The Sun imaged in the near UV: Daystar Calcium H-line Quark vs Baader K-Line filter

sun20170820FD_CaH

When I started observing the Sun on a regular basis, several decades ago, amateur astronomers were involved mainly in drawing and counting sunspots, in calculating the Wolf number and in following the evolution of solar cycles in white light. The “solar telescope” by definition was a small refractor with a … Continue reading