A. Keith Pierce

Performance of an Eight-Inch Babcock Grating in a Large Vacuum Spectrograph

To obtain true profiles of Fraunhofer lines, corrections for instrumental profile, ghosts, scattered light, etc., must be applied to the observations. A study of a 600 groove/mm Babcock grating in a high dispersion, vacuum spectrograph (8 mm/A, 5th order, λ 5461) is presented. Photographs of the hyperfine structure of the mercury line λ 5769 show a resolution of 630 000 in the 5th order. Photographs of Hg λ 2536 with a microwave-excited 198 lamp as a source exhibit a weakly self-reversed line. The measured separation of the components is 0.0021 A, corresponding to a resolving power of 1 200 000 in the 11th order. The instrumental profile, the intensities of satellite lines, and the ghost system have been determined by photoelectric scanning of the line λ 5461 of isotopic mercury. A determination of the vertical apparatus function shows that its half width is 15% wider than the theoretical value. The total intensity of the ghosts is 1.8% in the 5th order. A brief study of polarization effects and the nature of the blaze is presented. The general spectrographic scattered light was found to be 0.7%.

The center-to-limb wavelength shift of a number of Fraunhofer lines

The center-to-limb wavelength shifts of the cores of faint, medium and strong Fraunhofer lines are presented: Fei 3767, Caii 3968, Ceii 4222, Cai 4227, Nai 5896, Baii 6497, and Ki 7699.

The Photosphere of the Sun

An empirical model of the photosphere rests on observations of: (1) the solar constant—which fixes the temperature scale, (2) limb darkening—from which the variation of temperature with depth throughout the atmosphere is determined, and (3) the energy distribution—which, together with limb darkening, reveals the opacity at each depth and for each wavelength.

Wavelength Shifts in the Solar Photospheric Spectrum

Wavelength shifts converted to velocities between solar lines observed at disc center and laboratory wavelengths of Fe i, Fe ii, Ti i, Ni i, and Fe i lines in the near infrared are plotted as a function of the logarithm of their solar equivalent width in milliångstroms. The need for wavelengths based on the wavelength standards is stressed. A comparison of photographic Fe i solar wavelength is shown to agree, on the average, with Fourier Transform Spectrometer solar wavelengths within less than 0.5 milliångstroms. Using Balthasars limb effect tables we convert the disc center velocities to limb velocities and find, though the scatter is large, that there is little evidence for a super-gravitational red shift.

The observed limb effect in Fraunhofer lines, I

The absolute limb effect is presented for Fei lines λ 3767 and λ3969; for five Tii lines of multiplet 42 near λ 4535 and one Tiii line at λ 4534; two lines of Mgi, λ 4571 and λ 5172; two lines of Baii at λ 5854 and λ 6497. The scattered light of the McMath solar telescope is illustrated by several figures but not applied to the limb-effect observations. It is suggested that the supergravity shift at the limb is the result of scattering of the atoms in anisotropic velocity field.

The morphology of solar granulations and dark networks

Solar granules are classified into four groups according to their shapes and splitting by sharp rifts crossing them. The appearance and evolution of ‘white-light dark networks’ is described.