The Orion Nebula, M42 and M43 (no unsharp mask)
AAO image reference AAT 19b.     « Previous || Next »

The Great Orion Nebula, M42 and M43,  NGC 1976, ngc1976.jpg, m42.jpg, orion_nebula.jpg
Top left is NE. Image width is about 33 arc min
Image and text © 2000-2010, Australian Astronomical Observatory, photograph by David Malin.

Most of the photographic images from the AAT and UK Schmidt telescopes have been made by combining positive contact copies of three separate black and white plates. These exposures were made to record the red, green and blue light separately. This gives excellent results, far superior to colour film. However, the B&W photographic emulsions used are contrasty and images made from them directly are often uninteresting, like the Orion nebula picture above.

To reveal the detail and structure in the original plates a process known as unsharp masking has to be used. There is more information about this in my technical notes, but basically unsharp masking allows complete control of contrast AND detail rendition in photographic images. The process also now appears in many image processing packages. The picture above was made without unsharp masking, while the images in AAT 19 and AAT 19a were made with the aid of unsharp masks applied to the same plates that produced AAT 19 and AAT 19a.

Related Images
AAT 19.   The Orion nebula
AAT 19a. The Orion nebula (wider field)
AAT 19c. M43, with part of M42
AAT 29.   The Trapezium stars in Orion
UKS 8.    The Great Nebula in Orion
UKS 23.   Faint nebulosity near Orion and Horsehead Nebulae
Constellation of Orion (external site)

For details of photographic exposure, search technical table by AAT reference number.

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Updated by David Malin, 2010, August 1