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Table 1.
Parameters of spectrograph gratings used during the lifetime of project.
| No. | Start date | Grooves | λ | m | s−1 | Scale (a) | Measured and true (b) field strengths (G) | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| mm−1 | Å | mm Å−1 | 100 G | 100 | 1000 | 2000 | 3000 | 4000 | |||
| 1 | 1917 | 602 | 6173 | 2 | 2.97 | 1° | 90 | 920 | 1900 | 3010 | 4320 |
| 2 | 1930 | 602 | 6173 | 2 | 2.97 | 1° | 90 | 920 | 1900 | 3010 | 4320 |
| 3 | May 1949 | 400 | 6173 | 3 | 2.96 | 1° | 90 | 920 | 1900 | 3020 | 4340 |
| 4 | 29 Sep. 1950 | 400 | 6173 | 3 | 2.96 | 1° | 90 | 920 | 1900 | 3020 | 4340 |
| 5 | 19 May 1955 | 600 | 6173 | 2 | 2.96 | 1° | 90 | 920 | 1900 | 3020 | 4340 |
| 6 | 22 Aug. 1960 | 600 | 6173 | 2 | 2.96 | 1° | 90 | 920 | 1900 | 3020 | 4340 |
| Same (c) | Oct. 1961 | 600 | 5250 | 5 | 11.15 | 0.5° | 90 | 940 | 2180 | 4050 | … (d) |
| 7 | 24 Dec. 1962 | 610 | 5250 | 5 | 11.66 | 0.5° | 90 | 900 | 2080 | 3870 | … (d) |
| 8 | 17 May 1982 | 632 | 5250 | 5 | 12.96 | 0.5° | 80 | 810 | 1870 | 3480 | … (d) |
| 9 | 21 Nov. 1994 | 367.5 | 5250 | 9 | 15.27 | Table 2 | … (e) | 760–800 | 1880–1940 | … (e) | … (e) |
Notes.
(c)
Grating No. 6 was used from 22 August 1960 through 23 December 1962. In October 1961, the wavelength for sunspot observations was changed to Fe I 5250.217 Å.
(e)
Out of range of lookup Table 2.
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