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.

May 25, 2008

After a long, long siege of rainy, cloudy weather and clear nights ruined by a bright moon, clear dark skies return.

The LXD75 was aligned with Polaris and Vega, now rising above the tree line by 9:30pm.

M20

I decided to use the DSI-C (a color camera) and the focal reducer to capture a wide-angle view of the nebula. While the DSI Pro (a monochrome camera) is much more sensitive and give better resolution, the Tridid's beautiful interplay of colors simply demands a color image.

M20 is composed of both a bright emission nebula (the red part) and a dimmer reflection nebula (the blue-ish cloud below the red), which actually surrounds the emission nebula. Messier discovered the nebula in 1764, describing it as a cluster of young stars surrounded by a nebula. Herschel noted its segmented nature – caused by dark dust lanes which extend in front of the emission nebula - and listed it as four separate items. It was Herschel who gave the nebula is famous name.

Estimates on the nebula's distance vary, but 5,200 light years is a commonly accepted number.

M17

Commonly known as the “Swan Nebula” because of its distinctive shape, M17 was first discovered by Phillippe Cheseaux some years before Messier rediscovered it and listed it in his catalog in 1764.

The nebula is illuminated by hot, young stars inside it. Estimated to be 40 light years across and about 5,000 light years away, the Swan is occasionally visible to the naked eye as a faint smudge in the constellation called Sagittarius.

April 30, 2008

M94

A spiral galaxy in the constellation Canes Venatici (the Hunting Dogs). Discovered in 1781 by Charles Messier's colleague Pierre Mechain.  M94 lies about 16 million light years away.

This image comprises about 80, 15-second sub-exposures.

April 29, 2008

The following images were taken without notes, so I don't recall the sky conditions, or exposure times, though I believe these images all comprise stacks of more then 80, 15-second sub-exposures.

M88

One of the brightest spiral galaxies in Virgo, it was discovered in 1781 by Messier, who described it as a “nebula without stars.” M88 is one of my favorite targets, though I don't image it nearly enough.  The galaxy stands out very prominently in even one second preview images, and fine details of its spiral structure can be discerned even in only 15-second exposures.

M88 is thought to have a linear diameter of about 130,000 light years and lies about 60 million light years away.

M63

You can never get enough of the Sunflower.

April 22, 2008

M13

A stack of short sub-exposures using the DSI-C.  This image was actually taken at the end of the imaging session as clouds were beginning to cover the sky.

M58

One of only four barred spiral galaxies in the Messier Catalog, M58 is one of the brightest galaxies in the Virgo Cluster. Discovered and cataloged by Messier in 1779, it was identified as a spiral by Lord Rosse.

It is currently thought to be about 60 million light years distant.

April 17, 2008

9pm-12am

A truly clear night, almost warm.  The moon, however, is high in the sky and three quarters full, its brilliance nearly drowning out the fainter DSO's.  In a few days, it will be full and I will need to wait until it wanes before resume imaging sessions.

The scope was first polar aligned – but not too well, I'm afraid – using Polaris and Arcturus, and the realigned using Arcturus and Regalus. The tracking was okay, and delivered object to the FOV most of the time in GOTO, but I could only expose for 15 seconds before getting movement in the image.

M65

With the bright moon so close by, this galaxy was almost lost in the glare.

60, 15 second sub-exposures were stacked to create this image.

M97

I continue to try and capture the Owl, but 15 second sub-exposures just aren't cutting it – and the bright moon didn't make it any easier. 

This image is composed of 86, 15-second sub-exposures. 

M99

For once, a decent image. 

Compared to the image I took a couple of weeks back, this stack of 100, 15-second sub-exposures shows an incredible amount of detail in the spiral arms – despite the moon's interference.  The difference between this photo and the previous one is a much finer focus. 

M91

Discovered by Charles Messier in 1781, M91 is a barred-spiral galaxy.  While it possesses a relatively bright core, the spiral arms and the “bar” connecting them are quite faint and difficult to record. 

This image is a stack of 86, 15-second sub-exposures.  Obviously, longer and more subs will be needed to capture the spiral arms in any detail.

M104

I always wait too long before getting around to the Sombrero.  By the time I swung the scope toward Virgo, this galaxy was already headed for occlusion by the treeline.  So I didn't have enough time to image it properly – as usual.

Still, the central dust lane is remarkably visible.  The trick will be to capture detail within the dust lane itself.  In order to do that I will need to increase the magnification.  This photo, like all the others, is taken with the LXD75 at f/5.  Barlow lenses would increase the f-ratio to f/10, but I don't know how well that would work with the DSI.

60, 15-second sub-exposures were stacked to create this image.

M13

The largest and brightest globular cluster in the northern sky.

This is almost certainly the best image I have ever obtained of M13 and shows just what the DSI Pro is capable of – if it has a good focus.

M13 was first discovered by Edmund Halley – the discoverer of Halley's Comet – in 1714 and was added to Messier's catalog in 1764. It is thought to have a diameter of about 145 light years, into which are squeezed several hundred thousand stars. Astronomers place its distance from Earth at about 25,100 light years.

April 14, 2008

9pm-12am

The sky was mostly clear for a good part of the night before finally clouding over completely.

M106

Another attempt.  Unfortunately, my tracking and alignment wasn't as good as it should have been, resulting in skewed stars.

This picture is a stack of 50, 21.2 second sub-exposures.  The galaxy's central disk stands out well, offering some detail of the star clouds swirling around the bright core. A dimmer halo of material surrounds the galaxy, just barely visible in this image. Longer and more sub-exposures should bring that detail out.

M109

I will not let the season pass without obtaining a good shot of this galaxy.  But if I am to do that, I will need considerably longer sub-exposures than I am using. 

While this stack of 80, 15-second sub-exposures shows the shape of the galaxy's spiral arms well enough, if fails to bring out any detail.  With M109 now reaching zenith just as the sky darkens at night, I won't have much longer to capture this galaxy unless I resort to moving the telescope out onto the front lawn, which is more effort than I'd like to put into getting the image.

M104 

Another galaxy that I really want to capture in detail before the season passes.  Yet, as with the others, I haven't yet applied long enough sub-exposures, or stacked nearly enough to reveal the fully amount of detail that the DSI Pro can capture.  

The poor tracking and alignment is quite visible here.