SingAstro

Hi Weixing,

Excellent test results you have posted. This lens is a keeper for both astrophotography and price standpoint.

From my limited experience, the pinkish gradient at the edges is not a result of vignetting, but rather an artifact of LPR front filter. Unlike most camera dye filters, astro filters like LPR, are interference filters by design so as to achieve steep and narrow transmission passband. They conform to specs only at incidence and within a limited range of a cone angle. Beyond the certain angle, the spectral response gradually change due to incremental shift in transmission curve.

Nevertheless the MW looks great under SG skies on previous posting.

Cheers

Matthew

matthew, are you certain the 50mm lens stepped down to a 48mm lpr filter is wide enough to result in what you suggested?
i wonder how will hutech idas filter performed on wide angle lens. it comes in sizes up to 77mm, if i remember correctly.