Elements of astronomy ... with explanatory notes, and questions for examination (1855)
Brocklesby, John, 1811-1889 · New York, Farmer, Brace & co. · leaf 144
le ASB the sun. Now if a spot was not in con-tact with the suns surface but moved in the large circleCDP; it is obvious that it would be impossible for a per-son at E to see it crossing the suns surface except while How does it move, and where disappear ? What is the period of a spots visibility… … SOLAR SPOTS PERIODS OF VISIBILITY AND INVISIBILITY. and it would be invisible all the time it was passing fromC through the rest of the circumference of the large circle,round to D again. Now as the arc CD is much smallerthan the other part of the circumference of the largecircle ; to wit, CPD, the…
Astronomy
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