Those Subtle and Maddening Solar Features!

by Nancy L. Thomas

I can honestly say I don't know what E. L. Trouvelot had in mind when he named
two solar features "veils" and "wisps". I can only make an educated guess. And a
thousand times I've asked Trouvelot (in an imaginary conservation), "Just what
did you see?"

According to Dr. Dorrit Hoffleit, many of Trouvelot's sketches and drawings are
now scattered or lost. At best, we are left with a vague description of the veils
and wisps.

The next two questions I mulled over were, "Why weren't these features being
observed more often and why weren't they common knowledge?" It is my opinion that
the following may offer an explanation.

> The telescope must be of sufficient aperture and I would tend to believe the
smallest practical size would be a 6 inch telescope.

> Magnification needs to be on the high side.

For example, I use a 7.5 Plossl on the 6 inch refractor and see the elusive
features via projection. The use of a Plossl eyepiece is not recommended. Using a
Huygens eyepiece would be preferable, however to prevent heat stress and damage,
I use more than one Plossl that can be "changed out" before the heat builds and
destroys the eyepiece.
 
Never look at the Sun, through a telescope, without taking the proper
precautions!

> The telescope need to be stopped down with an aperture mask or stop.
The 6 inch (f/10) is stopped down to f/30 with the help of a 2 inch hole in the
aperture mask or stop. The use of this device can also aid in protecting the
eyepiece from heat stress by keeping the eyepiece cooler.

> Observation of these features is best between 8:30 and 10 AM. The observer can
try between 3 and 5 PM, but will have to contend with heat turbulence caused by
the afternoon sun. Between the hours of 10 AM and 3 PM the sunlight is too strong
and has a tendency to "wash-out" these features even with the aperture mask or
stop in place.
 
> Lack of contrast.

The use of a black cloth or hood (over the head) will not only increase the
contrast while observing sunspots, but will also help with the observation of
veils and wisps.

> Another reason why observers may miss these features is because he/she is not
looking for them or possibly doesn't know of their existence.
Usually solar observation is directed at the more visible solar features, i.e.
sunspots.

> Lastly, the veils and wisps are so transient and changing in nature that they
can be easily overlooked.

I first learned of the veils and wisps after reading Peter O. Taylor's book
entitled Observing the Sun in March of 1995. Also, about this same time,
Deltona's premier solar observer urged me to stop the refractor down to f/30 and
it was then I started to notice a few hazy patches and streaks. Things really got
interesting when I started using a black cloth to help with contrast!
As I become even more familiar with the solar surface, I start to notice that
there was a lot more going on than just simple gray patches and streaks! And more
than the casual observer would notice!

By August 1995, I started to see a pattern beginning to form. I began to catalog
the more repetitive and complex solar features and will continue to do so
indefinitely.

Next came the morphology phase of the research. This included timings (down to
the second) and drawings illustrating the various changes the complex features
went through.

The next question that came to mind was, "What forces are causing these features
and making them change the way they do?"

Perhaps I found a small clue in a book that was graciously loaned to me and
entitled, Beginner's Guide To The Sun by Peter O. Taylor and Nancy L.
Hendrickson.

Could it be that convection, sound waves, turbulence or magnetism were
responsible for the evolution and actions of the veils, wisps, and the other
complex solar features I was now observing? At present, I just don't know as I
haven't the background in physics or theory.

Where will all this lead? I haven't the foggiest idea, but I do know the
researcher travels a lonely road. And until I can put together a team of
individuals who are gifted in observation, physics, theory, and photography, I am
assured and guaranteed that these subtle and maddening solar features will lead
me on ONE merry chase!