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Table 1.

Calibration factors.

Channel Hα (l1) Ca II (l2)
Central filter wavelength λ (nm) 656.28 393.37
Equiv. filter bandwidth Δλ (nm) 0.050 0.25
Im(λ) above atm./W m−2 nm−1 0.36 ± 0.02 0.33 ± 0.07
Im integ. through filter/W m−2 0.018 0.083
K solar surf./kW m−2 nm−1 sr−1 529 ± 30 485 ± 90
Lm solar surf./kW m−2 sr−1 26.5 ± 1.5 122 ± 26

Notes. First pair of lines: specifications of our filters. Middle: irradiance from the calibrated solar spectrum in blue from Fig. 6, integrated over the transmission curve. Bottom: calibration factors.

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