Infrared Astronomy

Abstract

The Earth’s atmosphere transmits infrared radiation through a number of windows. Table 1 lists the seven photometric systems in use at the University of Arizona which are chosen to fit the windows between 1·0 and 25 microns. An absolute calibration (Johnson, 1965; Low, 1966) has been worked out for each wavelength band and, for reference, we include an estimate of our current limiting magnitudes using a 60-inch telescope. At about 1000 microns, observations from the ground are again possible and both our group and workers in Russia (Fedoseev 1963) and England (Baldock et al., 1965) have succeeded in making observations of celestial sources. Between 25 and 1000 microns a few data have now been obtained from stratospheric altitudes by observers using jet aircraft (Low and Gillespie, 1968) and helium-filled balloons (Hoffman et al., 1967). We can anticipate that activity of this sort will increase greatly in the near future. At present, however, most of what we know concerning the nature of celestial objects at infrared wavelengths was obtained with ground-based instruments.