Doug Hoffman wrote:
OK, I wasn't sure. I have been surprised at how well I can see with my
ST's in overcast conditions. Better with than without. According to
the maker, "By removing the blue light the eye can more sharply focus
on the remaining wavelengths of light.".

Atmospheric haze scatters mainly blue light. By eliminating shorter
wavelengths you effectively remove/reduce haze and improve visibility.

The above observation is based on my experience with filters in B&W
photography, but I guess the laws of physics are the same for lenses
and canopies ;-)

Bartek