Daystar Filters Energy Rejection Filters 100/120 mm

Daystar Filters Energy Rejection Filters 100/120 mm

Description

Daystar Energy Rejection Filters (ERF) are engineered to reduce the amount of heat entering the optical system during solar observation. They absorb or reflect ultraviolet and infrared radiation while allowing only the useful visible wavelengths to pass. Depending on the model, the ERF may be made from red or yellow optical glass, or from dielectric-coated glass specifically designed to block IR and UV radiation.

The ERF also serves as an aperture mask, ensuring that incoming light reaches the filter at an optimal angle of incidence. Daystar filter assemblies perform best at f/30 or slower, and the ERF helps achieve this focal ratio either by reducing the effective aperture or when paired with a suitable Barlow lens.

To compute the appropriate aperture reduction, the telescope focal length is divided by 30. When a Barlow lens is used, its multiplication factor must be applied before calculation. The 100/120 mm model features a 100 mm ERF glass mounted in a front cell designed to fit refractor tubes with an external diameter of up to 120 mm.

It provides reliable thermal reduction, improved optical stability and safe, long-duration solar observing. Compatible with many refractors, it is an essential component for stable, narrowband solar configurations using Daystar filters.

Technical specifications

• UV/IR thermal load reduction

• Visible-spectrum transmission

• Red, yellow, or dielectric-coated glass depending on model

• 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 compatible with tubes up to 120 mm OD

• Suitable for many refractors

• Optimized for Daystar systems

• Enhanced thermal and optical stability

• Suitable for H-alpha depending on the filter used