The red and blue images are combined to to make RGB color. The green channel is usually a 50-50 combination of the red and blue.
Some additional processing is done to enhance the resulting color images.
Unless indicated otherwise, gray scale images that appear on these pages are obtained from the digital sky survey at SkyView . Basic object information, eyepiece simulations, and general finder charts are derived from our SkyTools observing software. There are also links to professional publications on these sites which can often be found on line. Burnham, Robert Jr., Burnham's Celestial Handbook , Dover Publications, Inc., New York, 1978. Houston, Walter Scott, Deep Sky Wonders , Sky Publishing Corp., 1999.