April 2026

Welcome to Hank’s April 2026 Astrophotography Blog. This month the skies outside of Custer, South Dakota opened up enough to capture a few things in the night sky. First up is the Sunflower Galaxy. You may recall that I’ve been switching from using Siril to using PixInsight software to process my images. Even after nearly 5 hours of light capture the Sunflower Galaxy didn’t show much detail when I processed it in Siril, so I ran the finished Siril image through PixInsight, and it seems to reveal features not seen in Siril. Here they are side by side for you to compare:

Here are two other “local” images that I processed in PixInsight:

The remaining images I acquired through my subscription with Telescope Live. They are images taken from around the world, in some of the darkest sky areas left on Earth–Chile, Spain, Australia…. They have several very large professional telescopes at these locations and make their images available to folks like me who will never have a telescope set up on a Bortel 1 desert mountain top in Chile. All of these images were taken in Bortle 1 skies. Bortle is the scale of light pollution, with 1 being no light pollution to 9, which is like New York City. Where I live outside of Custer, South Dakota, it is a Bortle 4. BHAS members recently went to find our closest Bortle 1 area—it was in Montana. There, you can see stars all the way to the horizon, and all the way around the horizon. They reported that the Milky Way casts a shadow on the ground at that Bortle 1 area!

All of these images were taken in the Southern Hemisphere. The Ha, L, R, G, B labels show the filters that were used to capture the images. Ha detects the hydrogen emissions, L the Luminescence (non-filtered light), and the R, G and B stand for the Red, Green and Blue filters that were used. We cannot see Ha emissions, but the filter can help us detect it, and in processing we assign the Ha emission to a color we can see, like Red, Blue or Green. They add details that RGB filters cannot detect. These filters are used with mono cameras or cameras that have only one sensor. My camera is a “one-shot-color” camera, that has 4 sensors to pick up the different colors (Red, Blue and two Greens) so RGB filters are not needed. I’m really having fun processing these photos, but the learning curve is still a little steep for me with PixInsight. My favorite of the bunch is the Antennae Galaxies. These are two galaxies that are swinging around each other because they are gravitationally drawn together.

Until next time, Clear Skies! -Hank