Available in the U.S. through Alpine Astronomical
P.O. Box 1154, Eagle, ID 83616208-939-2141; www.alpineastro.com
Baader Planetarium unveils its newest series of narrowband imaging filters specifically designed for fast astrographs. Because light passing through narrowband filters at steep angles causes a filter's passband to shift lower in the spectrum, beyond the range where fluorescing gases are isolated, narrowband imaging often produces reduced-contrast images and other problems when photographing with ultra-fast imaging systems. The Baader f/2 Highspeed Filter series combats this problem by shifting the passband of each Hα, O III, and S II filter lower to accommodate the steep light cone of telescopes with extremely fast f/ ratios between f/1.8 and f/3.5. Both air-to-glass surfaces are polished to ¼-wave accuracy and are fully sealed along the edges to protect from moisture damage. Each filter is available in mounted 1¼- or 2-inch low-profile threaded cells designed to fit in any standard filter wheel. See the distributor's website for pricing and availability.
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