Broadband Filter Imager (BFI)

The Broadband Filter Imager (BFI; Table 1) produces photometric images with broad spectral resolution in 6 bands (CN band, Ca II H line, G band, and 3 continuum bands) at the highest spatial resolution available from the SOT (0.0541 arcsec/pixel sampling) and at rapid cadence (<10 sec typical) over a 218" × 109" FOV. Exposure times are typically 0.03 - 0.8 sec, but longer exposures are possible, if desired. The BFI will allow accurate measurements of horizontal flows and temperature in the photosphere, and measurements in the short wavelength bands will permit identification of sites of strong magnetic field.

Table 1. SOT BFI specifications
Field of view 218" × 109" (full FOV)
CCD 4k × 2k pixel (full FOV), shared with the NFI
Spatial Sampling 0.0541 arcsec/pixel (full resolution)
Spectral coverage
Center (nm) Band width (nm) Line of interest Purpose
388.35 0.7 CN I Magnetic network imaging
396.85 0.3 Ca II H Chromospheric heating
430.50 0.8 CH I Magnetic elements
450.45 0.4 Blue continuum Temperature
555.05 0.4 Green continuum Temperature
668.40 0.4 Red continuum Temperature
Exposure time 0.03 - 0.8 sec (typical)

Narrowband Filter Imager (NFI)

The Narrowband Filter Imager (NFI; Table 2) provides intensity, Doppler, and full Stokes polarimetric imaging at high spatial resolution (0.08 arcsec/pixel, somewhat coarser sampling than the BFI) in any one of 10 spectral lines (including Fe lines having a range of sensitivity to the Zeeman effect, MgIb, NaD lines, and H-alpha) over the full field of view (328" × 164"). The spectral lines span the photosphere to the lower chromosphere for diagnosis of dynamical behaviour of magnetic and velocity fields at the lower atomosphere. The passband of the Lyot filter is 90 mÅ and the wavelength center is tunable to several positions in a spectral line and its nearby continuum. It is noted that the edges of the full field of view are slightly vignetted due to the limited size of the optical elements of the tunable filter residing in a telecentric beam. The un-vignetted area is 264" in diameter. Exposure times are typically 0.1 - 1.6 sec, but like the BFI, longer exposures are possible.

Table 2. SOT NFI specifications
Field of view 328"×164" (unvignetted 264"×164")
CCD 4k×2k pixel (full FOV), shared with BFI
Spatial sampling 0.08 arcsec/pixel (full resolution)
Spectral resolution 0.009nm (90mÅ) at 630nm
Spectral windows (nm) and lines of interest
CenterTunable rangeLinesgeffPurpose
517.2 0.6 Mg I b 517.27 1.75 Chromospheric Dopplergrams and magnetgrams
525.0 0.6 Fe 524.71 2.00 Photospheric magnetograms
Fe I 525.02 3.00
Fe I 525.06 1.50
557.6 0.6 Fe I 557.61 0.00 Photospheric Dopplergrams
589.6 0.6 Na I D 589.6 - Very weak fields (scattering polarization)
Chromospheric fields
630.0 0.6 Fe I 630.15 1.67 Photospheric magnetograms
Fe I 630.25 2.50
Ti I 630.38 0.92 Umbral magnetograms
656.3 0.6 H I 656.28 - Chromosphreic structure
Exposure time 0.1 - 1.6 sec (typical)

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