from The Century Dictionary.
- noun The frequency or abundance of sun-spots, which varies in a semi-regular manner from year to year.
Sorry, no etymologies found.
A comparison of light-curves with curves of spot-frequency leaves no doubt on this point, and the strongest corroborative evidence is derived from the emergence of bright lines in the spectra of long-period variables rising to their recurring maxima.
The district of greatest prominence-frequency covers and overlaps by several degrees that of the greatest spot-frequency.
"light-curve," or zig-zagged line representing on paper the varying intensity in the lustre of certain stars, and the similar delineation of spot-frequency; the ascent from minimum to maximum being, in both cases, usually steeper than the descent from maximum to minimum; while an additional point of resemblance was furnished by the irregularities in height of the various maxima.