Flattening ChroMag Flat Fielding Solar Images Mara Johnson-Groh - PowerPoint PPT Presentation

Summer 2013 Flattening ChroMag Flat Fielding Solar Images Mara Johnson-Groh Gustavus Adolphus College Alfred de Wijn HAO

ChroMag � Primary Lens � Field Lens � Pre-filter � Lyot Filter � He I – 587.6nm � Camera � Fe I – 617.3nm � Ca II – 854.2nm � H I – 656.3nm � He I – 1083.0nm �

Flattening �

H I – 656.3nm � He I – 587.6nm � Ca II – 854.2nm �

H I – 656.3nm � He I – 587.6nm � Ca II – 854.2nm �

Kuhn-Lin Method � D — image array � G — image gain � x — specific pixel � a — image offsets � n — number of images in series � i,j — specifies which image in series � � Kuhn, J. R., Lin, H., and Loranz, D.: 1991, Publ. Astron. Soc. Pacific 103, 1097. �

Chae Method � Flat pattern � Light level variation � Observed image � Ideal image � Column Adjusts for displacement offsets � boundary effects � Row displacement offsets � Chae, J.: 2004, Solar Phys. 221, 1. �

Model Fit � l 2 nd order polynomial � l mpfit2Dfun � �

Results � H I – 656.3nm � He I – 587.6nm � Ca II – 854.2nm � Fe I – 617.3nm � He I – 1083.0nm � Original flats � Model fitted gain � ol ol ol u u u 0 m m m n ¡ n ¡ n ¡ Chae gain �

Model Deviations from Chae Gain � H I – 656.3nm � He I – 587.6nm � Ca II – 854.2nm � 3.76% � 2.35% � 3.95% � He I – 1083.0nm � Fe I – 617.3nm � 2.43% � 4.32% �