Ian Pearse
Mars
Apollo (and space) enthusiast
Posts: 308
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Post by Ian Pearse on Nov 13, 2009 17:25:34 GMT -4
A question about the Gnomon used on the Apollo missions. You can see it in various shots, giving a sense of scale and the colour reference for photo development. Was it articulated so that it would also always show the local vertical?
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Post by laurel on Nov 13, 2009 17:41:20 GMT -4
The definition NASA gives for the gnomon is, "A rod mounted on a tripod in such a way that it is free to swing in any direction and indicates the local vertical; it gives Sun position and serves as size scale. Color and reflectance scales are provided on the rod and a colorimetric reference is mounted on one leg." history.nasa.gov/EP-95/glossary.htmHarrison Schmitt said in the ALSJ, "The gnomon gave you the local vertical, a 40 centimeter scale, a shadow which gave you azimuth, and also had a gray scale and three international color references for photometric calibration. In principle, the shadow, if visible in both pictures of a stereopair, could be used to control azimuth for topographic analysis. The vertical scale of known length provided other control parameters. I am not sure anybody ever did such an analysis, given the way resources dried up after the Apollo program. I don't think anybody's ever used those photographs or the data contained in them for analysis. But we gathered it." history.nasa.gov/alsj/a17/a17.sta2.htmlHe was also known to say, "Gnomon's an island," at times, but that's another story.
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Ian Pearse
Mars
Apollo (and space) enthusiast
Posts: 308
|
Post by Ian Pearse on Nov 13, 2009 18:08:17 GMT -4
I had a feeling that was probably the case, but didn't want to state it without checking first; thanks Laurel.
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