If there is one thing you learn from the outset about Venus, it is that it is permanently shrouded in a blanket of cloud, coyly revealing nothing but this impenetrable shield. Indeed, it has always struck me as supremely ironic that the planet that makes the brightest show of itself reveals the least detail. Like many others, I have (only sometimes successfully) used yellow filters to discern vague, barely discernable variations in its bland milky haze.
However, human vision has not evolved for any other purpose than to make best use of the Sun’s primary energies, in order not to stumble over a rodent hole whilst walking through primeval savannah. Yet with modern imaging devices that plumb deeply into the ultraviolet part of the spectrum, structure within the planet’s swirling mists can be recorded. This filter isolates this useful band of the spectrum, providing a window between 300nm and 400nm, barring light either side of this from 200nm to 1,500nm.