The Sun in Hydrogen-Alpha

NEVER point your telescope without appropriate filters towards the sun!

On the previous page I presented the sun in visible light with some sunspots, which could be observed directly with the proper gear.

A visual observation on this last day of February 2026 would have been quite boring, as there were no interesting sunspots.

The image above only shows the Hydrogen-Alpha emission line, so the normally invisible filaments and finer structures became apparent.

Specialized telescopes with, so called, Ethalon filters are commonly used for this type of images. The incoming light is limited to a very narrow range of wavelengths allowing such detailed views. As usual, such instruments are not cheap and only usable for this single purpose.

For this image a different approach was used, which first records the the sun's light spectrum with a Spectroheliograph.  Then this data is mathematically processed by some advanced algorithms.

Generating a Hydrogen-Alpha image is only one option to process this data. Basically any spectral wavelength may be picked to generate an image. This procedure is sensitive enough to detect slight wavelength variations caused by the doppler effect and therefore able to detect movements of the sun and surface structures.

The first image shows several dark areas on sun's surface. These are no sunspots but so called filaments, large streams of matter above the surface, following the local magnetic flux. Often an inverted version of the image is used to gain some clarity. Then these filamens look like floating clouds:

The images on this page were created using the Software JSol'Ex from Cédric Champeau. This piece of art is also capable to determine the sun's coordinate system and annotate known objects. This is kind of impressing:

The annotations expose that I've updated the original images with a versions taken one day later but with better conditions.

In addition to the ready-to-use images presented above, JSol'Ex outputs several raw versions as well, so manual edits may be done up to taste.

I've used the inverted surface image, combined it with a corona image and quickly colorized it. This looked like this: