Antlia U-Venus Filter - 1.25"

Venus's cloud details primarily reflect in ultraviolet (UV) light, which cannot normally be imaged using broadband filters. The Antlia U-Venus filter isolates the critical UV bandwidths and blocks the contrast damaging frequencies beyond 400nm that typically swamp the UV cloud details on camera sensors.

The filter is designed for imaging with astronomy cameras on a telescope. If you use a color planetary camera, remove any protective UV-IR window in front of it, because that window may attenuate the ultraviolet band that contains the cloud details. The sensitivity of most sensors also decreases rapidly at shorter UV wavelengths, so a camera with good UV response helps.

No, this filter is for imaging only. The human eye is insensitive to the ultraviolet wavelengths that this filter transmits, so you will not see anything through it. This filter is not to be used for visual observation, specifically of the Sun or UV light sources.

Longer exposures are expected. The deeper into the UV band you go, the longer the exposure needed to achieve sufficient signal, and the sensitivity of most sensors decreases rapidly at shorter UV wavelengths. Even with the filter's >80% average transmission, plan to increase exposure time or gain.

To use the Antlia U-Venus filter for UV photography of flowers with a DSLR, the camera must be specially modified to remove the infrared cut filter inside it. Lighting can also limit UV: electronic flash emits less at shorter wavelengths and its glass tube absorbs UV, so expect substantially increased exposure time, UV intensity or ISO sensitivity as the wavelength decreases.

Yes, like any filter placed in the optical path, it will shift the focus point slightly. The filter is 2mm +/-0.05mm thick and is not specified as parfocal, so refocus when adding or removing it or switching filters.