49.7 x 49.7 mm square Unmounted Astrodon Johnson/Cousins UV edge-blackened-UV*_50S-200041 (2nd Quality Discount)

Astrodon SKU: UV*_50S-200041
UVenus-700x559 (6795821023385)

49.7 x 49.7 mm square Unmounted Astrodon Johnson/Cousins UV edge-blackened-UV*_50S-200041 (2nd Quality Discount)

Astrodon SKU: UV*_50S-200041
Regular price $550.00 Sale price $440.00 Save $110
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This individually serialized filter, UV*_50S-200041, has been scored at 9.9 and has a 12.50% discount. Astrodon 2nd Quality filters are still covered by our warranty for longevity, but are otherwise sold “as is” and are not returnable.

Astrodon 2nd Quality Filters are sold at a discount. 2nd Quality Filters are individually evaluated and graded for edge chips, scratches, pinholes and inclusions according to the standards set below:

Edge Chips: Score 1 point for each edge chip. Score 1 additional point for each edge chip that extends into the filter more than 2mm from the edge.

Pin holes: Score 1 point for each pinhole. Score an additional point for each pinhole that is “large”.

Scratches: Score 1/2 point for each scratch.

Inclusions: Score 1/2 point for each inclusion.

Subtract the sum of the points from 100 and divide by 10. This is the filter score.


Astrodon introduces a breakthrough in UV filters for CCD imaging. A durable, hard-coated UV filter of the highest quality having the best transmission available.

  • Image the cloud structure of Venus and Jupiter with CCD cameras on a telescope.

  • Use for general UV photography (flowers, insects, forensics).

The Astrodon-Schuler UV filter has traditionally been used for imaging Venus. It is made from several colored glasses, but only transmits ~ 65% of incoming UV light in the 300 – 400 nm region. Another vendor recently discontinued a 1.25″ mounted UV filter due to NIR light leakage, but offers a 2″ unmounted version that only reaches 80%T. Astrodon offers you both sizes and higher performance. Like the highest quality Generation2 Astrodon LRGB filters, the UVenus filter minimizes halos around bright stars.

Astrodon UVenus filters are guaranteed to achieve >90% transmission. The actual scan below has an average transmittance of 98.2% from 325 – 381 nm, while minimizing out-of-band light leakage. This outstanding performance saves you time when imaging weak UV signals, while providing high contrast due to low light-leakage. You do not need a separate filter to block the NIR with the UVenus filter.


  • 1.25″ mounted and 49.7 mm diameter unmounted

  • 3.000+/-0.025 mm substrate thickness

  • Single, striae-free fused silica substrate

  • 1/4 wave substrate prior to coating

  • < 0.5 arcminute parallelism before coating

  • Hard coated to edge

  • Guaranteed to > 90%T peak transmission (>94% typical)

  • <0.01%T 285-305 nm; <0.1%T 420 – 1100 nm

WARNING! This filter is NOT to be used for visual observations, specifically the sun or UV light sources.

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