These CRGB filters work best with high-quality reflectors, such as Ritchey-Chrétiens, that are intrinsically well color-corrected. They should be parfocal for systems as fast as f/3.5. The clear (no near-IR blocking) filter in this set may produce bloated stars if your optical system has poor near-IR focus, as is the case with many camera lenses and refractors, which is why this non-near-IR blocked CRGB filter set is generally the best choice for reflector imaging, rather than with less well-corrected refractors or camera lenses.

On the other hand, the near-IR blocked LRGB filter set #TB2LE50R has reduced UV contribution in its luminance and blue filters. This reduces star bloat in optical systems that are not well color-corrected. This makes LRGB filter set #TB2LE50R best suited for imaging with refractors and camera lenses, which often are not particularly well-corrected in the violet end of the spectrum.

A spectral “gap” between approximately 540nm and 640nm minimizes the effect of mercury and high and low pressure sodium city light pollution, as well as several airglow emission lines due to ionized nitrogen in our atmosphere. This gap can be seen in the response curves in the feature image below.

These Astrodon E-Series 50mm unmounted CRGB filters drop into any color filter wheel with filter cups that accept standard 50mm threaded filters, or into the color filter wheel that is integrated into SBIG Research Series cameras. Each is parfocal with Astrodon's high-performance narrowband (H-alpha, Oxygen III, etc.) and near-IR filters, as well as with each other. The filters come individually wrapped in a hard plastic snap-lid storage case.

For more detailed information on Astrodon filters, click on the “Astrodon Generation 2 Filters” icon above.