This actually is not just an ocular thing, could be implemented - as option! - also for regular zooming. However, decreasing color intensity requires some non-trivial shader in the right place. (At least RGB->HSV, desaturate, HSV->RGB; or even taking scotopic vision into account) And: Usually telescopic observers switch to night mode (red-only)... :-)
This actually is not just an ocular thing, could be implemented - as option! - also for regular zooming. However, decreasing color intensity requires some non-trivial shader in the right place. (At least RGB->HSV, desaturate, HSV->RGB; or even taking scotopic vision into account) And: Usually telescopic observers switch to night mode (red-only)... :-)