A Clear Sky Filter from Optolong Optics Co,.Ltd!
This is a front facing 77 or 82mm, no dark-corner filter. The CSF blocks the city Na and Hg light pollution to improve contrast effectively. The main point of this filter that differs with other light pollution filters, is its front facing, 77 or 82mm, you can twist it into the front of your camera's lens directly like a UV lens.
The performance of this filter reveals no wavelength shifting resulting in no color gradients through the images.
This filter is well suited for use with any lens where a UV lens is recommended.
The images above are from the famous astrophotographer Vincent Cheng of Hong Kong, taken on January 9th.2017.
- The left image was taken without a filter
- The middle image was taken with Optolong Clear Sky Filter single JPEG frame.
- The right image was taken with Optolong's Clear Sky Filter, 62 frames stacked.