ERF pre-filter E-110N75 for H-alpha solar monitoring | DayStar

Anyone who wants to view the Sun in H-alpha must first keep the heat of the sunlight outside the telescope. The DayStar ERF E-110N75 is an energy rejection filter that you place in front of the opening of your telescope to achieve this.

The filter blocks most of the ultraviolet and infrared light and lets through mostly red light. This means that much less heat gets into the telescope and the H-alpha filter at the back, like a DayStar Quark, is protected. For prefilters and H-alpha filters, you can find them together in our sunwatch filters.

Check beforehand whether the size of the aperture matches the outer diameter of your tube or dew cap. If you are unsure, please contact us. Never look directly at the sun through an ERF: the filter is only safe when used as part of a complete H-alpha setup, as intended. Read ahead our guide on sunscreens.

There are more sizes, such as the ERF E-120N80.