Intimately connected with this band and with the zodiacal light is the Gegenschein, or counter-glow, a faint illumination of the sky in the region opposite the sun, which may generally be seen by a trained eye when all the conditions are favourable., Unfavourable conditions are moonlight, nearness to the Milky Way, and elevation of the light above the horizon (and therefore a depression of the sun below the horizon) of less than 20°, and the presence in the region of any bright planet.
From the description given of the zodiacal band and the Gegenschein, it is clear that these objects should be best seen at the highest elevation, especially within the tropics.
Another anomaly is that he never saw the Gegenschein, but describes the band as equally bright in all its parts, except near the horizon.
Barnard reports it as sometimes best seen when the sky is slightly milky, while during the observations already mentioned from the Rothorn the Gegenschein was scarcely, if at all, visible, though the conditions were exceptionally favourable.
The question whether the Gegenschein can be accounted for by the reflection of light from the same matter as the zodiacal band is still unsettled.
Wolf, Beobachtungen des Zodiacallichtes (1850-52); Brorsen Ueber den Gegenschein des Zodiacallichts (1855) and in Schumacher, 998; J.