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Cameras: Color or Monochrome

Some dedicated astrophotography cameras come in color (known as One Shot Color or OSC) and monochrome (black and white). Monochrome cameras are typically more sensitive than OSC cameras. The reason has to do with the Bayer matrix. A bayer matrix is a grid of tiny filters that send one color of light to a pixel (red, green and blue). The camera's internals then convert adjacent pixels into a color value. They are considered less sensitive because you reduce the number of pixels available to a particular object that might only show up in one color. So, for example, if the object you were imaging was primarily visible in the red wavelength, the light would get filtered out when passing through the blue or green portion of the bayer matrix. So the pixels under those other filters would see very little. The advantage of a OSC is that you get the image in color with one shot. One shot color cameras also tend to be less expensive. Since more people want them, more of them are made and their cost goes down. Monochrome cameras are more of a niche product so they don't make as many.

In contrast, monochrome cameras have no bayer matrix so all of the red wavelength could hit every pixel on the sensor. The major disadvantage of a monochrome camera is if you want color, you have to put a filter in front of the camera and take three separate shots (one red, one green, and one blue). You then need to combine those images through software to get a color image. For video astronomy, if you wanted color with a monochrome camera, the only option at this time is a Starlight Xpress camera. The software used to view it live (Starlight Live) has the capability to assign an image to a particular color channel. It still requires changing the filter and taking three separate images so it will take a bit longer. But it is possible to do it on the fly through the use of filter wheels. Monochrome cameras also offer the possibility of doing near live narrowband imaging in multiple colors.

Below is an image of M1 (also known as NGC 1952, the Crab Nebula). This is a near live narrowband image I took with an 8" Newtonian telescope, the Lodestar X2M and some Orion Ultra-Narrowband filters. The filters limit the light to only Sulfer (Red), Hydrogen (Green) and Oxygen (Blue) emission lines. Sulfer and Hydrogen are normally in the red portion of the spectrum but I've manually set hydrogen to Green to show the detail.

This is M1 shot with the Ultrastar C (OSC) in the same 8" newtonian.

#videoastronomy #cameras


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