Solar Telescopes

Grid List

Set Descending Direction

1-12 of 49

Page:
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5

Grid List

Set Descending Direction

1-12 of 49

Page:
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5

A solar telescope is a refractor-based optical system that uses special filters to view specific wavelengths of light, the most common of which is H-alpha.  The H-alpha telescope allows safe observation of the entire solar disc, providing superb views of prominences, chromosphere, and surface details such as sunspots, plagues, flares, filaments, and granulation.  H-Alpha filtering also gives the most "natural" view of the sun, in brilliant yellow, orange, and red.

 

 

Other than choosing a solar telescope based on the manufacturer, the most obvious decision you will make has to do with aperture.  As with all telescopes, size does matter.  The larger the aperture, or objective lens size, the greater the resolution of the image.  Choose the aperture that best suits your needs in regards to portability and price.

You will also want to pay attention to the system's bandpass.  Put in the most simplistic terms, the lower the bandpass, the more contrast you see on the solar disk.   Most single stacked h-alpha filters are at about <0.7 -< 0.8 Angstrom, which creates a good balance of detail on both prominences and the solar disk.  Double-stacking lowers the bandpass of the filter to about <0.5A, which will increase disk contrast but slightly decrease contrast and visibility of the prominences.   Most people are fine with this trade-off, as the results are pretty spectacular!

Changes in altitude and, to a lesser degree, temperature, may affect where the filter’s bandpass falls in relation to the Hydrogen-Alpha emission line.  A mechanical tuner (either tilt-type or air pressure) allows the user to tune the filter slightly to center it back on the H-alpha line.  This tuner, which is included on all solar telescopes and filters, is very helpful, especially when you take your telescope to a location that is higher, lower, hotter, or colder than “normal”.  Keeping your filter precisely tuned will result in sharper, higher contrast views.

A small number of solar telescopes (and filters) are tuned to the Calcium-K bandwidth, which reveals features different from those of H-Alpha.  Internal narrowband filters allow for a <2.4 Angstrom bandpass.  CaK telescopes are primarily used photographically due to the difficulty of seeing everything that CaK has to offer.  It is easy to tell the difference between an H-Alpha image and that of a CaK because CaK images will appear purple and blue.  The Ca II K line is a strong spectral line associated with once-ionized Calcium.  It has a wavelength of 393.4 nm (billionths of a meter, in the blue part of the spectrum) and absorbs about 98 percent of the light at its central wavelength.  In this spectral line, you view layers of up to 2000 km above the visible surface of the Sun.  The center of this spectral line is very sensitive to the presence of magnetic field in the material.  If magnetic field is present, then the absorption is less (i.e., more light is transmitted).  Moderately strong magnetic field shows up bright in images taken in this spectral line, but strong magnetic field (such as in sunspots) doesn't.  Typical CaK images show brightness along the edges of cells (called super granules) and in certain isolated areas (called plague).  When enough magnetic field is present, the plague are associated with sunspots and are then called active regions.

Read more