This is the Tulip Nebula (Sh2-101, LBN 168), an emission nebula in Cygnus. The team did this target in October 2021 but since then the equipment has been upgraded, and hopefully my skills have been upgraded also. The old version was in the HOS palette. At the time I was not really liking the SHO palette. It has since grown on me and it’s usually my starting point now for narrowband images. I did try this in a Foraxx palette which approximates natural colors with narrowband data and that looked well for the actual “tulip” but the faint wispy outskirts were faint red on black background and I couldn’t find a way to enhance that in a way that looked good. And SHO looked really good also, especially when the hydrogen-alpha green was toned down.

For those that don’t know, SHO (also known as the Hubble palette as it was popularized by images from that telescope) put sulfur II in the red channel, hydrogen-alpha in the green channel and oxygen III in the blue channel. While the actual color of S II is red and O III is a teal, hydrogen alpha is also a shade of red and not remotely close to green. This is why almost all nebula look red in a natural view. Hydrogen-alpha emission dominates their light output and so the nebula looks red. Using narrowband filters let’s use tease out the fainter S II and O III emission and enhance them to make the differences in structure in the nebula more apparent. It is definitely not at all how the nebula would look in real life. But, it lets us see things that we couldn’t see directly with our own eyes. In a pure SHO image you can make some judgements about the composition of the nebula by the color combinations but since the green from the hydrogen emission is so much stronger than everything else many SHO images (including this one) would be overwhelmingly green and not very pleasant to look at. In this case I took about ¾ of that green out to create a more pleasing image.

The Tulip Nebula is about 6,000 light years away. The bright tulip-like part of the nebula covers an area of the sky that is 16 arc minutes by 9 arc minutes. For comparison the moon covers an area of roughly 30 x 30 arc minutes so you would be able to get roughly 6 tulips inside the area of the full moon.

This is 18h 45m of SHO data plus 6h of RGB for stars. For all the processing details, see astrobin.