| |
Jump
to: Intro, Safety & the Telescope, Filters, Diamond Ring
Effect
INTRO:
When looking at the sun, one must always do it safely. Most of
the time, the sun is much too bright to look at directly. Read on to
learn how to observe the sun without damaging your own eyes. By
pointing your telescope at the sun on a sunny day, you can see
exciting things happening. You can see the sunspots, filaments,
prominences, and the changes that are occurring from day to day.
It is only during total solar eclipse that one can look directly
at the sun without filters. When we look at the center of a solar
disk, we are looking through gas, much like the effect when looking
through fog. When we observe the edge of the sun, or the solar limb,
we are looking diagonally through the solar atmosphere and through
even more gas that obscures the view. Near the sun’s edge, we
see higher levels of sun’s atmosphere. Since these higher
levels are slightly cooler than the lower levels at the center, the
sun’s surface looks a little darker towards its limb.
Through the Earth’s atmosphere, the different colors of
sunlight are bent in different amounts. This is known as refraction,
and is most extreme at sunrise, sunset and green flash. It usually
lasts about two seconds and can be seen when the view of the sunset
is completely unobstructed. It is easiest when looking over water or
from a mountain without haze or clouds on the horizon. A green flash
is like a mirage, caused by bending light rays by air of different
temperatures. As the sun nears the horizon, because different colors
of rays bend by different amounts, we see overlapping images of the
sun. The colors are in rainbow order, but the blue, indigo and
violet are scattered so much that they don’t reach us. The
orange and yellow are absorbed by the ozone and water vapor, leaving
red and green. The mirage effect distorts the image. When the red
image sets, we see a brief bit of green on the horizon.
top...
SAFETY & THE TELESCOPE:
The
safest way to look at the sun is to not look at it directly at all.
You can use a telescope or binoculars with the eyepiece to project
the image on to a piece of cardboard. This is called, eyepiece
projection. In order to do this, stand with your back to the sun and
look at the cardboard. Do not look at through the telescope or
binoculars. Looking at the sun through the telescope for even a
second could be enough to cause blindness. Adjust the eyepiece of
your telescope so that it is behind its normal position. This way,
one can then vary the position of the eyepiece and the distance of
the paper to focus the sun’s image. An image as wide as a hand
would be enough to see the sunspots. You can trace the outlines of
the sunspots daily and follow the way they change as the sun
rotates.
top...
FILTERS:
The sun is about one million times brighter than the moon. Due to
the brightness, we would need a filter to see sunspots. The filter
must cut 1/1,000,000 of the sun’s rays. These filters are made
by telescope manufacturers. They go over the front end of the
telescope so that most of the light does not pass through.
There are some parts of the sun’s atmosphere that are not
visible in white light. Those parts can be seen when the unique
color of hydrogen is isolated. The light is called the H-alpha line
and falls in the red part of the color spectrum. Professionals have
filters that can pass this H-alpha line.
By looking at the sun with an H-alpha filter, we are actually
looking at the sun’s chromosphere. The chromosphere is made up
of spikes of gas, called spicules. These spicules rise and fall in
fifteen minutes. When looking through the filter, the solar surface
looks multicolored and dark lines form, known as filaments. When a
filament is rotated so it seems as if it at the edge of the sun,
known as a prominence.
top...
DIAMOND RING EFFECT:
The diamond ring effect comes from the last portion of light
shining through a valley on the moon. When it is over, we see a
corona, a halo of light around the sun. The corona is a layer of gas
surrounding the sun. It is a million times fainter than our own sky.
For us to be able to see the corona, the sun must be up when the sky
is not illuminated-which is exaclty what occurs during a solar
eclipse.
The corona has an irregular shape with streamers that
extend millions of kilometers. The sun acts as a magnet, allowing us
to see polar tufts, which are thin rays that come out of the sun's
poles.
top...
|
|
