Astrodon

INTRODUCING GENERATION 2 IMPROVED FILTERS

(Available June 20, 2012)

The Sloan Digital Sky Survey (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] skyline at 557.7 nm occurs between the g' and r' filters, and is thus 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. 

NEW!  Astrodon introduces Generation 2 Sloan filters based upon ongoing input from research organizations.  The changes include:

1. Better out-of-band blocking from Tave<=0.1% to Tabs<=0.03%. This is espeically significant for the u' filter
2. Different 50%T points for the r' and i'
3. Introducing the z_s filter (826/920nm) with a long wavelength cutoff
4. Introducing the Y fllter (950/1058nm)
5. An improved z' filter  (>820nm) will still be offered
6. All filters come edge-blackened to reduce stray light reflections 

The following is a summary of the 50% transmission points of a variety of SDSS filters from the Large Filter Consortium. The original Astrodon Photometrics Sloan set and the new Generation 2 set are included for comparison.

The Astrodon Photometrics Sloan filters use only dielectric coatings to achieve steep cut-on and cut-offs and peak transmissions in excess of 95%.  

The following is a spectral compilation of actual scans of the Astrodon Photometrics Sloan Generation 2 filter set.

 These filters are parfocal with all Astrodon LRGB and narrowband filters.

Specifications:

• 50% transmission points provided above (+/- 3nm typical)
• Peak transmission guaranteed > 95%  (>90% for u')
• <=0.03%Tabs out-of-band 300 - 1100 nm
• Striae-free, single fused silica substrates
• 1/4-wave propagated wavefront prior to coating
• <0.5 arcminute substrate parallelism
• 3.000 +/-0.025 mm substrate thickness
• 1.25" mounted
• 49.7 mm dia. unmounted
• 49.7 x 49.7 mm square unmounted
• Other sizes up to 145 mm square on a custom basis (see below)
• Proud supplier to Las Cumbres Observatory Global Telescopes, AAVSO and research organizations and universities worldwide
• Proudly made in the U.S.A.

(Click Image to enlarge)

We are now offering close-outs of Gen 1 Sloan filters at significantly discounted prices while quantities last.  See "Close-Outs".