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Astrodon Sloan Gen2 z' Filter

SKU DON-z’2_27R
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Original price $349.00 - Original price $905.00
Original price
$349.00 - $905.00
Current price $349.00
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More information

  • 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.

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.




3.0mm +/-0.025mm fused silica

Filter Size

25.4mm +/-0.1mm diameter

Clear Aperture

Central 23.4mm diameter minimum


= 1/4 lambda per any 25mm square area before coating


=0.5 arcminute before coating


To edge of part


0 degree


= 0.06mm width; no limit on length


= 0.4mm dia.


= 0.2mm dia.

Edge Finish

As fabricated



Edge Treatment

Edges blackened with Enthone M-0-N black epoxy ink.


= 0.1mm. It may extend 0.5mm onto top and bottom surfaces.

In the Box

Photometric Sloan Filter