The Sloan Digital Sky Survery (SDSS) filters were designed by Fukugita et al. (Ast. J., 411/4, April 1996, p. 1748-1756) to include five mostly non-overlapping filters covering 300 nm to the sensitivity limit of silicon CCD cameras near 1100 nm. They combined colored glass filters and short-pass dielectric coatings to steepen the low wavelength side of the bandpass. The [O I] sky glow line at 557.7 nm occurs between the g’ and r’ filters, and thus is reduced.
The SDSS photometric system is the most common filter set used today. The Hubble Space Telescope is equipped with an SDSS set that provides a large reference database for research. Much of photometry up to magnitude 23 will be done in this system with meter-class telescopes. The upcoming large collaborative survey projects (Large Synoptic Survey Telescope – LSST; Panoramic Survey Telescope and Rapid Response System – Pan-Starrs) will also use SDSS filters.
Astrodon Photometrics Sloan Filters have evolved to our current Generation 2 filters with technical input from Las Cumbres Observatory Global Telescope Network (LCOGT) and others. Additional separation was included between the g’ and r’ filters to better avoid atmospheric sky glow . In particular the Y and z_s near-infrared filters were added to ensure that the filter, and not the detector, controlled the high-wavelength cut-off. This in contrast to our z’ filter, which is simply a cut-on, or long-pass filter. Lastly, out-of-band blocking was tightened from an average to absolute specification to further minimize the already small leakage. A summary of the 50% points is provided in the chart below.
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What’s in the box?
Photometrics Sloan Filter
SLOAN FILTER SPECIFICATIONS
SPECIFICATIONS COMMON TO ALL FILTERS
Substrate: 3.0mm +/-0.025mm fused silica
Filter Size: 25.4mm +/-0.1mm diameter
Clear Aperture: Central 23.4mm diameter minimum
TWF: </= 1/4 lambda per any 25mm square area before coating
Parallelism: </=0.5 arcminute before coating
Coating: To edge of part
AOI: 0 degree
Scratches: </= 0.06mm width; no limit on length
Particles/Bubbles: </= 0.4mm dia.
Pinholes/Voids: </= 0.2mm dia.
Edge Finish: As fabricated
Edge Treatment: Edges blackened with Enthone M-0-N black epoxy ink.
Thickness </= 0.1mm. It may extend 0.5mm onto top and bottom surfaces.