Comparison of Visible and CaK images of sunspots. (6th Oct2017)

Below are 4 pairs of images of sunspots 2683 (large one) and 2682 ( smaller one , only in first two images) taken on 6/10/17. No H alpha was taken as at the end of this sequence high  cirrus stopped any further imaging, in fact last CaK shot is diminished by the entrance of the high cirrus. Experiences of using CaK so far suggests that it brings out more detail in the faculae (bright spots) around sunspots , these are linked to the intense magnetic fields associated with sunspots. The other noticeable effect with CaK is the longer exposure time required, discussion at the IAS suggested that since the filter is double stacked, it requires a Herschel wedge without a ND.3 neutral density filter as supplied by Astrograph ( it’s on my list for Santa!!) , also choice of barlows can be crucial depending on coatings, will see what happens when I’ve tried the new Herschel wedge.

The images are laterally inverted, I haven’t flipped them.

Images are below and are self explanatory.

Pete H

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