Energy Rejection Filters (ERF) are used on the side of the lens. They reduce the heat in your sunscreen.
Energy Rejection Filters (ERF) will always be used in combination with the Quark series hydrogen and sodium filters when the refractor aperture is greater than 80mm, together with the daystar UV/IR filter (item 63518). and with the combo quark series hydrogen filters whenever working with retro-reflectors or reflectors.
If the aperture of the refractor is LESS than 80mm, the energy rejection filter (ERF) is NOT necessary as long as you do NOT use a mount with tracking and are short sessions, while the UV/IR filter (item 63518) is always necessary. in refractors and must be the first optical element threaded to the diagonal.
The yellow and red energy rejection filters (ERF) CANNOT be combined with the CALCIUM and MAGNESIUM filters of the Daystar QUARK series because the ERF blocks those wavelengths, therefore those two filters if we do not have a compatible ERF filter They will ONLY be used with refractors with a maximum opening of 80mm and always in combination with the UV/IR filter (article 63518) in short sessions and without monitoring.
In addition, the CALCIUM filter of the Quark series does NOT have an internal barlow and its working focal length is between F7 and F30, so a 2x, 3x, 4x or 5x barlow can be used if necessary, before the filter and after the diagonal.
The energy rejection filters (ERF) must be used in retro-reflectors in combination only with the Combo Quark series hydrogen filter since the Combo Quark series does not mount an internal barlow
The difference between the Quark series and the Quark combo is that the first mounts an internal 4.2X barlow and allows you to obtain, with refractors, the ideal working focal lengths of both devices that are between f15 and F30. And that the COMBO QUARK series, by not mounting a barlow, allows its use in f15 retro-reflectors or cassegrains and the like, using a 2x or 3x barlow if necessary, except for the Calcium Quark, which does not have either.
The ideal native focal length for refractors using Daystar's Quark filters is F4 to F8
With a native focal length of 450mm, the quark filter will allow us to see the entire solar disk