Daystar Filters Energy Rejection Filters 100/140 mm

Daystar Filters Energy Rejection Filters 100/140 mm

Description

Daystar Energy Rejection Filters (ERF) are designed to significantly decrease the amount of heat entering the optical system during solar observation. They absorb or reflect ultraviolet and infrared radiation, allowing only the useful portion of the visible spectrum to pass through. Depending on the version, the ERF may be made of colored optical glass or dielectric-coated glass for efficient UV and IR blocking.

In addition to thermal protection, ERFs act as aperture masks to ensure proper angle of incidence for Daystar filters, which operate best at f/30 or slower. This focal ratio can be achieved by reducing the effective aperture or by using a suitable Barlow lens.

The required reduced aperture can be calculated by dividing the telescope focal length by 30. When a Barlow lens is used, the adjusted focal length must be considered. The 100/140 mm model includes a 100 mm ERF glass mounted in a front cell compatible with refractor tubes up to 140 mm in outside diameter.

This ERF provides stable thermal protection, improved optical constancy during extended solar sessions, and optimal performance with Daystar narrowband solar filters. It is a key accessory for safe and efficient solar observation across many refractor configurations.

Technical specifications

• UV/IR thermal reduction

• Visible spectrum transmission

• Colored or dielectric-coated glass

• Aperture mask functionality

• Recommended focal ratio: f/30 or slower

• Compatible with Barlow lenses

• Aperture calculation: focal length ÷ 30

• ERF glass diameter: 100 mm

• Mounting cell fits tubes up to 140 mm OD

• Suitable for many refractors

• Optimized for Daystar filters

• Enhanced thermal and optical stability

• H-alpha compatible depending on filter used