Again this image shows astigmatism with the Omega Optical filter as a BF. In this case an alignment running about 45°, about '10 o clock - 4 o clock'in the image shown can be seen. If you're not used to spotting it minor astigmatism like this might be difficult to recognise but with practice it becomes obvious. It looks similar to aligned rice grains or polished stainless steel.

The image may show astigmatism, but in this case the Ca K filter also picked up minor flaring in the active region AR'1515. Flare activity is more usually picked up in Hydrogen Alpha (Ha) images, but can also be seen in the light of Ca K.