Calcium II H line and K-line Filters

DayStar is proud to offer Calcium H ( 3969Å ) and two Calcium K-line (3933.7Å ) filtering systems. Traditionally, university research has employed the Calcium K line for studies of Calcium on the Sun.  These studies have been instrumental in determining depth of the solar atmosphere. Calcium offers TWO strong absorption lines at 393.3nm and at 396.9nm, known as the K and H lines.   Researchers have previously avoided the H line for academic research, as it is very close to the Hydrogen Epsilon line.  For purposes of clarity in isolating Calcium, and because imaging sensors offer similar sensitivity to the K as the H lines of Calcium, the K has to date been the target of choice in Calcium filters.  

However, as the visual spectrum ends at approximately 400nm, the further we venture below this wavelength, the more difficult it is for observers to visually see the image.  The H line for visual observations, is much closer to the visual spectrum and easier to see in high contrast violet color. Some observatories have been imaging in Ca II H line, such as the Dutch Open Telescope with outstanding results.

DayStar Calcium H-line Filter assemblies
5.0Å Single cavity visual series filter system $4600.00
$3910.00 after instant rebate

Suitible for amateur and University settings - for visual
and photographic, indoor or outdoor observing settings.

Image by Dutch Open Telescope 450mm aperture telescope
Observatorio del Roque de los Muchachos • Instituto de Astrofísica de Canarias

DayStar Calcium K-line Quantum Filters

2.0Å Single cavity University series filter system $6,670.00

$5,669.50 after instant rebate
Suitible for academic purposes - Ideal application: with CCD photography or indoor visual viewing environment

DayStar's new Quantum controls on Calcium II K line are perfectly suited for academic studies in mapping the 3-dimensional structure of the Chromosphere. By controlling wing shift of the Ca II K line filter with precision accurate to 0.1Å, studies can depict intensity differences between the K3, K2 and K1 lines. Observation of the complicated structure of subordinate peaks offer views through different levels in the solar atmosphere.
A screen-shot of the new DayStar Quantum Control Software for Calcium II K line. A screen-shot of DayStar Quantum Control Software for Calcium II K line.
Solar Flare in Calcium K Line DayStar Calcium K Line image

DayStar 2.0 Å Calcuim K-line filtergrams taken June 8, 1982
with a 125mm aperture telescope at 3000mm prime focus.

* Note. Calcium H and K-line filters do not require F/30 configurations.  They may be used at F/15 or F/20 or greater.  They also do not use the same RED or Yellow glass Energy Rejection Prefilter.  Rather, we recommend dielectric "hot mirror" UV/IR cut filters introduced prior to focus.  Additionally, we suggest an additional neutral density solar film on apertures above 150mm or for long-term dedicated applications.

* HALF-BANDWIDTH: The term half-bandwidth refers to an optics industry standard of measure.  On a chart depicting the peak where light is transmitted, that peak's width is measured at the point 50% between zero and full transmission. This term is called half-bandwidth.

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Hydrogen Alpha Filters

Current Delivery Times
Click for In-stock items

0-10 days for:
Original Quark
uestar Quark
Combo Quark
Calcium Quark

2-4 weeks for:
Blocker and Trimmers
ION Filters
CaII H line filters
Quantum upgrade:  
Quantum SE Filters
SolaREDi 66 Scopes

3-6 months for:
Quantum PE Filters
Ca II K Line PE Filters
Sodium Line FIlters
SR-127 Telescope
Solar System Filter Wheel

Calcium Application Note:

Colored glass Energy Rejection Filters made of red or yellow glass block all Calcium light at 3933Å and can therefore not be used for viewing Calcium.

DayStar recommends use of IDAS Brand UV/IR filters in rear-mounted configuration on refractors only. The IDAS Brand UV/IR cut filter has been tested to pass 3933Å light, but reflects UV and IR light back out the front of the telescope unfocused. This application is called a "hot mirror". The UV/IR cut filter must be installed before the FIRST SURFACE which encounters concentrated light such as the diagonal or barlow; whichever comes first.   This application cannot be used in SCT application, as the OTA and secondary will gain heat and possibly cause failure of the adhesive of the secondary mirror.

DayStar does not recommend application of Ca II line filters on SCT telescopes.

DayStar does not recommend application of Ca II line filters on refractors or any telescope with corrector lenses mounted farther back in the optical train which might encounter concentrated light.

Concerned APO owners may prefer to use an ED Doublet Achromat for Calcium applications, as color correction is not an issue when observing in monochromatic light such as this.

For questions about Calcium Energy Rejection, please contact

DayStar Filters LLC • 149 Northwest OO Highway • Warrensburg, MO 64093 - USA
Telephone: 866-680--6563 • • FAX: 1-866-791-0448