Baader Filters D-ERF 75mm energy rejection filter, IR blocking, dielectric coated (15256)

Plano-parallel round discs: These discs are precision-optically polished to lambda/10 on both surfaces. They feature an advanced infrared antireflection coating (dielectric interference coating system with multiple individual layers) that blocks infrared (IR) heat radiation, preventing heat from penetrating the telescope's OTA, even during extended observing sessions.

Key Benefits:

• Prevents Image Degradation: Thermally induced air currents inside the OTA are minimized, ensuring stable and clear image quality.

• Protects H-alpha Filters: Shields expensive H-alpha filters near the focal point from premature aging caused by heat stress.

• Maintains Stable Wavelengths: Keeps the set wavelength constant, avoiding temperature-induced drifts.

• Enhances Contrast: Multi-layer coatings with only 0.2% residual reflection prevent internal reflections that could reduce image contrast for both the Sun's surface and prominences.

High-Quality Manufacturing:
Producing a precisely flat surface while maintaining flatness during coating deposition requires advanced technical expertise. Only stress-free tempered raw glass is selected to ensure a high-quality final product. Improper manufacturing methods or outdated deposition machines can cause glass deformation, rendering the filter ineffective.

These filters are manufactured using modern ion beam coating machines to minimize heat loading on the glass and create an extremely hard, scratch-resistant coating.

Important Notes:

• D-ERF filters are pre-filters designed exclusively for use with SolarSpectrum H-alpha surface filters and prominence setups.

• This filter must always be mounted in front of the telescope where light enters, with proper orientation toward the Sun (marked on the edge of the filter).

• Warning: Observing the Sun's surface in white light without an additional light attenuation filter will cause irreparable eye damage!

Please Note: These are unmounted filters.

Specifications:

• Coating of optical system: Multi-layer dielectric coating

• Frame type: Lens filters