Radial Velocities In The Zodiacal Dust Cloud

The Zodiacal Light, conveniently abbreviated to ‘ZL’, is the name given to a diffuse cone of light seen in the Western sky in the evening, from around the end of twilight, and in the Eastern morning sky just before dawn. In the latter incarnation it has been called the ‘False Dawn’. If it could be […]

The Zodiacal Light – the phenomenon Part 2

Physical parameters and models of the ZL The variables of interest in the interplanetary medium are the number density, size, shape and albedo of the particles, their distance from the Sun, and their speed and direction of motion, almost all of which may be a function of any of the others. In addition, we would […]

The Zodiacal Light – the phenomenon Part 3

Review of the period of my observations of the ZL, 1970-1974 It was the intention of this PhD study to fill in the gaps and uncertainties left in observational data in 1970; to make a comprehensive survey of a Doppler-modified Fraunhofer line in the ecliptic plane at all elongations from the Sun, and hence constrain […]

The Zodiacal Light – the phenomenon Part 4

ISO (Infrared Space Observatory) data In spite of its faintness in optical wavelengths, the Zodiacal Light is the dominant source of the medium-infrared sky brightness as seen from the Earth. The cross-over point is at a wavelength around 3.5 microns; at wavelengths shorter than this, the major part of the energy is scattered sunlight (with […]

Preparations and experimental details 1971-1974 (Zodiacal Dust Cloud) Part 1

This topic details the preparations for making the radial velocity measurements, and the manner in which observations were actually performed. It includes the choice of wavelength and resolving power, the site, the building of the observatory, and the construction of the Fabry-Perot Interference Spectrometer – its optics, control electronics, counting electronics, calibration equipment, and information […]

Preparations and experimental details 1971-1974 (Zodiacal Dust Cloud) Part 2

New features of the instrument In this section I detail my own improvements, in which most of the equipment was redesigned and rebuilt. Fore-optics The front end of the F-P optics was changed so that the coelostat’s ‘final’ lens now delivered an f/17 beam directly from the coelostat mirrors, removing the necessity for a relay […]

Preparations and experimental details 1971-1974 (Zodiacal Dust Cloud) Part 3

Intensity calibration box To calibrate the instrument in intensity, an attachment was made, shown in the photograph, Figure 2.16, to the front end of the spectrometer. Its construction is shown in Figure 2.17. The source was an M/F pilot bulb, calibrated at the National Physical Laboratory for luminous intensity and colour temperature at a standard […]

Reduction of the data (Zodiacal Dust Cloud) Part 1

This topic contains an account of the processes applied to the raw scans, after the observations were completed, to transform them into a set of corrected spectra, suitable for the extraction of parameters to compare with theory, together with some preliminary observations on the data. I describe here the absolute calibration of intensity, and the […]

Reduction of the data (Zodiacal Dust Cloud) Part 2

Treatment of a single scan A typical ‘raw data’ scan is shown in Figure 3.7a,which is plotted directly from the printout values of the signal channel. In the diagram the scale of lamp number has already been converted to a wavelength scale, as was done for each scan using the results of section 3.2. The […]

Reduction of the data (Zodiacal Dust Cloud) Part 3

Variation of daily average emission The well-established enhancement of CaII emission at times of high meteor activity (Vallance and Jones 1956) suggested to us that there might be a correlation between MgI emission and meteor showers. The Orionid shower has a maximum activity around October 20th and the Lyrid shower about April 21st. The September […]