Astromania Focal Reducer f/6.3, Fully Multi Coated Focal Reducer Corrector That Reduces Focal Length & Ratio 37% for Telescope Eyepiece Observing, Work for C Series Schmidt-Cassegrain Telescopes

This is an achromatic (color-corrected) doublet (two lenses glued) that is plano-convex (one flat side, one curved outward).Typically you want to look at (or aim your camera at) the flat side of the lens, yet mine shipped with the curved side facing the male threads/user/camera. I used vernier caliper teeth to gently unscrew the retaining ring and carefully with a cotton pad reversed the lens.After reversing the lens, it went from hazy and distorted to sharp, clear, and color corrected. I’m glad I took a chance on this because it’s a great find and an amazing pairing with my sv205 astrophotography camera with it’s imx415 sensor (only 6mm diameter, but 4k). This helps ‘shrink’ the image coming from the telescope down so more of the telescope’s image and definition fit on the sensor, making a WORLD of difference.If you’re looking at this vs the $10 one – get this. By comparison, the $10 versions: – use a smaller lens, have really bad color fringing, even just for visual use