Lunt - Calcium Module with B1800 Blocking Filter in Star Diagonal with T2 Connection

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Primarily on imaging systems due to the difficulty of many to visually see in CaK. To be used on telescopes with
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Lunt Solar Systems

Product Description

Lunt Solar -  18mm Blocking Filter 2 " - in Star diagonal with T2 connection     


 THE OBJECT: block unwanted light and pass the solar Calcium K emission line.                

Calcium K (Ca-K) Telescopes and Filters are used to study the wavelength of 393.4nm. This emission line is one of 2 that are produced by Calcium just at the edge of the visible spectrum in a layer that is slightly lower and cooler than the layer viewed in Hydrogen-alpha.Though its pair of spectral lines, H and K, are stronger than hydrogen's visible-light spectral lines, calcium makes up only 0.008 percent of the sun's mass, compared with hydrogen's 90 percent. 
The K line is from calcium ions (ions missing one electron each) that emit and absorb energy in the ultraviolet portion of the solar spectrum in a broad region centered at 393.3 nm (3933 Å). Using a CaK filter shows the outline of Supergranulation cells on the disk of the sun. These massive cells carry hot gas up to the surface, sideways, and back down again.  The fluid motion of this action concentrates the magnetic fields lines at the outer edge of the cells. This concentration heats the surrounding gasses and produce “The Chromospheric Network” of bright calcium emissions. 
Supergranules are around 20,000 miles across, 6000 miles thick and last up to 2 days. About 2500 supergranules cover the solar disk. 
Sunspots extend from the Photosphere into the Chromosphere. Hot gas from the Photosphere also penetrates the Chromosphere in and around active regions producing bright areas called “Plages”. The emission line displays areas of Super Granulation Cells that are brightest and strongest in areas of high magnetic fields such as sunspot activity and active regions. Having the ability to study the Calcium K and the Hydrogen-alpha line provides important insights into the structure, strength, and depth of these active regions.
The Calcium K line is centered at 393.4nm. This wavelength is considered to be slightly outside the visible spectrum on the UV side. While most people can visually see the violet color of the wavelength, many cannot resolve the contrast due to yellowing of the cornea. People who have had cataract surgery are often able to see considerable detail. But, it is for these reasons that the Ca-K line is typically studied via the use of cameras which are able to provide stunning details.
Internal narrowband filters allow for a <2.4 Angstrom bandpass. Primarily an imaging system due to the difficulty of many to visually see everything that CaK has to offer.




Name Lunt - Calcium Module with B1800 Blocking Filter in Star Diagonal with T2 Connection
Manufacturer Lunt Solar Systems


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This Lunt Calcium-K B1800 works great for imaging, although I have also successfully used it visually as well as I am one of the lucky ones that can still see Calcium-K with my 50+ year old eyes. The camera is much more sensitive to Calcium detail than the human eye, as with any Calcium-K filter, so it is mainly for imaging purposes. Although I could have gotten the smaller B1200 or even B600 as the scope I am using only has a 560mm focal length, I opted for the larger B1800 with its larger 18mm aperture to get that extra wiggle room with no chance of vignetting. I also opted for the diagonal version as I prefer an integrated solution for convenience as well as performance. Lunt's built in star diagonal is top notch and is worth it for the modest difference in cost. (Posted on 4/29/2017)
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