Astrodon Photometrics Sloan Filters
$212.00 – $550.00
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Standard sizes are 1.25″, 31mm, 50mm round, and 50mm square. The 1.25″ is 27.5 mm of filter glass mounted in a 1.25″ filter cell. The 31mm is 27.5mm of filter glass mounted in a 31mm ring. More information here:
Unlike other Astrodon filters, the Photometric filters (Johnson-Cousins and Sloan) do not come as 36mm of unmounted glass. For those who want 36mm round for use in a 36mm filter wheel, 27.5 mm of filter glass can be mounted in our 36mm adapter. More information on 36mm mount here:
We also have a limited quantity of 12mm and 25mm (call for pricing and availability). All Astrodon Photometric filters are 100%-Coated for long-term durability and consistency of research with the highest throughput.
NOTE: In Astrodon part numbers we pronounce the ‘ character (apostrophe) as “prime” and the _ character (underscore) we pronounce as “sub.” So u’2_27R should be read as “u prime 2 sub 27 R.”
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- What's in the box?
- Photometrics Sloan Filter Wavelength Graphs
- Photometrics Sloan Filter 50% Points Chart
- Sloan Details
- Detailed Specifications
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 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
Photometrics Sloan Filter 50% Points Chart
- 50% transmission points provided above (+/- 3nm typical)
- Peak transmission guaranteed > 95% (>90% for u’)
- <=0.03%Tabs out-of-band 300 – 1100 nm
- Single striae-free fused silica substrates
- 1/4-wave propagated wavefront prior to coating
- <0.5 arcminute substrate parallelism
- 3.000 +/-0.025 mm substrate thickness prior to coating
- 1.25″ mounted, 49.7 mm diameter and square unmounted standard sizes
- Other sizes up to 150 mm square on a custom basis (see below)
- Proud supplier to Las Cumbres Observatory Global Telescopes, AAVSO, Caltech/Palomar, MIT, Harvard, MacDonald Observatory, and other research organizations and universities worldwide
- Proudly made in the U.S.A.
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.