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Astrodon Photometric Sloan Gen2 G Filter - 401/550 nm - 1.25" Threaded Cell - G2-27R

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About Astrodon Gen2 Sloan Filters

Astrodon filters are high performing, durable filters that provide significant aid for astrophotography and research pursuits. Each filter is constructed using a highly innovative process with a single high quality 3 mm thick fused silica substrate and full hard oxide sputtered coatings. Optimally equipped to provide consistency for long-term research undertakings, Astrodon Sloan Photometric filters are fully coated without colored glass. Featuring the highest throughputs on the market, these filters are able to improve signals and enhance faint night sky objects.

Astrodon Gen2 Sloan Photometric Filters - Additional Information

Sloan Digital Sky Survey (SDSS) filters are made to cover the electromagnetic spectrum from 300 nm to the silicon CCD camera sensity limit of approximately 1100 nm. Non-overlapping for the most part, these five filters blend colored glass filters with short-pass dielectric coatings to make the low wavelength side of the bandpass more steep. The 557.7 nm sky glow line appears between the G and R filters and is therefore minimized.

The most common filter system in current use, SDSS photometric filter sets are even used by the Hubble Space Telescope to provide a large reference database for research. This system in conjunction with meter-class telescopes will accomplish much of photometry up to magnitude 23. Upcoming large collaborative survey projects such as the Large Synoptic Survey Telescope - LSST, and Panoramic Survey Telescope and Rapid Response System - Pan-Starrs, will also employ the SDSS filter system.

Using technical contributions from Las Cumbres Observatory Global Telescope Network (LCOGT) among others, Astrodon has taken their Photometric Sloan Filters to the next level. With these Generation 2 Filters, more separation is included between the "G" and "R" filters for greater avoidance of atmospheric skyglow. Unlike the Astrodon "Z" filter, a mere cut-on or long-pass filter, the "Y" and "Z-S" filters were added for the specific purpose of assuring that the high wavelength cut-off is controlled by the filter and not the detector. Finally, leakage already at a minimum is further reduced by tightened out-of-band blocking form average to absolute specification.

Astrodon Gen2 Sloan Filter Highlights

  • Provides 50% transmission points (+/- 3 nm typical)
  • Maximum transmission assured over 95%
  • At most 0.03% tabs out-of-band from 300 nm to 1100 nm
  • Single striae-free fused silica substrate
  • 1/4-wave propagated wavefront prior to coating
  • <0.5 arcminute substrate parallelism
  • Substrate thickness is 3 mm +/- 0.025 mm before coating
  • Proudly manufactured in the USA

Astrodon 1.25" Gen2 Sloan G Filter

Transmitting light in the 401 nm to 550 nm spectral region, this Astrodon round 1.25" threaded cell Sloan Generation 2 "G" Filter has been constructed through a process that includes only a single high quality fused silica substrate 3 mm in thickness and no colored glass. Sloan filters boast the highest possible throughputs. 100% coatings facilitate the necessary durability and consistency for long-term research projects.

Astrodon Sloan Gen2 Filter Detailed Specifications

  • 3 mm +/- 0.025 mm fused silica substrate
  • 25.4 mm +/- 0.1 mm diameter filter size
  • Central 23.4 mm diameter minimum clear aperture
  • TWF: <= 1/4 lambda per any 25mm square area before coating
  • Coating to edge of part
  • AOI: 0º
  • Scratches: <= 0.06mm width; no limit on length
  • Particles/Bubbles: <= 0.4 mm diameter
  • Pinholes/Voids: <= 0.2 mm diameter
  • Edge finish as fabricated
  • Chips: <= 0.5 mm
  • Edge Treatment: Edge-blackened with Enthone M-0-N black epoxy ink
  • Thickness: <= 0.1 mm which may extend 0.5 mm onto top and bottom surfaces