What are QUARK solar filters?
The American manufacturer DayStar offers solar filters under the name QUARK. These have revolutionised solar observation:
- QUARK filters are relatively inexpensive compared to other filters optimised for a specific spectral line.
- They are easy to use: you do not need an expensive solar telescope or any modifications. Simply use a small refractor and insert the QUARK into the focuser between the diagonal mirrors and an eyepiece. We recommend using an additional UV/IR blocking filter (see "Recommended accessories"). This filter is simply screwed into the eyepiece.
- QUARK filters are equipped with a heater that uses thermal expansion to keep the distance of the filter etalon constant. This ensures that the filter always works properly.
- There are already several models in this series, so you can simply change the filter like an eyepiece and switch between observations in H-alpha, calcium-H or sodium-D light.
Why the sodium D line?
In the sodium D2 line at 589 nanometres, we can see fine details in sunspots, solar flares (plages) and the granulation of the photosphere. Solar flares are also visible in sodium light earlier than in white light.
The image is brighter than with calcium and H-alpha filters, making observation easier and allowing for shorter exposure times in photography.
Please note: This QUARK solar filter is suitable for refractors with an aperture ratio between f/4 and f/8.
