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

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

Jun 29, 2023 526 likes •672 views

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

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SLIDE 1

Flattening ChroMag

Flat Fielding Solar Images

Mara Johnson-Groh Gustavus Adolphus College Alfred de Wijn HAO

Summer 2013

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ChroMag

  • He I – 587.6nm

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

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SLIDE 3

Flattening

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He I – 587.6nm Ca II – 854.2nm

H I – 656.3nm

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H I – 656.3nm

He I – 587.6nm Ca II – 854.2nm

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Kuhn-Lin Method

  • Kuhn, J. R., Lin, H., and Loranz, D.: 1991, Publ. Astron. Soc. Pacific 103, 1097.

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

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SLIDE 7
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SLIDE 8

Chae Method

  • Chae, J.: 2004, Solar Phys. 221, 1.

Ideal image Light level variation Flat pattern Observed image Adjusts for boundary effects

  • Row displacement
  • ffsets
  • Column

displacement offsets

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SLIDE 9
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Model Fit

  • l 2nd order polynomial

l mpfit2Dfun

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Results

  • l

u m n ¡

  • l

u m n ¡

  • l

u m n ¡

Ca II – 854.2nm He I – 587.6nm Fe I – 617.3nm H I – 656.3nm He I – 1083.0nm Original flats Model fitted gain Chae gain

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SLIDE 13

Model Deviations from Chae Gain

  • 2.35%

3.95% 3.76% 4.32% 2.43%

Ca II – 854.2nm He I – 587.6nm Fe I – 617.3nm H I – 656.3nm He I – 1083.0nm