Baader Planetarium 1.25" U Filter

New and improved with much narrower bandwidth!

A new generation Venus filter that allows Amateurs to image fine detail on Venus for the first time. The latest coating technologies permit the Baader Venus Filter to transmit from 300nm to 400nm, with a peak transmission of 80% at 350nm. The filter completely blocks the rest of the region from 200nm to 1120nm using a 40 layer dielectric coating stack, on top of a special optically polished UG-11 substrate.

The Baader U-filter is for use with UV sensitive CCD cameras or similar imaging equipment  Visual observations are not possible, since the eye is not sensitive in this spectral region.
Until now, amateur efforts typically relied upon deep violet colored filters, or combinations with simpler interference filters, which do not provide the high transmission and efficient rejection outside the important spectral region from 320nm to 390nm

Freedom from Ghosts and Halos:  Baader Planetarium's filters have always been halo and ghost free.  Baader balances each dielectric coating stack to avoid the ghosts and annoying halos that plague other mfgr's filters.

Stackability:  Unlike most other filters, Baader Planetarium  filters are truly designed to be stacked and combined.  This is possible due to the high optical quality and highly efficient anti-reflection multicoatings.  The ability to combine filters opens up many interesting possibilities, permitting  unique spectral characteristics unachievable with any single filter.

Special Filter Cell:  Baader's special filter cell design offers unique features that enhance their reliability and usability.  Though difficult to produce, the ultra-thin filter cell results in the maximum possible clear aperture, in order to minimize vignetting (1¼" Filter clear aperture is 27mm!, 2" Filter aperture is 45mm).  The special threading has been designed to fit the wide variety of eyepieces and accessories (there is significant variation between the 1¼” filter threading used by eyepiece and accessory manufacturers).  The front 'crown' of the filter incorporates milled notches which make handling and threading the filter a more secure operation in the dark.