MikeM I was reading mixed messages and this helps clarify.
This is why I mentioned an uninverted frame.
Starting from the top left corner of an uninvited frame, the Bayer filters take an RG/GB pattern that I showed. The origin at top left is the most common coordinate system used by computer graphics types.
However, some people references an image from the bottom left of the image, upwards, like what is commonly used in Physics, then the pattern for a sensor with an even number of vertical pixels becomes:
GB
RG
or more commonly known as GBRG.
So, both are correct; you just have to know the coordinate system that the program is using. The main problem is that most programs don't tell you what they use, and you have to discover it by trial and error. Documentation for a lot of hobbyist astronomy is abysmal.
Moreover, there are color sensors that are manufactured by various companies that uses a different pattern that Sony favors, some of which are even arranged in other shapes than a 2x2 square
Foveon CMOS sensors do not even have a sub-pixel pattern (every photo site of the Foveon sensor have full resolution R, G and B components), but their red and blue sensitivities are much lower and thus not suitable for astrophotography.
Except for the ASI120 line, ZWO appears to like to use Sony sensors, so with newer ZWO cameras (the one that uses sensors with IMX prefixes -- for example, Sony IMX071 is used in ASI071MC, Sony IMX462 is used in ASI462MC), it is safe to use RGGB with programs that references its pixels from the top left corner of a frame.
For what its worth, RGGB is one example that was given in Bryce Bayer's Kodak patent, from which "Bayer pattern" is named.
Chen
