User:Graeme Bartlett/spectrum of calcium

The spectrum of calcium includes Fraunhofer lines due to neutral calcium and singly ionized calcium (Ca II) in the ultraviolet. The violet G line includes neutral calcium absorption at 430.774 nm, but also includes neutral iron. The K line is at 393.368 nm and the H line at 396.847 nm.

Applications
Solar observations can make use of narrow filters that only allow the H or K line through. For example the Dutch Open Telescope has used the H line filter. The H line is close to the hydrogen ε line (or is this Hδ on 410.175nm?) and so is not used so much as a K line filter. Using the K line calcium plage can be imaged on the sun.