The Ultraviolet Venus Filter - 1.25-Inch Round Mounted by Baader Planetarium:
Another unique new filter from Baader Planetarium. For the first time, amateurs can now record cloud structures on Venus. The Baader Venus Filter enables amateurs to successfully image in the deep UV, a spectral region normally inaccessible.
The latest coating technologies permit the Baader Venus Ultraviolet Filter to transmit from 300nm to 400nm, with a peak transmission of 80-percent! The filter completely blocks the rest of the region from 200nm to 1500nm, through the use of a complex 20 layer dielectric coating stack, on top of a special UG-11 substrate. Up till 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. Given the poor transmissions of many optics in the UV and the lower sensitivity of some CCDs to this wavelength, high filter efficiency and complete rejection at longer wavelengths becomes paramount to recording good contrast at reasonable exposures. The same high optical quality and features as the other Baader filters ensures the highest contrast and sharpest images possible.
Interestingly, the solar Calcium K-Line is also within the pass band of this filter. This opens up the exciting possibility for recording flare structures on the solar disk or edges. The Baader U Filter has become the choice of UV imagers exploring the UV world of landscape, floral, and even forensic imaging. The latest 1.25-inch filter now has even higher transmission and improved out of band blocking. By using our DSLR-2 filter adapter ring plus the appropriate filter step ring (HDT-Rings), UV imagers can conveniently mount the U-Filter to their camera lens. Please Note: The Baader Venus U filter is only applicable for imaging with Webcam, Digital, and CCD cameras (Visual Observation is impossible, due to the eye's insensitivity to the UV). For successful imaging, we recommend the use of a UV sensitive astronomy CCD camera (ie, SBIG ST-2000XM) and at least a 5" telescope, or a webcam and 8" telescope.
Baader Planetarium Ultraviolet Venus Filter Features:
True Optical Quality: Baader glass substrates are of true optical quality. Most other filters are merely made from raw flame-polished, "optically flat", or sometimes a top quality commercially polished filter glass (fine for camera filters), resulting in wavefront deformations that damage image sharpness and contrast when used with telescopes. Baader Planetarium filters are made from striae-free substrates, and actually fine optically polished flat to within 1/4 wave p-v over the entire surface, plane parallel to within 30 seconds of arc! This important and unique custom step adds cost - but the result is a filter that maintains the full wavefront quality of the telescope without double images or ghosting, even at high magnifications. Critical to maintaining this level of flatness are Baader's carefully balanced coating designs, which prevent coating surface stresses from warping the substrate. Such high flatness enables Baader filters to be used far in front of the focal plane, ahead of star diagonals and digital cameras. They are particularly well suited for attachment to the nosepiece of the Maxbright Binocular Viewer (other manufacturer's filters must be used in pairs, attached to the eyepieces).
Filter Durability:Filter durability has always been a hallmark of Baader Planetarium. The multi-layer dielectric coatings are plasma-assisted and Ion beam-hardened using the latest technology (the coatings are harder than the glass substrate itself!). Baader filters withstand repeated real-world exposure to the elements and physical cleaning. Users need not leave their precious filters dull and dust encrusted to avoid cleaning - Baader filters may be used and cleaned without fear. We have heard sad stories from owners of other simpler soft-coated dielectric filters, who have seen their coatings degrade from normal exposure to moisture, or wiped away from routine cleaning. Some manufacturers even resort to sandwiching their delicate coatings in between two layers of glass (and risking blurred double images as well as eventual degradation from the edges inward). Baader Filters will truly last a lifetime.
Stackability:Unlike 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 multi-coatings. The ability to combine filters opens up many exciting 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 (1.25-inch Filter clear aperture is 27mm, 1.25-inch Filter aperture is 45mm). The special threading has been designed to fit a wide variety of eyepieces and accessories (there is significant variation between the 1.25-inch 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.
Low cost:Despite high quality and advanced technology, Baader Planetarium filters are affordable. By leveraging high volumes across all filters in the Baader family, these filters can be offered at very reasonable prices.
OPT Product Number: BA-FUV-1