How bright is the [Si X] 1431 nm coronal emission line?

Airborne eclipse observations of the Six] 1430.5 nm coronal emission line are reviewed, and new ground-based out-of-eclipse coronagraph observations obtained at NSO/Sacramento Peak are reported. We find that the Six] 1430.5 nm coronal emission line brightness is less than 8 × 10⁻⁶ B⊙ in small active region corona which showed Fexiii] 1074.7 nm emission (corrected for sky background) of about 20 × 10⁻⁶ B⊙. Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.