Tuesday, 29 July 2014

The Witch's Broom Nebula

Well, after several months of forced inactivity (damn clouds!) I'm back squeezing the small ETX-70. I don't know how much I can extract from this scope yet but I'm starting to think on his replacement. It's a good scope for beginning in astrophotography but now I need more than pea sized stars and destroyed nebulosity by it's halo...

Today I bring the Witch's Broom Nebula or Western Veil or Finger of God or Filamentary Nebula... lots of names for a supernova remnant from 5,000 to 8,000 years ago. This nebula is part of the Cygnus loop, located south the cross of the Cygnus, next to the star Gienah (Eps-Cygni). This supernova expanded its residual dust to cover an area of 3 degrees in diameter (about 6 times the diameter, or 36 times the area, of the full moon). Although the distance to this nebula is not precisely know, it is stimated to be around 1,470 ly (the first Buddha sculptures in Japan were starting to shape when this star went off...)

Even though the nebula has a relatively bright integrated magnitude of 7, it is spread over so large an area that the surface brightness is quite low, so the nebula is notorious among astronomers as being difficult to see. With the aid of special filters (such as OIII) this nebula is easily seen in the night sky but as I'm on a budget, no filters for now...

The image is composed of 43x2' lights (poor alignment and no guiding, originally I had more than 60), 40 bias, 40 darks, 20 flats and 20 dark-flats, stacked with DSS and processed with StarTools (my saviour in this image with its isolate module due to heavy noise from the DSLR).


The annotated image: