180 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1950 



so-called "Baily's beads" at tlie beginning and end of the total 

 eclipse. The cinematography of the flash spectrum may serve the 

 same purpose, and has even some advantage because of the exact 

 spectrophotometric methods that may be applied in this case. 



If the contacts may be defined and measured accurately enough, 

 observations of the contacts at various points along the track of the 

 eclipse may give very exact information as to the distances between 

 the points of observation on the surface of the earth. The informa- 

 tion obtained has thus a direct geodetic interest. The first attempt 

 to make a geodetic application of the determination of eclipse con- 

 tacts was made by Banachiewicz, and after him the idea was taken 

 up with very great interest by the Finnish astronomer and geodesist. 



Second contact 

 Photometric profiles 



""'Lund eAp> 



Figure 4. — Tlie lunar contour determined photometrically from the records of 

 the flsh-spectrum according to the results from the Stockholm expedition (full- 

 drawn curve) and the Lund expedition (dotted curve). Second contact. 



I. Bonsdorff. Attempts to apply the cinematographic methods of 

 contact determination have been made by Finnish and Swedish eclipse 

 expeditions using direct cinematography of the solar disk, as well as 

 cinematography of the flash spectrum. 



At the eclipse in northern Sweden in 1945 the three Swedish ob- 

 servatories of Lund, Stockliolm, and Uppsala had the cinematography 

 of the flash spectrum on their programs, with elaborate instrumental 

 equipments. The exact timing of each exposure on the film was made 

 by recording the exposures together with time signals by means of a 

 cathode-ray oscillograph. Very appropriate instruments of this kind 

 were designed by K. G. Malmquist, H. Norinder, W. Stoffregen, and 

 L. Stigmark. The cinematographic film was photometrically stand- 

 ardized by means of a sensitometer. 



The photometric measurements allow us to determine the rate of 

 decrease of the intensity of the continuous spectrum at the extreme 

 limb of the sun, i. e., the "sharpness" of the limb. It has been found 



