It's the Surface Stuff...
Changes in the large leading edge feature took a back seat to the
discovery of increasingly rich detail on the face of the sun. Changes
in the leading edge "fountains" occured overnight: loops gave way to
rising spires. As the day went on, the feature changed to a
relatively simple tripartate structure. By evening, it consisted
almost entirely of three elongated, rising(?), streaky clouds with
little visible interconnecting material.
The dark filament near the sunspot showed more and more detail. Here's
the outcome of the experiment proposed yesterday: the dark filament is
easily seen over a much wider range of wavelengths than the fainter limb
details and is at least apparent over as wide a range as bright knots
above the limb. For what it's worth.
[INSERT IMAGE HERE]
[It's late and the surface stuff is hard to draw!]
The dusky "surface" features were joined by bright features which were
subtle by comparison. Where the darkest portions of the filament
connected up with the surface of the Sun, the feature split off into
two or three darker strands. The effect was of cobwebs or of
cotton candy collecting in the solar "air."
With half an hour's inspection, I made out at least one other point of
apparent connection between this dark filament and the solar face. And
in a region I first thought unrelated to this filament, I saw a pair
of "spikes" which -- when the filter was tuned very finely -- were
sometimes darker than the penumbra of the spot. The spikes were
always lighter than the umbra. When I first glimpsed this structure by
peripheral vision, my first thought was that I had somehow overlooked
a second, trailing, sunspot group. But no: the spikes vanished
completely when the filter was tuned off band. In the process
of testing their visibility across different frequencies, I
made out a sinuous brightconnection running from them to the
very near the end of the large dark filament.
With these features to guide my expectations and my perceptions, I made
out more and more detail in the vicinity of the spot. The discovery of
such details was always easier with the telescope moving slightly.
The careful inspection of some specific feature usually also
benefitted from movement. I never managed to trace a dark feature
into an extension above the limb (though there are small prominences
showing some detail there today which were absent yesterday). I also
never succeeded in seeing just where a light feature merged or
transformed into a dark one -- which leads me to wonder if they really do
this or if the features are discrete, some brighter, some darker than
the surface of the Sun. The bright "river" seemed very likely to be
connected to the dark spikes rising from the Sun -- as if a single
physical object were seen differently -- but I am more dubious about its
continuation as the large filament. Where one faded and the other
appeared, a confused "wad" of light and dark features also sometimes
appeared.
I am sure that the darkest features changed rapidly: the spikes and
the darkest portions of the opposite end of the filament moved off-band
in the space of five minutes, sometimes to complete invisibility, but
more often just to relative obscurity. Sometimes they could be quickly
retuned (and returned) to their former darkness, but not always. Sometimes
you just had to check back later to see them again.
During one cloudy interlude, I prepared a test mask with the aperture
off-axis. Tuning the filter did indeed seem more effective then, with
the best views now not always with the filter's tilting
machanism jammed tight against its stop. Rotating the filter seemed to
produce nore dramatic and much more rapid differences in the "state of
tuning" for any given feature. Encouraged, I made up a better filter
holder -- from Butch Foster's surplus brass and the lid from another
coffee can. This one looks like a proper telescope part (at least from
the side): gleaming brass and flat black paint. Whether on-band images
are more contrasty is still up for grabs, but the state of tuning is far
more consistant across much more of the field of view, and I can now see
H-a features well at the center of the field rather than just in one
sweet-spot well out to one side of the field.
This gratifies the intuitive optical ray-tracer in my head (what
would Kahnemann and Tversky say?). 25 August 1996, 12:30 - 18:00 EDT.
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