Daystar Filters Energy Rejection Filters 80/120 mm

Daystar Filters Energy Rejection Filters 80/120 mm

Description

Daystar Energy Rejection Filters (ERF) are designed to significantly 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 spectrum to pass. Depending on the model, the ERF may be manufactured from red or yellow glass, or from dielectric-coated glass engineered to block IR and UV efficiently.

The ERF also functions as an aperture mask, ensuring a proper angle of incidence for incoming light. Since Daystar filter assemblies perform best at f/30 or slower, the ERF helps achieve this focal ratio by reducing the effective aperture or by working in combination with a suitable Barlow lens.

To determine the proper reduction aperture, the telescope focal length must be divided by 30. When using a Barlow, the multiplied focal length must be used in the calculation. The 80/120 mm model includes an 80 mm ERF glass mounted in a cell designed to fit refractor tubes with an external diameter of up to 120 mm.

It provides effective thermal reduction, improved optical stability, and safe long-duration solar observing. Compatible with many refractors, it is an essential component for stable and high-performance narrowband solar observation using Daystar systems.

Technical specifications

• UV/IR thermal load reduction

• Visible-spectrum transmission

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

• Aperture mask functionality

• Recommended focal ratio: f/30 or slower

• Compatible with Barlow lenses

• Reduction calculation: focal length ÷ 30

• ERF glass diameter: 80 mm

• Mounting cell compatible with tubes up to 120 mm OD

• Suitable for many refractors

• Optimized for Daystar systems

• Enhanced thermal and optical stability during long solar viewing

• Suitable for H-alpha observation depending on filter used