Sun in Ca II k line – 5th May 2013


There was a 20 minute gap in the clouds this afternoon, and having worked out how to swap out the internal filters within the Baader Herschel wedge, I removed the 2″ Solar Continuum filter and added aBaader  Calcium-k line 1.25″ filter to the nose of the DMK.  Only managed a couple of very short AVI’s before the cloud won, so the image is a bit noisy stacked 300 frames from 660 taken.

Sun 5th May 2013


The Baader Calcium K libe filter has an 8nm bandpass centred around 395nm.  The Calcium k line is emitted from the low to mid chromosphere of the sun.  The Calcium K line emission is very sensitive to magnetic fields.  If modeerately strong magnetic fields are present, the absorption is much less and the area appears brighter in the image, very strong magnetic field show up as very dark areas (such as sunspots).

Through the Calcium K line filter chromospheric faculae can be seen across the whole face of the sun and can usually be used as a predictor of future sunspot activity.  It can be seen from the photo above how the chromospheric faculae exists in two distinct bands across the face of the sun.

Thanks for looking