Here is a new image of Messier 27, done with my new set of Edmund dichroic cyan, magenta, and yellow imaging filters. An alternative to the traditional red, green, blue method, the CMY method has the advantage of allowing more than one color channel through the filter at once making imaging time less critical. At least, that is what it is touted for. This is my first CMY image, and it does appear to do just that. With the old RGB filters, it seemed all I could ever get was red/blue and the green channel was notoriously difficult to get signal with. There are very few, if any, green objects in space, so it would seem that the green color channel is a waste of exposure in many cases. The Cyan filter has both green and blue in its spectral wavelentghs, and in fact pulls in the entire OIII spectral line, which is missed by the old RGB method as this line lies between the blue and green filters.
These filters can be obtained from Edmund Optics and run about $68 dollars a set unmounted.
Yes, they are parfocal! However, I do not believe they block IR.
This image was done using my DSI Pro CCD that I normally use for guiding.