Baader Semi APO Filter 20244 the price therefore initially may

the price therefore initially may appear high for "nothing more than" a clamping device

"Refractors have long been coveted by many observers since the unobstructed optical system offers high contrast views much prized by lunar and planetary observers as well as many aspects of deep-sky viewing

giving imagers the option to shoot at ultra-fast f/2

allowing you to change eyepieces without requiring you to remove and re-attach the filter from each eyepiece barrel

The Nikon T ring fits 99% of  Nikon DSLR cameras including the following:

Baader Semi APO Filter 20244 the price therefore initially mayPlanoptically Polished with Phantom Coating Group (PCG). Baader's newest addition for Achromat owners. The Semi APO works like it's name implies delivering an amazingly neutral view, while cutting most of the annoying and contrast robbing violet fringe that plagues all achromats. The Semi APO filter combines a stronger Fringe Killer coating formula with the Moon & Skyglow Neodymium substrate. The result is similar performance to the Fringe Killer +