Burgess Optical C.A.S.S. (Minus Violet) Filter (Pre-owned)

Burgess Optical C.A.S.S. (Minus Violet) Filter (Pre-owned)

The filter is in great condition with no scratching or dammage to the glass that might affect its use. 

The Burgess Optical C.A.S.S. Minus Violet Filter is a specialized 1.25" astronomical filter designed to reduce unwanted violet and blue-violet chromatic aberration commonly seen when observing through achromatic refractor telescopes. By reducing the effects of out-of-focus violet light, the filter can help produce a cleaner, higher-contrast image, particularly around bright objects such as the Moon and planets. The C.A.S.S. filter is a vintage accessory that is particularly well suited to owners of classic achromatic refractors.

Function: A minus violet filter selectively reduces portions of the shorter-wavelength blue/violet light that an achromatic refractor does not bring to the same focus as longer wavelengths. This can reduce the visible purple or violet halo around bright objects and may provide a more pleasing, higher-contrast view. The exact amount of improvement depends on the telescope and observing target. Astronomy users have historically used minus-violet filters specifically to address false color in achromatic refractors.

• Manufacturer: Burgess Optical
• Model: C.A.S.S. Minus Violet Filter
• Type: Minus Violet / Chromatic Aberration Reduction Filter
• Application: Visual astronomical observing
• Primary Use: Reduction of violet/blue-violet chromatic aberration