1. Chromosphere Filters
Kathy Geise

2. Fabry-Pérot Etalon/Interferometer
Sodium
vapor lamp
Fabry-Perot interferometer
Sodium doublet
Sodium D-lines are at and nm

3. Fabry-Pérot Etalon
Light enters the etalon and undergoes multiple internal reflections.
The transmission of an etalon is a function of wavelength
A high finesse etalon has sharper peaks than a lower transmission etalon.

4. Resolvance Resolving sodium D-lines requires a resolvance of 1000.
Emission spectrum
Resolving sodium D-lines requires a resolvance of 1000.
Resolving hydrogen and deuterium requires a resolvance of 3300.
Often done by a Fabry-Pérot interferometer because it is high resolution device.

5. Fabry-Pérot Interferometer
A picture of the solar corona taken with the LASCO C1 coronagraph, aboard the SOHO satellite, which employed a tunable Fabry-Pérot interferometer to recover scans of the solar corona at a near the FeXIV green line at nm.
The picture is a color coded image of the doppler shift of the line, which may be associated with the coronal plasma velocity towards or away from the satellite camera.

6. The Solar Chromosphere
The chromosphere is about 8000 km thick.
It is a transitional layer between the photosphere and the corona.
Hydrogen alpha emission line is at nm.
Calcium K line is at 393.3nm.

7. Anatomy of an HA filter system
An ERF or Energy Rejection Filter blocks unwanted UV and IR wavelengths.
The Etalon passes the desired wavelength.
A blocking filter further tunes the system.

8. Commercially available HA filter systems
DayStar
Solar Spectrum
Coronado, now Meade

9. Coronado Solar Filters Irvine, California
Balboa Island
M.B.A UC Irvine
Newport Beach

10. Credits The Sun imaged in the UV by TRACE