Impact of Ca K filter band pass on the visibility of filaments / comparison with SHG

[Astrochriss]

Hey guys,
I already read this thread a few weeks ago and was really surprised that it is possible to get a view of "only the chromosphere" as long as the bandwidth is small enough, like 0.12A in the paper. I always assumed the calcium concentration in the chromosphere would be too low, so that there is always a lot "photospehere leakage" no matter how small you go with the bandwidth. It is just stunning how similar the view of subframe A) of the paper is to a normal H-Alpha image, showing only the fibrils and no hint of the reverse granulation. I have never seen that before.

Even though we as amateurs probably never reach this crazy 0.12A bandwidth, I would suggest to shift this thread to the reference library. Very usefull stuff here, if someone builds a super-high-(spectral)-res SHG in the future.

Best
Chris

[thesmiths]

Even though we as amateurs probably never reach this crazy 0.12A bandwidth, I would suggest to shift this thread to the reference library. Very useful stuff here, if someone builds a super-high-(spectral)-res SHG in the future.

Actually, I've calculated it would be quite straightforward to achieve 0.09 angstrom spectral resolution at Ca-K using a 3600 l/mm grating. The bigger problem is that is difficult to achieve spatial resolution better than 1.5 arcseconds -- you need extremely good seeing conditions since the image data is acquired serially (and not by "lucky imaging").