Abell 21 - The Medusa Planetary Nebula in Gemini

[Laurin Dave]

Imaged over the nights of 4,5 and 8 January through my Esprit150SX46 and Esprit100ASI1600 dual rig.  3hrs each RGB through the 150, 9 hrs Ha split equally between the scopes and 8 hrs of Oiii through the 100.  Processed in Pixinsight and Photoshop.   The Medusa nebula is about 1500 light years away , 4-5 light years in extent and pretty dim with surface mags estimated at between 16 and 25.. Discovered in 1955 by George Abell who classified it as an "Old Planetary Nebula".  Named after Medusa as the filaments are supposed to represent the Gorgons hair.

C and C welcome.. thanks for looking

Dave

 

[Craig a]

Super image and the faint extended nebulosity is showing, will I turn to stone if I look too long?

[geeklee]

That's excellent Dave.  As mentioned above, the OIII getting fainter and fainter plus that elusive and almost "not there" Ha even further out (and in the bottom left of the nebula) shows superb processing. 

[gorann]

A great capture and excellent processing Dave! As said you caught even the faintest parts.

[Laurin Dave]

44 minutes ago, gorann said:

A great capture and excellent processing Dave! As said you caught even the faintest parts.

 

16 hours ago, geeklee said:

That's excellent Dave.  As mentioned above, the OIII getting fainter and fainter plus that elusive and almost "not there" Ha even further out (and in the bottom left of the nebula) shows superb processing. 

 

17 hours ago, Craig a said:

Super image and the faint extended nebulosity is showing, will I turn to stone if I look too long?

Thanks all..  I find that masks are the key to including the dim stuff without introducing noise into the background.  I made starless version of the Ha and Oiii, then made range masks from them  in Pi then adjusted the masks in Photoshop and used them when adding the Ha and Oiii using blend mode lighten in Photoshop..  

[gorann]

1 hour ago, Laurin Dave said:

 

 

Thanks all..  I find that masks are the key to including the dim stuff without introducing noise into the background.  I made starless version of the Ha and Oiii, then made range masks from them  in Pi then adjusted the masks in Photoshop and used them when adding the Ha and Oiii using blend mode lighten in Photoshop..  

I use a similar procedure. First I stretch the image until I see what I have got. Then I use Star Xterminator on it and polish off any remaining star traces (Dust & Scratches filter on small things and clone stamp or spot healing on bigger ones). I then stretch the nebulosity until I like what I see or hit the noise. Finally I put the original image back as a layer in blend mode lighten and use a curve on it to bring out the stars to an acceptable degree. The latter takes a bit of fiddling with the curve to avoid dark ringed stars.

[FranckiM06]

Wow, it is excellent result and wonderful image.