The Bat and Squid Nebulas from Germany
Here's a photo from a friend, Pete, who lives in Germany. It's a story of collaboration between different objects.
Peter got into astrophotography in 2014, and has steadily developed has talents and equipment ever since. Like most of us, he started with a DSLR, but now uses a dedicated astrophotographic sensor. He also has two triplet refractors that he uses from a fixed pier.
The first collaboration is the object itself. Clearly, there are two separate structures here. The red nebula is Sh2-129, or the Flying Bat. The blue nebula is the very recently (2011) discovered Ou4, or the Squid.
Apparently, both occupy the same area in space - one is not behind the other. The only sad part is that you can't see any of this from Australia.
The Squid Nebula gets its shape from jets from the triple star system in its middle. The blue shock-waves are rich in ionised Oxygen, which is very dim. It's no surprise that the Squid was only discovered in 2011. In contrast, the Bat is very bright in the more common Hydrogen.
The second collaboration is Pete's method of capturing this image. This, to me, is as wonderful as the nebulas themselves. Astrophotographers are used to replacing stars in narrowband images, but this image is essentially three different components on top of each other.
The red image (the Bat) was shot using an 80/480mm wide-field scope with a filter that is sensitive to ionised Hydrogen. The image is a stack of 80 of exposures of 200 seconds each.
To get the very dim blue (Squid) image, Pete used the larger (130/910mm) scope and also longer (300s) exposures, using a filter for ionised Oxygen.
Narrowband images give stars a pink colour, so Pete used a small stack of 30 second exposures through red, green and blue filters to isolate them.
To arrange the final image, Pete positioned the nebulas as a background, then removed the pink stars using Starnet++. Then he added in the nicely coloured stars.
For a technical challenge, this photo was off the charts!