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Definition of Terms
Prominences — H-
α
emissions projecting beyond the limb of the sun, consisting of complex clouds or streamers of ionized
hydrogen above or in the Chromosphere.
Filaments - Prominences seen against the face of the sun, appearing as long narrow dark streamers or diffuse dark areas.
Active Region - Active regions are the result of enhanced magnetic fields and appear darker than the surrounding areas
with a roughly circular shape. Active regions show plage, sunspots, and flares.
Plage - Patchy H
-α
brightening on the solar disk, usually found in or near active regions, which can last for several days.
These are found in areas of nearly vertical emerging or reconnecting magnetic lines.
Sunspots - Spots of varying size usually consisting of a dark central region (umbra) and a lighter halo consisting of many
short fine fibrils (penumbra).
Flares - A sudden eruption of energy in the solar atmosphere lasting minutes to hours, from which radiation and particles
are emitted.
Chromosphere - An incandescent, transparent layer of gas, primarily hydrogen, several thousand miles in depth, lying
above and surrounding the Photosphere of the Sun and beneath the transition region of the Corona.
FOV - Field of View. This describes, in degrees, the area of sky one can see when looking through the eyepiece.
OTA - Optical Tube Assembly. This is the main body of a telescope.
H-
α
- A wavelength of light at 656.3nm or 6562.8 Angstroms (1nm = 1 billionth of a meter)
Angstrom - A unit of measurement for the wavelength of light. (1A= O.1nm)
Bandpass - A filter’s bandpass tells how wide a region of the light spectrum is transmitted around the primary wavelength.
The narrower the bandpass, the more surface detail becomes visible on the Sun. You can further narrow the bandpass of
your primary single stack filter by adding an additional filter of the same size to the objective. The term “double stacking” is
used to describe this process.
E.R.F. - Energy Rejection Filter. Prevents UV and IR light from entering the telescope.
Etalon - The heart of a Coronado filter. Composed of optics with tolerances 4 times tighter than those used in the Hubble
telescope.
Granulation - Small scale convective cell structures visible in white light (“rice grains”), best seen in apertures over three
inches, and in green light. Each cell consists of a brighter polygonal area of hot rising gas typically about 1100 km across,
and a cooler edge or “channel” of descending gas about 230 km wide.
