Digitized Archival Data: 1904 onwards

The Kodaikanal observatory has been obtaining solar images since 1904 in broad band white light, narrow band Ca-K 393.37 nm and Hα 656.3 nm wavelengths. Many of these observations are still continuing. The historical data which were on photographic plates has been digitized. The first level calibration of the Ca-K, white light and Hα images have been completed and the data is now available through this portal. Final calibrated images and the data will be posted on this site in near future. The data availability and statistics are provided at the bottom of this page.

The digitised data are available for use by the scientific community. If you are interested, please write an email to dipu AT with a copy to diriia AT

Database details:

Description of the different data levels:

level 0a: Raw images with three qualities (good, normal and bad). Dark is subtracted during Digitisation.
level 1a: Flat, bias corrected, Disc centred, rotation corrected with non-uniform radii with three qualities (good, normal and bad)
level 1b (LDC): Limb darkening corrected disc centred image with uniform radii.

Digitisation team

Twin Telescope Data: 2008 onwards

CaK and white light

Data from Ca-K line (Sun as a star)

Sun as a star using Ca-K line observing program was started in the year 1969 by Vainu Bappu in Kodaikanal Tunnel Telescope. Refer paper Sivaraman et al (1987ApJ...313..456S) for more details. In 1986 the technique of observing at different solar latitudes and integrated over visible 180 degree longitude using Ca-K line profile was initiated. We have latitude data taken from 1989 - 2011, for some days. Sun as a star data also have been taken. Using the latitude data and Sun as a star data, integrated data were derived using quadratic fit. The definition of Ca-K line parameters were as described below, K1 width: K1 width is defined as the wavelength separation between the K1v and K1r minima. K2 width: K2 width is defined as the wavelength separation between the K2v and K2r emission peaks.