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Post Info TOPIC: Wratten #11 filter


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Wratten #11 filter
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A Wratten #11 yellow-green filter is similar to a vintage pale green-yellow filter made by Voigtlander, and used for colour correction in photography.
For astronomy, the filter will enhance contrast on the moon, and reveal detail on Mars (darkens the maria), Jupiter (cloud structure/the Great Red Spot) and Saturn (clarifies the Cassini division in Saturn's rings).
The yellow filter has a high transmission rate (78%), allowing only yellow light to pass through, so is ideal for general planetary and double star work even in small scopes (a recommended minimum aperture is 60mm).
The filter will also reduce an achromatic refractor's false colour (violet fringes mostly noticeable on bright or high contrast objects) and give crisper views. This is a semi-usable, and cheaper, alternative to specialist chromatic aberration correcting filters (such as the Baader semi-apo filter).

Contrasts well with the red and blue characteristics of surface features on Jupiter and Saturn. Darkens the maria visible on Mars; and clarifies the Cassini division in Saturn's rings.

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