative to 4047 could be determined. It was also possible to estimate the visibility for 3130.