Filter

Astrodon Photometrics Johnson-Cousins Filters

Spectral profiles designed after UV, B, V, Rc, Ic Johnson/Cousins
Improved B filter extending blocking >1100 nm and eliminating small light leaks that affected measurements of reddest stars in our initial filters
100% coated – no colored glass
Peak transmission guaranteed > 90%
<0.01%T(ave) typical out-of-band 300 – 1100 nm; additionally =<0.1% Tabs for B***
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
Parfocal with all Astrodon filters
Edge-blackened
1.25″ mounted
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
Chips: </=0.5mm
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.