Mk4 K-Coronameter White Light Polarization Brightness Images

Mk4 is a scanning instrument that provides fully calibrated polarization brightness (pB) images of the Sun's white light corona over a full field-of-view from ~1.12 to ~3 solar radii. Mk4 operated from Oct 28, 1998 until July 20, 2013 when it was replaced by the COSMO K-Coronagraph. Mk4 has a 1-D CCD that acquires a radial scan at a fixed angle every 0.5 degrees and builds up a 360-degree view of the Sun (720 scans) every 3 minutes. Images are available in two formats: 1) original scan format known as 'cpb' images and 2) reformatted (recognizable) cartesian coordinate images known as 'rpb'. The original scanned images (cpb) are 16-bit 720 x 384 pixels with 4.855 arcsec pixels at a 3 minute time cadence. Reformatted rpb images are 16-bit 960 x 960 pixels and keep the solar diameter at a fixed number of pixels, taking into account the change in Earth-Sun distance (i.e. variation in apparent solar diameter) over the year. Data are available on the MLSO web page and can be used to identify and measure coronal mass ejections (CMEs) as well as variations in coronal brightness and structure over the solar cycle.