VizieR Online Data Catalog: Polar network index for the solar cycle studies (Priyal+, 2014)
Abstract
The spatial resolution of the Ca K spectroheliograms taken at Kodaikanal (hereafter KKL) is about 2 arcsec and the exit slit of the spectroheliograph yields a spectral window of 0.5 Å centered at the Ca-K line at 3933.67 Å. Ermoli et al. (2009ApJ...698.1000E) pointed out that the Kodaikanal archive hosts the longest homogeneous record, with fewer variations in spatial resolution. The earlier version of the 8 bit data at Kodaikanal is sufficient to study those plage area with high intensity contrast, but does not provide the required photometric accuracy to properly identify the network structures because of the small intensity contrast of these features. Therefore, we have designed and developed two digitizer units, using a 1 m labsphere with an exit port of 350 mm which provides a stable and uniform source of light with less than 1% variation from the center to the edge of the light source. The CCD camera with 4kx4k format, a pixel size of 15 u square, and a 16 bit read out, operating at temperature of -100°C, was used to digitize the images. The Ca-K network can be clearly seen because of the high spatial resolution of digitization (0.86 arcsec).
(4 data files).- Publication:
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VizieR Online Data Catalog
- Pub Date:
- April 2017
- DOI:
- 10.26093/cds/vizier.17939004
- Bibcode:
- 2017yCat..17939004P
- Keywords:
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- Sun;
- Magnetic fields;
- Solar system