For telescopes of less than 120mm aperture, Daystar suggest using an ultraviolet and infrared cut-off filter (not supplied) screwed on in front of the diagonal, which reflects these invisible wavelengths back up the telescope to prevent the focal area from getting too hot. The Quark is said to be compatible with f/4 to f/9 refractors. The specially optimised Barlow, which gives an amplification of 4.2 times and contains its own blocking filter, is built-in and cannot be substituted for another one as it has special coatings and Daystar have given it a unique thread. It has a smart anodised black and red aluminium housing, with both two-inch and 1.25-inch barrels, and a brass compression fitting for the eyepiece.

Importantly, it is set at a price point well below other Daystar filters, and below all but the smallest (40mm aperture and under) dedicated hydrogen-alpha telescopes. It comes with a power supply for the heater and has a knob that adjusts the temperature to alter the tuning of the pass frequency. The new Daystar Quark вЂeyepieceвЂ™ is actually not an eyepiece at all, but a new manifestation of this eye-end filter idea: a cylindrical unit the size of a large two-inch eyepiece that fits in the draw-tube or diagonal of your existing refractor, and takes a 1.25-inch eyepiece or a camera nosepiece. The best of these eye-end hydrogen-alpha filters also use a heating element to raise the filter to a precisely-regulated temperature at which it is optimally вЂon bandвЂ™ to reveal the chromospheric surface details. In contrast to the type of filter that goes at the objective end, or is fixed inside, this design necessitates adding a Barlow lens first to make the light from the objective sufficiently parallel for the filtration to work.

For many years they have been producing, amongst other products, high-grade hydrogen-alpha filters that fit to the eye end of a telescope. American company Daystar has a respected name in the solar telescope field.

Daystar quark