HAO Colloquium Series presents Shibu Matthew, Udaipur Solar Observatory

Solar imaging using Fabry-Perot etalons

Measurement of magnetic and velocity fields on the Sun is the key to understand the solar activities. Recently, there exist several projects which are dedicated for high resolution observations of these quantities. The major techniques for measuring the magnetic and velocity fields involve spectroscopy, which could be done using a high resolution spectrograph or using a tunable narrow band filter in an imaging system. Conventionally, narrow band-imaging is achieved by birefringent Lyot filters, which are wavelength tunable, but can be slow due to the mechanical movements involved in the tuning process. Using fast tunable narrow band filters two dimensional images could be obtained while scanning across the spectral lines within short time periods. Two dimensional images with the spectral information provide enough opportunity to apply inversion techniques to retrieve the magnetic and velocity fields. Some of the recent instruments use Fabry-Perot etalons for achieving narrowband imaging, specifically with solid state etalons made of lithium niobate substrate.  Solid state lithium niobate etalons provide a better field-of-view advantage than the air-spaced etalons for the same clear aperture. In this presentation, I discuss  the test results of a narrow band imaging system being developed using two lithium niobate etalons. The imager will be used as a back end instrument with a Multi Application Solar Telescope (MAST), which is being installed at the lake site of Udaipur Solar Observatory (USO), India. Along with a polarimeter, the imager will be used for measuring the magnetic and velocity fields of sunspots and active regions in the solar photosphere and chromosphere.

Date and time: 
Wednesday, August 28, 2013 - 3:00pm to 4:00pm
2139 Captain Mary