Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| 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 |
| Mount Saint Catherine, Egypt | Solar | 28º31'N | 33º56'E | 2591 | 1934 | 1937 | 28°31′N 33°56′E﻿ / ﻿28.517°N 33.933°E |
| Burro Mountain, New Mexico | Solar | 32º40'N | 108º33'W | 2440 | 1938 | 1946 | 32°40′N 108°33′W﻿ / ﻿32.667°N 108.550°W |
| Organ Pass, New Mexico | Space Track | 32º25'N | 253º27'E |  |  |  | 32°25′N 106°33′W﻿ / ﻿32.417°N 106.550°W |
| Olifantsfontein, South Africa | Space Track | 25º58'S | 28º15'E |  |  |  | 25°58′S 28°15′E﻿ / ﻿25.967°S 28.250°E |
| Woomera, Australia | Space Track | 31º06'S | 136º46'E |  |  |  | 31°06′S 136°46′E﻿ / ﻿31.100°S 136.767°E |
| Cadiz, Spain | Space Track | 36º28'N | 353º48'E |  |  |  | 36°28′N 6°12′W﻿ / ﻿36.467°N 6.200°W |
| Shiraz, Iran | Space Track | 29º38'N | 52º31'E |  |  |  | 29°38′N 52°31′E﻿ / ﻿29.633°N 52.517°E |
| Curaçao, Netherlands West Indies | Space Track | 12º05'N | 291º10'E |  |  |  | 12°05′N 68°50′W﻿ / ﻿12.083°N 68.833°W |
| Jupiter, Florida | Space Track | 27º01'N | 279º53'E |  |  |  | 27°01′N 80°07′W﻿ / ﻿27.017°N 80.117°W |
| Haleakala, Hawaii | Space Track | 20º43'N | 203º45'E |  |  |  | 20°43′N 156°15′W﻿ / ﻿20.717°N 156.250°W |
| Villa Dolores, Argentina | Space Track | 31º57'N | 294º54'E |  |  |  | 31°57′N 65°06′E﻿ / ﻿31.950°N 65.100°E |
| Mitaka, Japan | Space Track |  |  |  |  |  |  |
| Nani Tal, India | Space Track |  |  |  |  |  |  |
| Arequipa, Peru | Solar,\nSpace Track |  |  |  |  |  |  |
Question:
how many stations opened after 1917?
Answer:
7