Our limiting visual magnitude is usually better than 6.5, and the gegenschein
and zodiacal light are often visible.
When we think of solar-system members and phenomena visible without optical aid, the list typically comprises the Sun, the Moon, five classical planets, Uranus, comets, meteors, auroras, the zodiacal light, and the gegenschein
. Bright comets are somewhat uncommon, and rarely do we know well in advance when they will arrive.
The zodiacal light, gegenschein
, and zodiacal band (S&T: October 2000, page 116) are all visible--the zodiacal light to a striking degree, and the zodiacal band spanning the entire sky.
We can sometimes glimpse a hint of it in the form of gegenschein
, a light hazy patch a few degrees across located directly opposite the Sun in the nighttime sky (S&T: October 2000, page 116).
Morehouse wrote of the gegenschein in his 1928 essay, "Reminiscences of Edward Emerson Barnard":
Barnard's rediscovery, and Swift's admission that he "never could see it," tells us much about the gegenschein. Time has not altered its mystique.
My first and best view of the Horsehead was in a hand-held 6-inch Newtonian at 36[yen] without a filter on a night dark enough to see the gegenschein
. I have found the Horsehead often since, usually with an eyepiece that yields an exit pupil near 4 millimeters.
Given the opportunity, Kanipe rattled off a laundry list of desires for a general planetarium program, including variable-star-magnitude estimates (and searching), orientations of double stars, accurate peaks for meteor showers, a "quantifiable" indication of twilight, and incorporation of the zodiacal light and gegenschein
At the Prude Ranch the gegenschein
is quite noticeable, and it is all but absent from Leakey.
The spectrum of the sky, however, is complicated by low levels of background glow from gegenschein
, zodiacal light, and diffuse light from the Milky Way.
Jim and I traced Hyakutake's mighty tail more than halfway across the sky - from Ursa Major, through Coma Berenices, to the gegenschein
east of Leo, and faintly as far south as Corvus.
For instance, some dark-sky observers admitted that the tail became lost or difficult to see once it entered the gegenschein
(a broad, dim glow in the sky opposite the Sun).
From Tucson, Arizona, "it went right through the gegenschein
and zodiacal band and out the southern side!" wrote Star Trails columnist David Levy on the morning of March 26th.