Thursday, November 25, 2010

False Dawn

Many have been fooled into thinking that it marks the start of morning twilight. Indeed the Persian astronomer Omar Khayyam referred to this ghostly glow as the "false dawn" in his poem, The Rubaiyat.

When false dawn streaks the east with cold, gray line,

Pour in your cups the pure blood of the vine;

The truth, they say, tastes bitter in the mouth,

This is a token that the “Truth” is wine.

Unlike the stars of the Milky Way, which stretch away from Earth for light-years, the source of false dawn lies between the inner planets of our Solar System. Billions of dust grains orbit the sun in a flattened disk spread out along the ecliptic. Many of these particles were ejected by comets. The dust reflects and scatters sunlight creating a visible triangular glow above the horizon.

It can be seen for up to an hour before true dawn begins to break. Unlike true dawn, though, there’s no rosy colour to the false dawn. The reddish skies at dawn and dusk are caused by Earth’s atmosphere, false dawn originates far outside our atmosphere. You are looking edgewise view into our own solar system.

The sub zero cold, early hours would bring this humongous Zodiacal Light right on schedule each night at Indian Astronomical Observatory, Hanle, Ladakh brighter than the Milky Way and rising to great heights. It was a sight to fix your gaze upon, one could never get used to it.

Hope this image conveys just a little of how I felt the 6 nights I was at that
wondrous place on top of the world.

Ajay Talwar
November 26th, 2010

Thursday, November 18, 2010

Kemble's Cascade

The constellation of Camelopardalis, no not a camel, but a Giraffe, is a northerly one surrounded by Cassiopeia, Perseus, Auriga, Lynx, Ursa Major, Draco & Ursa Minor. Milky Way wanders into the territorial area of the Camelopardalis towards the side touching Cassiopeia & Perseus. Camelopardalis contains a colourful asterism called Kemble's Cascade containing more than 20 stars, spanning more than 2½° in the shape of a cascade. The cascade contains colourful 8th mag stars leading to open cluster NGC1502.

Kemble's Cascade can be seen easily in binoculars. Start from Algol, proceed to Mirfak, the brightest star of Perseus and continue the same distance to locate Kemble's Cascade. Another way to locate it is using Cassiopeia. Start from Caph, head towards Segin and follow the same distance and direction to Kamble's Cascade. Caph and Segin are the two end stars of the W of Cassiopeia.

I shot this asterism through a 200mm lens from IAO, Hanle, Ladakh. Hope you like the photograph.