My Maxim DL program -- which I used to process my M22 photo -- has a place to click for white balance and another for color balance. It also has an auto-balance feature. What I'm thinking now is that the original exposures have the information needed for true color, but I clicked on the wrong star to set the color or white balance; or I told it to do it automatically, and that was a mistake. (I tried to process several different ways and I'm not sure which I ended up with). I suspect that with the correct processing I could get something close to true color for M22. Long ago I took a film photo of M13 and it turned out almost pure blue -- why did that happen? Best wishes, Joe --- On Sat, 6/13/09, daniel turner <outwest112@yahoo.com> wrote: From: daniel turner <outwest112@yahoo.com> Subject: Re: [Utah-astronomy] M22's Blue Stars (continued) To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Date: Saturday, June 13, 2009, 1:21 AM There is a long sad story that goes with this debate. Several years ago when astrophotography was starting to catch on in amateur circles there was a vigorous debate about whether pictures should reflect reality of the science or be interpreted solely for their beauty. The science side held the moral high ground but over time were swamped by events in the market place. The software vendors have no sympathy with scienctific realism and they install auto whitebalance routines all along the chain of processing. Starting with antiblooming gain on the chip and the color masks of popular DSLR cameras through the conversion to JPEG and into the world of photoshop. It is extremely difficult to get an accurate color balance with amateur equiptment. When it is achieved with much effort and special equiptment the results are less "pretty" than most people want to see. For the science, we know the color of M22 by brute force analysis of individual stars. lots of them. There are no vast populations of blue stars in the cluster. http://www.slas.us/gallery2/main.php?g2_itemId=2033 We know where the mainsequence cutoff is, it is redish, and you can see the spinkle of blue stragglers to the left of that. This is the reality of M22, the science. DT _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com