Daystar Filters' Sodium QUARK Na D-Line Eyepiece Solar Filter is built to use a traditional nighttime astronomical OTA for solar observation. It departs from traditional K-line tuned filters, and focuses on the 5895.9Å D-line wavelength. This wavelength is very narrow but also very bright, so a specialized filter is required to isolate it. Na D-line is a low excitation line emitted when the low chromosphere is heated, usually at footprints of flux loops passing through a flare, as sodium D line reflects the lower chromosphere it shows impulsive-phase flare eruption kernels. Visual and photographic images will also reveal sunspot detail, plague, and granulation, but are much brighter and more easily visible. This configuration of the QUARK is not suited for off-axis application.
With its integrated 12mm blocking (21mm clear aperture) filter there are no OTA aperture limitations, but Daystar recommends the use of refractor-style scopes with focal ratios between f/4-f/8, and you can enjoy full-disk viewing with focal lengths up to 450mm. Daystar further recommends the use of a UV/IR cut and objective Energy Rejection Filter (ERF) for safety. Built into the system is a 2-element 4.2x Barlow lens to boost the power of any eyepiece used with it, and its telecentric lens configuration ensures consistent image size and magnification across the entire field of view. Additionally, the Barlow lens is fully baffled to absorb scattered light to enhance contrast.
This all-in-one filter design enables the use of nighttime telescopes for solar viewing, and is engineered to eliminate unnecessary components which reduced the size and weight. This streamlined form enables it to accept 1.25" eyepieces, and comes with a 1.25" snout - with an optional 2" snout available for use with larger drawtubes. The filter is powered via a micro-USB port, and Daystar includes a power cord and an AC adapter to meet the high-power requirements of 5 VDC 1.5A. To enable its use at home and abroad, a set of international outlet plugs is provided with adapters for the US, UK, EU, and Australia.