faculae 光斑，耀斑
　
Bright areas of the solar surface associated with sunspots and prominences.
　
　
fall 落隕石
　
A meteorite seen to fall. (See find.)
　
false color 假色
　
A representation of graphical data in which the colors are altered or added to reveal details.
　
field (gravitational, electric, magnetic) 場
　
A way of explaining action at a distance. A particle produces a field of influence to which another particle in the field responds.
　
filar micrometer 動絲測微器
　
An instrument that permits precise measurements at the telescope of the position of visual binary stars and similar objects.
　
filtergram (filter) 濾鏡
　
A photograph (usually of the sun) taken in the light of a specific region of the spectrum -- e.g., an H-alpha filtergram
　
find 尋隕石
A meteorite that is found but not seen to fall. (See fall.)
fission hypothesis 分裂假說
The theory that the moon formed by breaking away from the earth.
flare 閃焰耀斑
A violent eruption on the sun's surface.
flash spectrum 閃光譜
The emission spectrum of the chromosphere that is visible for the few seconds during a total solar eclipse when the moon has covered the photosphere but has not yet covered the chromosphere.
flatness problem 平坦問題
In cosmology the circumstance that the early universe must have contained almost exactly the right amount of matter to close space-time (to make space-time flat).
flat universe 平坦宇宙
A model of the universe in which space-time is not curved.
flocculent 叢毛狀的
Woolly, fluffy; used to refer to certain galaxies that have a woolly appearance.
focal length 焦距
The distance from a lens to the point where it focuses parallel rays of light.
focus (of an ellipse) 焦點
One of two points inside an ellipse that satisfy the condition that the distance from one focus to any point on the ellipse to the other focus is constant.
forward scattering 往前散射
The optical property of finely divided particles to preferentially direct light in the original direction of the light's travel.
　
frequency 頻率
　
The number of times a given event occurs in a given time; for a wave, the number of cycles that pass the observer in 1 second.

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