Monday, July 14, 2014

The Sun

Diameter: 864,000 miles
Volume: 1.3 million Earths
Inclination to Ecliptic: 7.25 degrees
Length of Day: 25.38 Earth Days
Surface Temperature: 5500F
Atmospheric Temperature: Up to 1,000,000F
Composition: Plasma
Atmospheric Pressure: .06% Earth
Atmospheric Composition: hydrogen, helium
Notable Exploration: Pioneers 5-9 (1959-68), Helios 1 and 2 (1975-1985), SOHO (1995-present), SDO (2010-present)

First of all, this should go without saying, but NEVER look at the Sun without specialized eye protection, whether it be in the form of eclipse glasses or solar filters for binoculars/telescopes. For penny pinchers who do not want to use eclipse shades, a #14 or darker welder's shield will work when observing the Sun with the eye alone. When looking at the Sun with the naked eye, it will often appear as a single-colored disk save a few large, dark sunspots. When turning binoculars and even or powerful telescopes on the Sun, the spots will appear more detailed, with clear shapes becoming visible.

In telescopes, the real fun starts when moving out of visible light into very specific wavelengths, which can be isolated by the use of wavelength-specific filters, which can be used to bring out specific details.

White Light
The cheapest and most simple solar filters, white light filters simply block out all but 0.001% of the incoming sunlight. The result is a dramatically dimmed solar disc that allows the viewer to now see surface detail in the form of sunspots, which are cooler (and thus appear darker) regions of the Sun that are caused by a twisting of magnetic fields in and around the Sun. Due to different materials used in the manufacturing process, the Sun can appear yellow, white, or even bluish in color.

Hydrogen Alpha
Hydrogen alpha (Ha) filters only transmit a deep red light given off by hydrogen atoms at a wavelength of 656.3 nanometers. The end result of this type filter is red Sun with easily visible granulation that turns the blank disc seen through a white light filter into a seething cauldron at the expense of rendering sunspots invisible. Another benefit: the ability to now see flames on the solar limb.

Calcium filters, like Ha filters, only transmit light at a very specific wavelength, this time at 393.4 nanometers. The interesting implication here is that the color one sees on the Sun mirrors the magnetic field strength. Result: the Sun will appear as a blue-violet disc but points of intense magnetic activity will appear white.

Now, while there are other types of solar filters out there, the above 3 are those that are economical enough to be bought by amateurs.

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