Narrowband Filters

Today I'm going to talk about narrowband filters, specifically about the false color images they produce. They use filters each for a specific color to give objects a hue and make them visible. Red, Green, and Blue are the three most commonly used as that is the color combination that you see through your tv or computer monitor. These three colors are assigned to a filter that is detected through the narrowband such as OIII, SII, or H-alpha. There are many other filters that are in use, but I name these three because they are the most commonly used for the pictures of objects in space that people view. The first letter of the filter gives you the element that your viewing, Hydrogen (H), Sulfur (S), and Oxygen (O) and what follows is the ionization of the element. H-alpha is very special due to the high amount of emission it creates so it will usually be the main color for the image viewed.

  
For the images I uploaded each uses a different system of filters, the one on top uses what's called HOS which means that H-alpha is displayed in red, OIII is displayed in green, and SII is displayed in blue. This is the most commonly used display for pictures, and this paticular picture is of the Lagoon Nebula. The picture on bottom uses other filters but is a picture of the same thing the Lagoon Nebula, although I am unaware of what filters this one uses.

It is of course possible to use more then three filters, adding extra colors to extra filters, and would change the color of the picture. There are many combinations that can be done, and as the lower image shows, they are not all going to create something that looks nice. So next time you look at a picture of a nebula or some stars, you will know that it's not the color of the object you see, but of what color scheme someone decided to use, and of course you could tell what color they assigned H-alpha as that would be the dominant one.

I credit all this information and the pictures I borrowed from Starizona