May 28, 2008

10pm-2am

Around 10pm, I stuck my head outside and saw that the sky was beautifully, wonderously clear. Stars shimmered brightly in the firmament, a myriad of gently twinkling lights.  The sky was dark, allowing even the fainter stars to gleam like diamonds. The air was crisp (in the 50’s) and without a breeze. In short, absolutely perfect conditions for imaging. I really didn’t feel like taking the scope out, but having missed a few good nights over the weekend due to laziness, I felt I couldn’t let this one go in good conscience.  So, out came the scope. I used the DSI Pro and the focal reducer and planned initially to only image globular clusters in Hercules and Ophiuchus. However, as the images came in, I was struck by the truly excellent imaging conditions and decided to make a grand run of it, not concentrating on long-exposures of a handful of objects, but shorter ones of many.  A preview of the summer’s coming attractions. The Pro performed wonderfully, capturing detailed images of all my favorite objects. 

M13

This image is comprised of 30, 15-second sub-exposures.

M4

This is a loose globular cluster lying about 7,000 light years away in the constellation called Scorpius.  The cluster appears to lie just west of the bright red supergiant star, Antares, and can be easily spotted with binoculars, given a good view of the southern horizon.

This image was composed of 30, 15 second sub-exposures for a total exposure time of 7.5 minutes. 

M12 

This globular cluster, which lies in the constellation Ophiuchus (which means serpent-bearer in Greek) about 16,000 light years away.  The cluster is so loosely packed that it was once though to be an open cluster. Astronomers speculate that it may have lost as many as a million low mass stars as a result of gravitational interaction with the Milky Way.

M10

Another of the many globular clusters in Ophiuchus, M10 has a diameter of 83 light years and lies 14,300 light years away. Charles Messier discovered it in 1764, identifying it – as he did many other objects due to his telescope's poor optics – as a “nebula without stars.”

M17

The Swan Nebula in black and white.

M16

Perhaps best known to the public due to NASA's famous “Pillars of Creation” photo taken by the Hubble Space Telescope in 1996, which showed in extravagant detail the pillars of dust and gas at the nebula's heart, the Eagle Nebula is one of the summer sky's greatest jewels  

First noticed by French astronomer Phillippe Cheseaux about 20 years before his fellow countryman Charles Messier noticed it and added it to his famous catalog in 1764, M16 is an emission nebula surrounding an open star cluster (NGC 6011). The nebula lies in a region of active star-formation and is believed to have given birth to the cluster, which is estimated to be only 5.5 million years old. The “Eagle” - the dark structure at the nebula's heart which gives M16 is name - is composed of dust and gas and stands out against the emission nebula's bright background.  M16 is estimated to be about 7,000 light years distant.  The cluster can be easily discerned with a pair of binoculars, which will, on a clear night, also show a bit of hazy nebulosity. The “Eagle” structure is only visible in long photographic or CCD exposures. 

The preceding image was composed of 50, 15-second sub-exposures.

M20

The Trifid loses a little of its majesty when deprived of its luscious color, but the monochrome DSI Pro's greater sensitivity does reveal the incredibly rich star field in which the nebula lies, as well as more of the nebula's structure.

This image comprises a stack of 30, 15-second sub-exposures.

NGC 6888

Commonly known as the “Crescent Nebula,” NGC 6888 is an emission nebula in the constellation Cygnus. The nebula was formed about 400,000 years ago when successive waves of gas blown off by a nearby Wolf-Rayet star (a super massive star rapidly losing mass and possibly heading toward supernova), traveling at different speeds, collided with each other.  In very long exposures the colliding waves are eerily visible as hazy ripples.

This image was created by stacking 30, 15-second images. Longer and more sub-exposures will be needed to tease out more detail of the nebula's structure.

NGC 6992

This string-like stand of nebulosity in Cygnus is part of a larger structure often referred to as the “Veil Nebula” or “Cygnus Loop.” Together with other strand-like components – NGC 6960, 6962, 6979 and 6995 – NGC 6992 forms an arc of dust and gas that is all that remains of a massive star that exploded about 8,000 years ago. Material from the explosion - a supernova - has been expanding outward in a spherical shell ever since, slowly growing more diffuse as the shell expands. The nebulae in the loop are believe to be between 1,400 and 2,600 light years away and exhibit a fine, filamentary structure in long-exposure images. William Herschel first noticed the nebula in 1784. The Veil can occasionally be glimpsed in large telescopes, but CCD or photographic images are needed to truly see the nebulae.

During the course of the summer, I will attempt to image the entire Veil Nebula and create a composite image showing all of its components.

M27

Commonly known as the “Dumbbell Nebula” due to its hourglass shape, M27 is a planetary nebula that formed when a dying star blew off its outer layers of dust and gas in a type of explosion, called a nova, before shrinking into a white dwarf. The nova is believed to have happened between 3,000 and 4,000 years ago. The white dwarf is visible at the heart of the nebula. It lies about 1,360 light years away. 

M27 is a favorite of skywatchers, easily visible in binoculars and small telescopes as a hazy patch in the constellation of Vulpecula (Little Fox in Latin), which lies just south of the constellation of Cygnus. The nebula lies in a very rich starfield (which is, itself, one of the Milky Way's spiral arms). 

This image was composed of 30, 15-second images.

M8

About 4,100 light years away, toward the galaxy's center, in the constellation Sagittarius, lies on of the sky's most impressive star-forming clouds – the Lagoon Nebula.

Believed to be almost 150 light years across, the Lagoon nebula is an emission nebula with new stars forming at its center.  A small cluster of young stars (NGC 6530) is scattered in front of it, giving it an unrivaled appearance in the summer sky. The nebula is bright enough to be visible to the naked eye under dark conditions. It takes is name from its sprawling appearance, which is intersected by dark patches of dust and gas, some of which are collapsing to form new stars. 

This image is composed of 30, 15-second images.