Quote:For example POSS I has red and blue plates, the southern sky survey has red and blue, and POSS II has red, blue, and near IR. They are all available separately, and I have found one amateur taking a very few of them and combining them to make very pretty pictures; but in general I don't see them combined to form color images. They are mostly all available in digital form now. Is it assumed there is no scientific value in looking at them together?
Too many clouds
David Moody, FRAS 17.5" f/5 dob 10" f/10 SCT 5" f/8 refractor 80mm f/6 refractor 66mm f/6 refractor Plus a few others out of the rotation
Quote:Two reasons:1. Before 1960, as everyone knows, all of the world was black and white, so even though they took "red" and "blue" images, they all came out black and white. Attempts to colorize the DSS have been attempted by Ted Turner, but this has met with extreme disdain from the astronomical community.2. What Tony F. said.I've done a few plate combinations synthesizing the green and I know of several who have done this. It is not that hard and you can get some interesting results, though, like Tony mentioned, some of the plates have some problems. One problem I ran into a lot had to do with areas with bright objects or stars or stars near objects. One case in particular, in Fornax, the star right by NGC 1404 is strong in the red making it very bloated on the plate and going into the galaxy, while the blue shows a much smaller star. Synthesized green results can look odd. It just doesn't combine well and requires a lot of post work to make it look reasonable.These plates were not really meant to be combined, but rather they were filtered and calibrated to yield survey data on a stand alone basis for that filter run. That doesn't mean that you can't derive data from the combined images, but the yield would probably be more productive testing against a narrow hypothesis and using other data, as well (such as X-Ray or mid to far IR, for instance).
Quote:There may be a few odd cases where some astronomer might want the R&B superposed for some specific reason, but not often enough to warrant doing them all.
First and foremost observing love: naked eye.
Last but not least, telescopes.
And I sometimes dabble with cameras.