Utah Skies: Colors Of Astronomy

Aug 24, 2021

The following is an unedited transcript:

Credit Bruce Horrocks

My wife will often say that astronomy is a deceiving hobby.  When you look at something through a telescope lens you never see the same object as it appears in pictures you will see in magazines or web articles.  Even the great Orion Nebula with its beautiful array of red to purple looking dust clouds looks grey and fuzzy in most telescopes.  And when you look at Hubble Telescope images, they are never shown in the objects true color.  So why such a difference? 

The visible spectrum of light for must of us is between the wavelengths of 380 to 750 nanometers.  This includes all the colors in rainbow from red to violet.  Colors below 380 nanometers are ultraviolet and those above 750 are called infrared. The Hubble Telescope is able to capture some of the light beyond the spectrum of what the human eye is cable to see.  The Hubble cameras also limit the wavelengths of some light to a very small band width which is referred to as narrowband images. Many of these colors would be hard for the normal human eye to distinguish one from another.  NASA scientist then use some artistic ability to assign some these colors to another shade that our eyes will recognize. 

Therefore, some infrared colors will be assigned to red, some to green, and others to blue.  By mixing these colors together we are able to get the beautiful green, blue, and yellow colors in the Hubble images, that otherwise would appear to us as mostly red.  This changing around the colors produces an image with greater detail and reveals some intricate results.  This same procedure can be done by amateur astronomers as well using various narrowband filters to help eliminate unwanted light.