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Our ERF rejection filters completely block ultraviolet radiation and visible light up to 500n , reducing the light entering the telescope but letting pass especially the red and then the important H-alpha line. These filters are suitable for use with telescopes focal ratio of at least f/25. This configuration is easily archieved using a Barlow lens that is integrated in the Daystar Quark filters. For example, using the Quark filter with the AIRY ED100 (f/6) telescope, this becomes f/25.2. For added security we advise you to insert an IR-cut filter mirror diagonal. In this way also the infrared radiation will be blocked.
Our ERF 100mm filter is equipped with a cell for connection on telescopes with 123mm diameter dew shield. So it's perfect for the AIRY ED100 telescope. The cell is aluminum anodized made with blackened interior, it has an internal velvet to avoid damaging the telescope dew shield and is designed to allow the filter to expand without resistance (when the telescope is pointed at the Sun, the filter is heated and, being free to expand, the image contrast does not reduce).
The cell is designed to allow you to close the filter with the original AIRY ED100 telescope front cap (for added security). More it features three nylon screws (set at 120°) that allow you to set the cell on the telescope dew shield without avoid damaging it.
WARNING: the ERF filters are designed for the use together with Daystar Quark solar filters. Do not use ERF filters to point, observe and photograph the Sun without the Daystar Quark filter. In order to point, observe and photograph the Sun, you have to use both the ERF and the Quark filters.