Tulip Nebula, aka Sharpless 101 (Sh2-101), is a H II emission nebula located in the constellation Cygnus. It lies at a distance of about 6,000 light-years from Earth. The Tulip nebula is in close proximity to Cygnus X-1, site of one of the first discovered black holes. Cygnus X-1 is out of the frame, but the bow shock created by the black hole may be visible.
As usual, RGB is intended for starfield purpose to support SHO, yet RGB was made deep enough to be processed as a standalone color image.
Here are some comments from George, who processed the image above in RGB: the image shows a very prominent diffraction spike coming from the nearby magnitude 3.85 star HD 188947 (in the image above, the spike was attenuated for aesthetic reasons). It is suggested to use a modern separation of starfield/background (ie: Starnet or StarXterminator), then address the spike on the background frame and merge back to obtain a more eye pleasing image. LRGB using synthetic luminance may also improve the result. This RGB image is not very deep by Moana’s standards (5 hours of exposure for RGB) but benefited from a very dark sky and no moon.
The narrow band data is a bit challenging to process, as Ha is very bright, while SII and OIII are pretty weak.
The SII on the original data was not dithered enough (telescope pilot oversight), and after stack it showed a slight walking noise. So after I became aware of the problem I shot some additional SII since the target was still well placed. This is the reason for the 3rd dataset (Tulip_SII).
