re zodiacal light 1

[jan lameer]

Eh, I think Wiebke made a mistake by accident; the zodiacal light is best seen in the northern hemisphere in spring in the west in the evening and in autumn in the east in the morning.

That is when the ecliptic makes the largest angle with the horizon at the end or beginning of twilight. The same goes with seeing Mercury. In those months, after sunset or before sunrise, the sun is deep under the horizon while regions near the sun are allready or still above the horizon.

[jan lameer]

Under good circumstances, like being in subtropical latitudes (Arizona, Tunesia, South Africa and the like) the zodiacal light is many times brighter than the milky way. It shines like a huge pyramid. Under true dark skies, like the desert in those places, you can even see the zodiacal light surround you and it gets brighter at 180 dgrees from the sun. Here you see pure reflection of sunlight against the small sand and dustparticles.This light is called Gegenschein or counterglow. It measures about 30 x 20 degrees. At dark nights in the Alps or you can see it easily when there is no milky way in the same place.

The same principle of the Gegenschein can be seen on the moon when it is in opposition with the sun: it brightens dramatically during true full moon.

[jan lameer]

The fun thing about zodiacal light is that most of you probably have seen it often but haven't realised it. Go to a dark location and know exactly when for that date and location astronomical twilight ends (evening) or starts (morning). All the light near sun is zodiacal light. But you needa true dark location for this. I've often been fooled in thinking that my watch was wrong, I thought twilight was still going on or had started an hour and a half before it should. The same by the way goes with aurora. Here at Terschelling we have grey nights in Summer, that is, twilight doesn't end at night. When in spring aurora happens, a lot of locals think: hm, summer has started early this year...

[jan lameer]

end of message in 3 parts, long messages don't get through *o.T.*

[Wiebke Fock]

Hallo Jan,

I was so happy that I could give an explanation for the Zodiacallight (mostly I’ve only got questions to the forum-members and no answers) so I exchanged autumn and spring and in the morning and in the evening by mistake. Thanks for correcting me.

Greetings
Wiebke

(I hope my English is not too bad)