M42 in Hydrogen-α, Oxygen-III, and Sulphur-II; 4th January 2010

Here are wider-angled pictures of M42 taken using my 135-mm SLR lens at f/4 and narrow-band H-alpha, OIII, and SII filters.
(Some earlier pictures using H-alpha and SII only, but which have some merit, are shown here.)

M42 in light from Hydrogen (red), Oxygen (green), and Sulphur (blue). Details of the individual pictures are given below. Move your mouse over the image to see the designations of the nebulae in this picture. Nair al Saif is the central star in NGC 1980.
The picture was made from the three monochrome images below in Photoshop by the method described by Don Waid.
The colours in this image are not what would be recorded by a colour camera (see my earlier pictures). The three narrow-band filters isolate light from three specific atoms. These atoms do not emit light in the blue part of the spectrum; Sulphur emits in the deep red at 673 nm, Hydrogen in the red at 656 nm, and Oxygen in the green at 496 and 501 nm. Thus I have two red pictures and no blue one. It is a matter of choice as to which element is assigned to each of the three chromatic channels that make up a colour picture. I have chosen to make the Hydrogen picture red because this is the main emission from this nebula, and I have made Oxygen green because it is. This left Sulphur for the blue channel despite its light being redder than that from Hydrogen. To see other interesting colour combinations, click on the picture.

M42 in light from Hydrogen. In order to bring out the faint nebulosity the centre has become over exposed.

M42 in light from Oxygen.

M42 in light from Sulphur.

Date and Time 3rd January 2010 22:50 to 23:57 UT

Camera Starlight Xpress MX716

Telescope 135-mm SLR lens at f/4 with Astronomik filters

Capture Star_mx7 90 seconds at full resolution.

Processing Star-MX7: automatic black adjustment, non-linear enhancement 25, automatic black adjustment again. This was applied to each frame individually.
Irfanview: batch conversion to png format.
Registax5: 10 frames stacked, gamma 1.5, histogram 14-255 (OIII and SII) 27-255 (Hα)

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	M42 in light from Hydrogen (red), Oxygen (green), and Sulphur (blue). Details of the individual pictures are given below. Move your mouse over the image to see the designations of the nebulae in this picture. Nair al Saif is the central star in NGC 1980. The picture was made from the three monochrome images below in Photoshop by the method described by Don Waid. The colours in this image are not what would be recorded by a colour camera (see my earlier pictures). The three narrow-band filters isolate light from three specific atoms. These atoms do not emit light in the blue part of the spectrum; Sulphur emits in the deep red at 673 nm, Hydrogen in the red at 656 nm, and Oxygen in the green at 496 and 501 nm. Thus I have two red pictures and no blue one. It is a matter of choice as to which element is assigned to each of the three chromatic channels that make up a colour picture. I have chosen to make the Hydrogen picture red because this is the main emission from this nebula, and I have made Oxygen green because it is. This left Sulphur for the blue channel despite its light being redder than that from Hydrogen. To see other interesting colour combinations, click on the picture.
	M42 in light from Hydrogen. In order to bring out the faint nebulosity the centre has become over exposed.
	M42 in light from Oxygen.
	M42 in light from Sulphur.

Date and Time	3rd January 2010 22:50 to 23:57 UT
Camera	Starlight Xpress MX716
Telescope	135-mm SLR lens at f/4 with Astronomik filters
Capture	Star_mx7 90 seconds at full resolution.
Processing	Star-MX7: automatic black adjustment, non-linear enhancement 25, automatic black adjustment again. This was applied to each frame individually. Irfanview: batch conversion to png format. Registax5: 10 frames stacked, gamma 1.5, histogram 14-255 (OIII and SII) 27-255 (Hα)