This filter set is for use with broadband targets, e.g. galaxies, star clusters or reflection nebulae. By balancing the exposure time between all the filters, a final image that represents what normal human vision would perceive if the target were bright enough can be produced.

There is actually no reason not to use this type of filter set for emission nebulae, but they don't allow separation of wavelengths that are close together. For example if shooting a target with both H-alpha and SII signals, both of these would pass through the red filter and it would be impossible to visualise any contrast between them. Similarly, H-beta and OIII signals would be passed by the blue and green filters without any differentiation. It is however still perfectly possibly to produce beautiful images in this way.

Part of the design of this filter set from Antlia is to have a gap between the red and green bandpasses. This gap includes the wavelengths emitted by sodium and mercury vapour streetlights, so in the few places where those are still in use this filter set is effective in removing the effect of that particular source of light pollution.

To see the specific transmission curves of each filter simply hover over the image.

To learn more about this filter set you can visit the Antlia website.