Optolong Ultra High Contrast (UHC) Filter

Warning: DO NOT ATTEMPT SOLAR OBSERVATION WITH THIS FILTER. DIRECTLY OBSERVING THE SUN THROUGH THESE FILTERS CAN RESULT IN IRREVERSIBLE BLINDNESS.

Introducing the Optolong UHC (Ultra High Contrast) Filter:

The Optolong UHC Filter with a narrower passband is specifically engineered to deliver superior contrast in observing and capturing various deep-sky objects, making it an ideal choice for urban environments plagued by severe light pollution.

Description: The UHC (Ultra High Contrast) broadband filter is meticulously designed to enhance the visibility of celestial objects in the night sky. It achieves this by selectively reducing the transmission of wavelengths of light pollutants, notably those emanating from artificial light sources like mercury vapor lamps, high and low-pressure sodium vapor lights, and the undesirable natural light caused by neutral oxygen emission in our atmosphere, commonly referred to as "skyglow." In addition to this light-pollution mitigation, the filter exhibits high transparency in the primary emission lines of nebulae, including OIII (496nm and 500nm), H-beta (486nm), NII (654nm and 658nm), H-alpha (656nm), and SII (672nm). Consequently, it is well-suited for improving contrast and detail when observing or photographing celestial objects in suburban areas plagued by heavy light pollution.

Main Use and Performance:

• Suitable for use with color CCD cameras and unmodified DSLRs.
• The UHC filter, with its narrower passband, provides significantly higher contrast compared to the CLS filter. Hence, it is particularly effective in urban environments with substantial light pollution.
• Notably, the UHC filter offers exceptional views of celestial objects like the Orion Nebula (M42).
• It's important to note that light pollution filters do not eliminate the effects of light pollution or increase the brightness of celestial objects. Instead, they enhance the contrast between nebulae and the night sky, accentuating the nebulae's visibility.

Technical Data:

• Substrate: Optical glass
• Average Transmission (Tave): >95%
• Blocking Range: 300-700nm
• Blocking Depth: OD3, effectively blocking light pollution lines by over 99%
• Surface Quality: 60/40 (Compliant with MIL-O-13830A, MIL-C-48497A standards)
• Transmitted Wavefront RMS: ¼ λ
• Parallelism: 30 seconds

Coating Technology: The Optolong UHC Filter employs advanced coating technologies to enhance durability and optical performance:

• Multi-layer Anti-Reflection Coating: This minimizes reflections and maximizes light transmission.
• Non-Cementing Optical Substrate Coating: Enhances scratch resistance.
• The filter utilizes Ion-Assisted Deposition Coating Technology for precise and stable performance, ensuring that the filter's central wavelength (CWL) remains consistent despite temperature fluctuations.
• A planetary rotation system is employed during the coating process, guaranteeing uniform and precise coatings. This results in high transmission in the pass-band and superior optical density in the off-band.

Packaging: The filter is thoughtfully packaged for protection:

• Outer Box: Silver box
• Plastic Box: Made of PP material
• Lining: Features imported high-pressure white EVA material.

In summary, the Optolong UHC Filter is a valuable tool for astronomers and astrophotographers, tailored to enhance celestial observations in light-polluted urban areas. Safety warnings must be adhered to diligently, particularly regarding solar observations, to prevent potential eye damage.

Interpreting the Chart: The provided chart offers insights into the filter's performance characteristics:

• The horizontal axis represents the wavelength in nanometers (nm).
• The vertical axis illustrates transmission percentages (%).
• The RED line corresponds to the H-alpha line, while the GREEN line represents the emission of OIII. Artificial emission lines are depicted in ORANGE.