Review on 📸 Samyang SY300M-MFT-BK 300mm F6.3 Mirror Lens - Optimized for Olympus Pen and Panasonic Interchangeable Lens Cameras by James Mayfield

I bought this lens for astrophotography and I think it works fine. I needed a high magnification lens for my 4/3 micro camera (Olympus E-PL5) which I put on a polar telescope. On the first night I took and stacked 11 two-minute exposures of the small star cloud in Sagittarius, M24. The stars had some distortion in the corners and some vignetting in the middle. But the angular distortion was barely noticeable and I corrected the vignetting with flat frames. I don't have much experience in piggyback astrophotography and I have no experience with SLRs. Experienced astrophotographers may have higher expectations of the capabilities of this lens, but for my purposes it's very good and reasonably priced. I am satisfied with the picture quality. I calculated that the effective aperture of this lens, after subtracting a small secondary obstruction in the center, is about 45 millimeters. This was enough to get good shots of the M24 starfield, which could be stretched in processing to get a good image. So far I would use the Hyperstar lens for the M24. Instead of using a camera lens outside the telescope, Hyperstar uses a telescope mirror to collect light. The Hyperstar approach collects much more light, but the coma effects with my telescope are much worse than the relatively small angular distortion of the Samyang lens. I look forward to using this lens for more astronomical purposes.