I wanted to be able to view the sky and planets using different wavelengths of light, and a convenient way to achieve this was by the use of "filters", as shown below in Figure 1.
This enables me to either adjust the camera orientation while keeping the filter in fixed position, or move the filter around a while keeping the camera orientation fixed (or a combination of both), and see the relevant portion of the sky in a different wavelength. By ajusting the opacity scale it is possible to see how items relate to each other in different wavelengths (for example an area of H-Alpha emmision originating from particular star or deep-sky object in the visible spectrum).
The approach I am currently taking is to render the view in each wavelength, and create opacity masks which I can use to blend the views together. In this way I can use multiple filters of arbitrary shape and size.