Baader's new 2" LRGBC anti-reflection filters deliver improved colour separation and image quality, this premium set comprises the RGB, Luminance and IR/UV cutoff filters, ideal for serious astro imagers with mono cameras. The high optical quality of the Baader narrowband filters guarantees no loss in sharpness or contrast. Each glass substrate is fine-optically polished plane parallel to deliver a smooth and accurate 1/4 wavefront over the entire surface. Each filter is blocked and polished individually, a special custom polishing operation that sets Baader filters apart from the lower optical quality provided by standard commercially precision polished filter substrates used by most other filter manufacturers.
Coatings are professionally applied in Germany by the most sophisticated equipment available today, ensuring high consistency for bandpass cutoffs, transmission, and out of band blocking. The anti-reflection coatings are evenly balanced on both sides of the filters to reduce surface stresses and prevent deformation of the substrates. The ultra-hard ionbeam deposition ensures the coatings will never degrade from use or normal cleaning. Unlike many competing filters Baader coats each filter individually. Though more costly, this process avoids the coating failures that can result when filters are mass produced.
Through an extensive coating stack design and testing program, Baader has partnered with the world's leading thin film coating company to produce the unique transmission curves. Their ultra steep cutoffs and high transmission (>95%) allowed Baader to do something to a degree no other RGB filter set can manage - they are able to effectively separate the important H-Beta and O-III lines. The Baader Blue filter passes virtually all of the H-Beta and O-III lines, while the Green filter is able to capture all of the O-III line, without encroaching into the H-Beta line. None of the light is wasted by either filter so the O-III is represented as it should be, a teal (blue-green) colour, and H-Beta is captured solely in the blue. Never before has this degree of separation been achieved, and with such high transmission of both lines.
In addition, the Green and Red filter passbands nearly touch, leaving only a sharp notch to block out the primary Mercury/Sodium light pollution line at 580nm. The high transmission everywhere else delivers the shortest combined exposures possible.
In addition to their special transmission properties, the Baader coatings were developed with another key goal in mind to eliminate reflections. To achieve this freedom from reflections required careful balancing of the coating stacks and further extensive testing.
Contrary to former RGB-designs, with the Baader RGBs the G- and R-filters form a very narrow gap but
do not overlap almost at all, in order to transmit the R-channel in sufficient width to work for Full-Frameand
Interline-Chips with equal effectivity, but to sharply exclude the spectral area around 580 nanometer
which carries the main light polluting emission lines of Mercury and Sodium street lamps. Baader RGBs
will produce a darker sky background.
