Filter—Baader Venus II Ultraviolet Pass
Graphs are in nanometers. Visible light is approximately 390 - 650 nm (the human eye can see very weakly into the 700-800nm range). Graphs used by permission of Coastal Optical System.
A great source for filters at competitive prices is B&H Photo. Get filters at B&H Photo.
This is the most effective ultraviolet-pass filter on the market, sold by Alpine Astro in the US. It utilizes an incredible 20-layer coating!
Of key importance is the critical strong suppression of infrared, though there is a small blip near 1150nm. Of course, it also cuts off all visible light as well.
A step-down ring is necessary to use it with the Coastal Optics 60/4 UV-VIS-IR APO Macro.