Hi Sara
The ratio depends on how much of each wavelength is present. The Ha is always strongest so has a value of 1 and then it depends on how much OIII and SII is present as to what ratio is used, sometimes it is a bit trial and error. Currently I am working on different processing techniques to get around this by stretching the histograms for each channel separately in order to equalise them before colour combining
Regards
Gordon
Sara
24-Jun-2012 18:43
Hi Gordon, I noticed that you used a ratio of 5:1:7 for your NB ratio. Can I ask how you decided on that ratio? Regards