<Sodium also shows impulsive-phase flare eruption kernels. Na D is a low excitation line emitted when the low chromosphere is heated, usually at footpoints of flux loops passing through a flare, as sodium D line reflects the lower chromosphere. Visual and photographic images reveal type image as Calcium, revealing granulation, but are much brighter and more easily visible.
University series filters are designed to operate unheated on the lower of the two Na D emission lines; and can be heated to accomplish transmission on the higher of the two Na D lines, making doppler studies possible by photographing in each line and derriving difference images after subtracting an average solar velocity image. This process is referred to as a dopplergram velocity image, reveals the surface motions associated with supergranulation.
Mount Wilson Solar Observatory
These filters have until now been primarily used for research purposes only, performing doppler and supergranulation studies. Narrow bandpass Na D line filters have also been used in deep-sky observations of IO, but with significantly larger apertures.
DayStar Sodium Filter assemblies
||0.4Å Single cavity Amateur T-Scanner filter system
$4500.00 after instant rebate
- suitable for visual or photographic observing
|0.4Å Single cavity University series filter system
$7038.00 after instant rebate
- suitible for photographic and visual observing