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Lunt B1800 Calcium K Blocking Filter
Lunt B1800 Calcium K Blocking Filter
Lunt B1800 Calcium K Blocking Filter
Lunt B1800 Calcium K Blocking Filter
Lunt B1800 Calcium K Blocking Filter

Lunt B1800 Calcium K Blocking Filter

by Lunt Solar Systems
SKU LSS-LS18CaKMDd
CA$2,373.00 - CA$2,373.00
CA$2,373.00
CA$2,373.00 - CA$2,373.00
CA$2,373.00
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  • Isolates the 393.4 nm Calcium K emission line
  • Bandpass of less than 2.4 Angstroms for high-contrast views
  • 18mm clear aperture blocking filter
  • Fits standard 2-inch focusers with T2 camera threads
  • Converts a standard nighttime refractor for solar imaging
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  • Description
  • FAQ
  • Specifications
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  • Lunt B1800 Calcium K Blocking Filter

    The Lunt B1800 Calcium K Blocking Filter isolates the 393.4 nm emission line with a narrow sub-2.4 Angstrom bandpass, revealing a dynamic layer of the Sun's chromosphere often missed by other filters. This 18mm blocking filter module is designed as a dedicated imaging system, fitting into a standard 2-inch focuser to convert your nighttime refractor into a specialized solar instrument for studying solar magnetism.

    The Calcium K Line: Imaging Solar Magnetism at 393.4 nm

    This filter is precisely centered on the Calcium K (Ca-K) line at 393.4 nm, a wavelength produced by calcium ions just at the violet edge of the visible spectrum. This emission reveals a layer of the chromosphere that is slightly lower and cooler than what is seen in Hydrogen-alpha, providing a complementary view of solar activity. Ca-K imaging excels at showing super granulation cells and is particularly sensitive to areas of high magnetic fields, making sunspots and surrounding active regions appear with dramatic brightness and structure.

    A Sub-2.4 Angstrom Bandpass for High-Contrast Chromosphere Imaging

    To isolate the faint details within the Ca-K line, the Lunt B1800 employs an internal narrowband filter with a bandpass of less than 2.4 Angstroms. This tight specification is critical for rejecting overwhelming continuum light from the photosphere, allowing the faint chromospheric network and plage to stand out with sharp contrast. The result is a dark, clean background against which the brightest, most magnetically active solar features are rendered in stunning detail by your camera.

    Optimized for 393.4 nm Imaging: Why Ca-K Favors the Camera Sensor

    The 393.4 nm Ca-K wavelength is notoriously difficult for the human eye to perceive with high contrast. As we age, the cornea naturally yellows, filtering out the deep violet light where Ca-K resides. For this reason, the B1800 is primarily an imaging system, as modern camera sensors are highly sensitive to this wavelength and can capture incredible detail that is visually inaccessible to most observers. While some individuals, particularly those who have had cataract surgery, may see more detail, the most rewarding results from this filter will come from photography.

    Flexible Integration: 2-inch and T2 Connections for Standard Refractors

    Designed for versatility, the Lunt B1800 Ca-K module can convert most standard nighttime refractors into a capable Ca-K solar telescope. It is available in housings that slide into any 2-inch focuser and provide industry-standard T2 (M42x0.75) threads for direct, secure attachment of most astronomy cameras. This ensures a solid imaging train, whether you choose the straight-through or star diagonal configuration, allowing you to focus on capturing the dynamic solar surface.

  • Can I use the Lunt B1800 Ca-K filter for visual observing?

    The Lunt B1800 Ca-K filter is designed primarily as an imaging system. The 393.4 nm wavelength is deep in the violet part of the spectrum, where most people have very low visual contrast sensitivity. While you may see a violet disk, the fine details like super granulation are best captured with a camera.

    What kind of telescope do I need for the Lunt B1800 Ca-K filter?

    This filter module is designed to work with most standard nighttime refractor telescopes. It can also be used with Lunt's Modular Telescopes when they are configured for nighttime use. It is not a standalone filter and requires a telescope to function.

    How does the view in Calcium K with the Lunt B1800 differ from Hydrogen-alpha?

    Calcium K shows a lower, cooler layer of the chromosphere than Hydrogen-alpha. While H-alpha is excellent for prominences and surface filaments, Ca-K excels at highlighting areas of strong magnetic fields. This makes sunspots and their surrounding active regions (plage) appear as intensely bright areas, offering a different and complementary perspective on solar activity.

    What specific solar features will the Lunt B1800 Ca-K filter show on an active Sun?

    During periods of high solar activity, the Lunt B1800 Ca-K filter will reveal a wealth of detail. You can expect to image:

    • Bright Plage: The bright, complex regions surrounding sunspot groups.
    • Sunspots: Displayed with high contrast against the surrounding plage.
    • Supergranulation Network: The large-scale convection cell pattern across the solar disk.

    Will the Lunt B1800 Ca-K filter work with my 100mm f/7 refractor for imaging?

    Yes, a 100mm f/7 refractor is an excellent choice for use with the Lunt B1800 Ca-K filter. The 18mm blocking filter provides full-disk illumination for telescopes with focal lengths up to 1800mm, so your 700mm focal length scope is well within the ideal range for capturing the entire Sun in a single frame.

    Why is the Lunt B1800 Ca-K filter's bandpass <2.4 Angstroms?

    The sub-2.4 Angstrom bandpass is essential for achieving high contrast. The Sun's photosphere is incredibly bright, and this light would wash out the faint details of the chromosphere. The narrow bandpass blocks this unwanted light, allowing only the specific 393.4 nm Ca-K wavelength to reach the camera sensor, dramatically improving image contrast.

  • Wavelength 393.4 nm (Calcium K)
    Bandpass <2.4 Angstroms
    Blocking Filter Aperture 18mm
    Housing Options 2" Star Diagonal or 2" Straight-Through Tube
    Camera Connection T2 (M42x0.75) Threads
    Telescope Compatibility Refractor Telescopes
    MPN LS12CaKMD
    GTIN LS6CaKMD
  • Lunt Solar Systems 5-Year Warranty