Roof Binoculars. Verifying Phase-coating


Staff member
Roof Binoculars. Verifying Phase-coating

Using 2 polarizer filter for the testing
Hold one polarizer filter in a fixed position in front of one of the eyepieces, and hold the other one in front of the corresponding objective lens at the same side of the binoculars. Rotate the polarizer filter at the objective end through 180 degrees , and observe what happens to the image.

If the roof prisms ARE phase - coated (perfectly) , the view will become SLIGHTLY brighter and darker as the lens is rotated .
If the roof prisms are NOT phase - coated , half the image will become darker as if in shadow , while the other half will remain bright.
One way to describe what to expect to see if the roof prisms are NOT phase coated is to imagine looking at a full moon being transformed into a " half - moon ".

(Instructions of KennyJ on Cloudynights forum)

1- Nikon 9x30, produced since 80s, no phase coating

2- Celestron Trailseeker 8x42, have "Phase Coating" on the focus but … you can see it in the movie

3- Swarovski SLC Neu 10x42, produced in 2007, truly phase coating


Ống nhòm dạng roof để đạt độ phân giải cao thường quảng cáo sử dụng phase coating cho lăng kính.
Nhưng tiền nào của đó, cũng là phase coating nhưng ở các ống nhòm xịn mới thật sự triêt tiêu luồng tia phản xạ không mong muốn trên bề mặt lăng kính.
Phase coating là gì ta sẽ tiếp tục ở post sau.