Table:
text: Smithsonian Astrophysical Observatory
History
Remote stations
Station Type_ Latitude Longitude El_m Opened Closed Coordinates_
Mount Wilson, California Solar 34º13`N 118º56`W 1737 1908 1920 34°13′S 118°56′W﻿ / ﻿34.217°S 118.933°W
Hump Mountain, North Carolina Solar 36º8`N 82º0`W 1500 1917 1918 36°8′N 82°0′W﻿ / ﻿36.133°N 82.000°W
Calama, Chile Solar 22º28`S 68º56`W 2250 1918 1920 22°28′S 68°56′W﻿ / ﻿22.467°S 68.933°W
Mount Montezuma, Chile Solar 22º40`S 68º56`W 2711 1920 ? 22°40′S 68°56′W﻿ / ﻿22.667°S 68.933°W
Mount Harquahala, Arizona Solar 33º48`N 113º20`W 1721 1920 1925 33°48′N 113°20′W﻿ / ﻿33.800°N 113.333°W
Table Mountain, California Solar 34º22`N 117º41`W 2286 1925 1962 34°22′N 117°41′W﻿ / ﻿34.367°N 117.683°W
Mount Brukkaros, Namibia Solar 25º52`S 17º48`E 1586 1926 1931 25°52′S 17°48′E﻿ / ﻿25.867°S 17.800°E

Question: How many stations were opened at the Smithsonian Astrophysical Observatory after 1917?

Question: How long has Mount Harquahala been operational, an Arizona station next to the Smithsonian Astrophysical Observatory?

Question: Elevation difference between Mount Montezuma, Chile and Mount Brukkaros, Namibia from the Smithsonian Astrophysical Observatory?