What is the Daystar Quark? Functionally it is a very narrowband filter that passes only a tiny amount of color around the hydrogen alpha emission line at 656.3nm (which is deep red). The half value of width is about 0.04nm for the Quark chromosphere version and about 0.07nm for the Quark prominences version. Observing the Sun with such filtering reveals an extraordinary level of details related to the features built of hydrogen – that is most of the Sun’s features.
Technically speaking the Quark filter contains several elements:
- energy rejection filter that rejects excessive radiation, so the filter will not be burnt or overheated
- 4.2x telecentric barlow lens
- etalon interference filter built with mineral mica crystals and regulated by the heated chamber pressure, so the filter centre-line can be adjusted in the range +- 0.05nm.
Daystar Quark filters can be used in combination with any refractor f/4 to f/9. For the telescopes with an aperture larger than 80mm it is recommended to use an additional energy rejection filter – this can be a UV/IR cut filter or a full aperture red or yellow ERF filter – see the Quark manual for details.
Quark chromosphere arrived to me from Dariusz Wiosna – many thanks for sharing the filter for tests! It was attached to the back of TS Photoline 130/910 triplet using about 80mm of extenders. A 2″ UV/IR cut filter was used as an energy rejection filter. At the other end of the Quark, the camera was attached – ASI183MM Pro. This camera pixel size is 2.4um, and it gives a craze pixel scale of 0.13″/px – definitely too much for a 130mm aperture telescope. To reduce the recorded file size I used pixel binning x3, and it helped a lot. However, the binning in CMOS cameras is being done in the driver, so the transfer from the camera to the computer is done at full resolution. That’s why for the full ASI183 frame and 16-bit pixel depth the framerate was modest 10fps.
Quark chromosphere is designed to observe the Sun chromosphere (no surprise here), which is a 2000km thick layer of solar atmosphere located just above the photosphere. In the chromosphere, the temperature rises from about 5,700 to 20,000K and it is hot enough to excite hydrogen to emit the deep red light. Quark chromosphere filter allows also to observe prominences, but the exposure time needs to be extended to capture these features.
There are many distinct features visible at the Sun in the hydrogen alpha band – my favorites are flares and prominences. Solar flare is a relatively intense, localized emission of electromagnetic radiation. Flares are often accompanied by coronal mass ejections and other eruptions. Flares are very dynamic objects with a duration of approximately tens of seconds to several hours, with a median duration of approximately several minutes. In the image below you can see how quickly details in the flares around 3712 sunspot groups changed. These three images were captured every two minutes only, and the actual distance between these two large sunspots is about 90,000km.
Prominences are large plasma and magnetic structures extending outwards from the Solar surface. Prominences are anchored to the Sun’s surface and extend into the solar corona. They can last up to several weeks looping hundreds of thousands of kilometres into space. Since prominences can last for many days it means they get carried across the face of the Sun as it rotates. Prominences seen against the bright solar disk are called filaments.
When the Sun reaches its maximum activity during the 11-year cycle the number and variety of the features visible in the Sun’s face are very large. We also have things called plages, spicules, supergranules, and Ellerman bombs. Using Quark filter visually when the Sun is active you actually cannot be bored. Every time you get back to the eyepiece or to the monitor the items you observed probably changed, and some new things may actually appear.
The number of observed details depends of course on the telescope size. With a modes 70-80mm diameter telescope, only the largest targets can be studied. But when we observe the Sun with a large 120 or more mm diameter refractor, then a great number of objects will be revealed. Big telescope observations of course have their weaknesses as well – you cannot observe the whole Sun’s disk at a time – you may only focus on a specific area that you choose. The same is true for imaging – to capture the whole Sun with a large telescope many single shots must be done and then later merged into a mosaic.
Like the one below – it contains 16 panels. Unfortunately, the panels in polar regions of the Sun were captured in a very poor quality, so they could not be merged into the full picture. Each panel of the Sun in the image below is a final picture made with the following process:
- capture the 1000 frames movie of the selected area with ASI183MM full resolution binned x3 ant 16-bit depth to capture both the Sun surface and prominences
- stack the movie with AutoStakkert into a single picture using the 10% best frames
- merge these pictures into a single image
- reveal details using wavelet sharpening
- do some final processing in Photoshop
The Earth images are included in the photos in this entry just for comparison. Once we have that reference point we can try to imagine how big are the activities that take place in the Sun.
Clear skies!