Geodesic
Photographic Determination of Heliographic Coordinates of Sunspots Without Taking Double Photos
Publications of the Department of Astronomy, Tome 6 (1976) no. 1.

Voir la notice de l'article provenant de la source eLibrary of Mathematical Institute of the Serbian Academy of Sciences and Arts

The idea of the method is to achieve high precision in determination heliographic coordinates of sunspots, without taking double exposure photographs. For this purpose, with a level, the parallelity of one side of the photographic plate to the horizont is ensured. The moment of exposure is noted in UT. 
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     author = {Aleksandar Tomi\'c},
     title = {Photographic {Determination} of {Heliographic} {Coordinates} of {Sunspots} {Without}  {Taking} {Double} {Photos}},
     journal = {Publications of the Department of Astronomy},
     pages = {65 - 67},
     publisher = {mathdoc},
     volume = {6},
     number = {1},
     year = {1976},
     url = {http://geodesic.mathdoc.fr/item/PDA_1976_6_1_a11/}
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Aleksandar Tomić. Photographic Determination of Heliographic Coordinates of Sunspots Without  Taking Double Photos. Publications of the Department of Astronomy, Tome 6 (1976) no. 1. http://geodesic.mathdoc.fr/item/PDA_1976_6_1_a11/