Canon 30D Unmodified with Astronomik CLS filter
9x300sec at iso 1600
30 Darks/Flats/Bias
Orion ED80 with WO 0.8 reducer/flattener

A widefield view of M57 in Lyra. It is pretty, though.

The eclipsing variable Sheliak is present at the right mid part of the frame. Located nearly 900 light years away, it actually radiates the visible light of 2000 Suns. The two stars, a bright bluish hotter one with a temperature of some 13,000 degrees Kelvin orbiting a dimmer white cooler one (though one still much brighter than the Sun) with a temperature closer to 8000 Kelvin. The plane of the orbit is pitched so that during an orbital period of 12.9 days each star gets in the way of the other, the combined light of the system at minimum alternating between 30% and half of normal every 6.5 days. Sheliak's variations are easily visible to the naked eye by comparing the star to others in the constellation.

June 12, 2007