An illustration of a passage instrument,an astronomical tool used to determine the time stars pass through the local meridian. Knowing this allowed astronomers to determine the precise time and correct their observatory clocks. After 1913,the passage instrument was discarded in favor of a crystal radio-detector used for determining the drift of the observatory clocks | |
Licence : | Droits gérés |
Crédit: | Science Photo Library / NYPL / Science Source |
Taille de l’image : | 3411 px × 3212 px |
Model Release : | Non requis |
Property Release : | Non requis |
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