H-alpha observation

12:00 noon 19 June 2005 PDT (2005-06-19-1900 UT)

The Sun was a bit more active today than yesterday. There were three
main groups of prominences. On the preceding limb, at a latitude of
about 60 degrees, was a moderate tuft, perhaps 3 Earths wide, but
sharpening to a point as it reached its full height of 4 Earths.

On the following limb was a broken prominence arch, its two bases
maybe 15 Earths apart, each only 3 or 4 Earths in height and in width,
pointing at one another. The southern base was about at the solar
equator; the northern base, therefore, about 15 degrees north. Setting
up just outside this broken arch, on both sides, were a sequence of
smaller prominences, each only about 1 Earth in size.

Also on the following limb, but about 50 to 60 degrees south latitude,
was a rolling prominence, extending about 15 Earths in length and 3 or
4 Earths in height, looking for all the world like an inverted Loch
Ness Monster. About another 15 degrees southward was a small hook,
extending out from the solar disc only about 2 Earths, and making a
hard turn toward the pole.

Interior to the LNM prominence were the only two prominent filaments
on the disc. About 0.9 radius out and to the north of the LNM was a
filament, about as wide as the LNM and parallel to it, and then at
about 0.7 radius and further north still (perhaps almost to the
equator) was a smaller triangular filament, about 5 Earths across.
There were other, smaller filaments scattered acros the disc, which
I won't bore you with.

I was struck, incidentally, by the sudden dimming and brightening of
some of the prominences, even though there were no clouds in sight,
and I didn't adjust the scope in any way. Does anyone know what might
cause that?

Equipment: Coronado SolarMax 40 filter on Tele Vue 70 mm Ranger, with
15 mm Plossl (32x). Seeing was about 3 arcseconds and fast, good
transparency (I make out the sky to reach about half maximum saturation
at about 30 degrees).

Brian Tung <brian@xxxxxxx>
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.