The theoretical relation between scintillation and shadow bands.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The theoretical relation between scintillation and shadow bands. Keller, Geoffrey Abstract Direct quantitative photographic photometry of stellar shadow bands is difficult since even the brightest stars do not provide enough light for an exposure short enough to stop the motion. An alternative method is therefore suggested in which the light of a star is observed with a photocell which can record intensity fluctuations in such a way that their r.m.s. deviations from the mean can be measured, at individual frequencies and when integrated over all frequencies. During the measurements the objective of the telescope is covered by a diaphragm containing two small holes having a known separation. If the separation of the holes is small compared to the size of the average patch of light, the light coming through the two holes will fluctuate in unison. Consequently the r.m.s. fluctuation of the total light coming through both holes will be twice the fluctuation of the light through a single hole. On the other hand, if the holes are much farther apart than the diameter of a patch of light, the fluctuation of the light from the two holes will be uncorrelated. In this latter case the r.m.s. amplitude of the combined light fluctuation will be only the square root of two times the fluctuation of light from a single hole. A mathematical analysis shows that observations of this kind can give the complete auto- correlation function of shadow band intensities and the wave-length spectrtim of their undulations. From observations made at individual frequencies the combined space-time autocorrelation function can be obtained, except for an uncertainty with respect to the direction in which the pattern is moving. This work was sponsored in part by the Cambridge Air Force Research Center through a contract with the Ohio State University Research Foundation. Perkins Observatory, Delaware, Ohio. Publication: The Astronomical Journal Pub Date: October 1954 DOI: 10.1086/107034 Bibcode: 1954AJ.....59..326K full text sources ADS |