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Re: (meteorobs) Re: zodiacal light on Jan 03, 2001

On 9 Jan 2001, at 12:31, Robert Lunsford wrote:
 
> I have never seen a source of information on where to locate the
> zodiacal light on any particular night.

From the northern hemisphere, the ZL is best seen in the west 
from Feb-May after evening twilight, and in the east from Aug-Nov  
before morning twilight. Because in each case, that is when the 
ecliptic (=zodiac) is highest in the sky at about 90° solar 
elongation. 90° is typically the furthest extent of the ZL, beyond 
which it merges into the Zodiacal Band (ZB). The best time to 
catch it is just as evening twilight ends, when the spherical glow of 
twilight is replaced by the triangular wedge of the ZL.

> The zodiacal band rivals the winter Milky Way but is considerably fainter 
> than the summer Milky Way as seen from the Northern Hemisphere. 
> 

I have found the ZB to be even fainter than the winter milky way, 
but its brightness varies a lot along its length! In fact, calling it a 
"band" is misleading, making one believe it looks uniformly bright 
from end to end. In fact, it is brighter at the points where it merges 
with the ZL and the Gegenschein, and gets very faint and hard to 
see halfway between the Gegenschein and the limit of the ZL (at 
about 135° solar elongation).

All of these phenomena are better seen from tropical latitiudes. 
because there the ecliptic tends to be near the zenith at the 
favorable dates, and they are all so subtly faint that the extra 
atmospheric absorption at lower elevations really attenuates them 
severely. When I used to live in the mid latitudes, I hardly ever 
recall seeing them, but here in Hawaii they are very obvious, 
especially from the dark mountaintops. In fact the ZL is so bright 
that its a nuisance, preventing observations of faint comets or 
variable stars that happen to lie within its broad bounds!

Clear Zodiacal Observing!
Mike.

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