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(meteorobs) Re: Zodiacal light



Patti Smith wrote:
> 
> Mr. Linnolt,
> 
> Forgive me if this is a silly question, but I'm new to
> meteorobs and just a sky watcher (financial aid officer for
> a living), but by 'Zodiacal light", are you talking about
> what my husband & I have been seeing in the night sky since
> last summer...dot it looks almost like a particle/dust trail in
> the sky.  LOTS of points of light in a strip?
> 
> How can I get more info on this?
> 
> Thanks for your time if you have some!!!
> 

Hello Patti,

Welcome to the Meteorobs list. I think you will enjoy it, as it has a
great bunch of subscribers willing to help!

Regarding the Zodiacal light. It is a faint glow caused by the sun's
light reflecting off of the tiny interplanetary dust particles, which
tend to cluster along the plane of the solar system. This plane is the
ecliptic or "zodiac", the imaginary line in the sky, along which most of
the planets (except pluto, which is inclined much more than the others
out of this plane) , sun and moon travel. So, the Zodiacal light will
appear as a pyramid or cone starting at the point where the ecliptic
intersects the horizon, and following the ecliptic up in the sky. It is
brightest and widest right above the horizon, near to where the sun sets
or rises, and becomes fainter and narrower further along the ecliptic,
and is brightest just at the end of evening twilight, or before morning
twilight. Because, at that time, the sun is nearest to the horizon, and
therefore the glow is the highest and brightest in the sky. But still,
it is fairly faint, so you must wait until it becomes totally dark to
see it, and it is most easily visible when the ecliptic makes a high
angle with the horizon. That occurs around March for the evening and
September for the early mornings. It also helps to be at a lower
latitude, nearer the tropics, where the ecliptic stands higher in the
sky. Also, make sure that if you observe from the outskirts of a city,
the city lights are not in the direction of the sunset/sunrise,
otherwise you can mistake "light pollution" glow for it ! It is somewhat
similar in brightness to the milky way but more uniform or diffuse,
because it is caused by light reflecting off trillions of fine dust
particles, as opposed to the individual stars of the milky way.

The next months are good for observing it just after evening twilight
ends, and the planets Mars, Jupiter and Saturn are aligned along the
ecliptic in that order, from the west to the meridian, so it is easy to
picture it all. Also, the milkyway is sort of parallel to it, in the NW
as it passes from Cassiopeia to Cygnus. You can see both and compare how
they look if you gaze directly west.

I have an excellent view of it from here in Hawaii, and I will attempt
to get some good wide angle shots of it in the future, but it is
difficult to photograph, due to its diffuse nature.

Good Luck observing!
Mike Linnolt
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