Custom Scientific Filters

Custom Scientific makes filters and other optical components for research and amateur astronomy. Many of the larger filters made by Custom Scientific are one of a kind filters made to the specifications of a particular user. Custom Scientific UVBRI filters are used world wide by researchers in the field of photometry. Both of the LRGBC sets (1.25" and 50mm) we sell from Custom Scientific are designed to SBIG's specifications. The transmission curves are designed to give excellent color balance to continuum light (stars) while at the same time accurately balancing BOTH the dominant H-alpha and OIII emission energy typically found in many nebula.

Custom Scientific 1.25" RGBC 4 filter set:

This RGBC filter set is the standard SBIG set that comes with the CFW8A filter wheel and is intended for use with the ST-7/8/9/10/2000 cameras. The set is also available separately. It is designed to give a proper balance of continuum light from stars and proper ratios of H-alpha and [O-III] emission line sources (e.g., bright nebula and planetary nebula) at the same time. These professional quality, high transmission, dichroic filters have been tested over time by some of the best astroimagers in the world. Many of the remarkable images seen in the gallery of Sky & Telescope and Astronomy magazines have been taken with this filter set and an "ST" series camera. The colored filters are parfocal, antireflection coated and IR blocked. The clear filter is AR coated only. Click here for current prices.

Custom Scientific 50mm LRGBC five filter set

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This LRGBC five filter set for the STL series cameras is designed to drop into the STL filter carousel without vignetting the largest (35mm format) CCD in the series. The STL carousel is threaded for 48mm ("2") filter cells as well, but the full 50 mm diameter of these filters provided the maximum aperture for the large format CCDs. For this reason they are supplied without threaded cells. Like the smaller Custom Scientific RGB filters, this 50 mm filter set is professional quality, antireflection coated, IR blocked. The Luminance filter is UV and IR blocked to match the RGB cutoffs, it is also AR coated. The clear filter is AR coated only. Click here to see the luminance and clear filter transmission characteristics. Click here for current prices.

Custom Scientific 1.25" and 50mm H-alpha Filters

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SBIG offers two versions of H-alpha filter from Custom Scientific, a relatively narrow 4.5 nm filter and a wider 10 nm filter. Both are available in either 1.25" size or 50 mm size. The smaller 1.25" filter fits in the CFW8A or CFW10 filter wheel and is suitable for the ST-7/8/9/10/2000 cameras. The 50mm size fits in the STL carousel and is suitable for any of the large format STL series cameras. The benefit of the narrower 4.5nm filter is greater suppression of sky background and light pollution. Very detailed images of faint H-alpha nebula can be faithfully captured even when imaging in heavily light polluted skies or under the glare of a full moon. The 10nm filter is also very good at suppressing light pollution, but not quite as good as the narrower 4.5nm filter. The 10nm filter is better for darker skies, and it is also less expensive than the 4.5nm filter. Click here to see the 10nm filter transmission characteristics. Click here for current prices.

Custom Scientific 1.25" and 50mm UBVRI Photometric Filters

In the 1950's Harold Johnson (Yerkes and Macdonald Observatories) established three photometric bands, the U, B, and V based on the sensitivity of the photomultiplier tube that he used at the time. Later on he established red and infrared (R and I) bands using a PMT with enhanced red sensitivity. In the mid-1970's, A.W.J. Cousins and John Menzies (South African Astronomical Observatory) used different filters, that when used with a newer, better detector, would reproduce the Johnson bands. Then, in the 1980's CCD detectors were beginning to replace the photomultipliers so a new set of filters was required that, when used with the CCD's would give the same results as the older filters when used with the PMT. Bessell (Mt. Stromlo and Siding Spring Observatories in Australia) did this in 1990 (PASP, 102, 1990, 1181). It is Bessell's filter definitions that are the industry standard today when using CCD's. These professional quality, polished, AR coated, photometric filters are available in both 1.25" and 50mm sizes. Click here to see the individual filter transmission characteristics. Click here for current prices.