The Flight of OSIRIS
An incredible amount of planning and work went into the job, with everything culminating in a few days of frenetic activity. Often referred to as “twins”, the Keck telescopes seem anything but. Over the years these once identical twins have taken on their own characteristics. One of the things that differentiates the two, each has its own set of unique instruments. Cameras and spectrographs, these multimillion dollar devices allow the recording and studying of the light collected by the massive 10-meter mirrors. This week we moved one of these instruments from Keck 2 to Keck 1… OSIRIS.
OSIRIS is an infrared integral field spectrograph. Designed to take full advantage of the Keck Adaptive Optics systems, the instrument has a relatively small field of view. Within that small field it does amazing things, providing a simultaneous spectrum and image of an object. Essentially it takes a stack of images at the same time, each at a different wavelength. This gives astronomers a very powerful tool. One image will show the distribution of particular elements throughout an object. Using doppler shift, an astronomer can also observe how everything is moving within the object as well.
The Keck crew lowering OSIRIS into Keck 1 AO
Moving an instrument is not a trivial job. It is not simply a matter of unplugging the instrument and moving it to the other telescope. Each instrument has a tremendous amount of infrastructure required to support it. Electrical wiring, optical fibers, plumbing for the cooling systems, support computers, and more… All of it has to be moved.
OSIRIS has been a removable instrument, mounted to a handling cart for easy removal and installation into the telescope. The new installation will be a permanent mount within the AO enclosure. A new mount must be designed and fabricated. New support beams welded and bolted into place. There are openings to be cut into the floor for the mounts and support connections. Then all of the electrical, optical cabling and plumbing run through the structure of the telescope. This all has to be designed, reviewed and then the modifications performed without interfering with nightly observing. The amount of work is truly daunting, and thanks to the efforts of a great crew, now complete.
Keck Observatory Astronomer Wins Top Award
W. M. Keck Observatory press release…
A Keck Observatory astronomer who led the way to the discovery of a super-massive black hole at the center of our galaxy has been recognized this week with the 2012 Crafoord Prize in Astronomy, an award almost as prestigious for astronomers as a Nobel Prize.
“This is a big one. I’m thrilled,” said Andrea Ghez of the University of California at Los Angeles. For more than 16 years Ghez and her team have been pushing the frontiers of high-resolution imaging technologies with the twin 10-meter Keck telescopes in order to explore the center of the Milky Way. By tracking the rapid, small-scale orbits of stars at the Galactic Center, they discovered the presence of a source of tremendous gravity – the best evidence yet that a supermassive black hole exists there. The reality of such an object confronts and challenges our knowledge of fundamental physics.
Continue reading “Keck Observatory Astronomer Wins Top Award”
Most Distant Dwarf Galaxy Detected
W. M. Keck Observatory Press Release…
Scientists have long struggled to detect the dim dwarf galaxies that orbit our own galaxy. So it came as a surprise on Jan. 18 when a team of astronomers using Keck II telescope’s adaptive optics has announced the discovery of a dwarf galaxy halfway across the universe.
The new dwarf galaxy found by MIT’s Dr. Simona Vegetti and colleagues is a satellite of an elliptical galaxy almost 10 billion light-years away from Earth. The team detected it by studying how the massive elliptical galaxy, called JVAS B1938 + 666, serves as a gravitational lens for light from an even more distant galaxy directly behind it. Their discovery was published in the Jan. 18 online edition of the journal Nature.
Light Pollution Filters
Our neighborhood is a somewhat odd case. A large development surrounded by miles of empty land. Get just outside the neighborhood and the skies are quite dark. Inside the neighborhood one has to deal with the usual house lights and a plethora of streetlights. Still, I can see the Milky Way from the driveway, pick out M31 with the unaided eye, and make out a number of star clusters. There is one streetlight directly across the street from my front yard. A notable problem, only partly dealt with by way of a strategically planted Royal Poinciana. A few years old now, the tree has begun to shade the driveway from the worst local light source.
Despite the fact that the neighborhood is disgustingly overlit, there is a mitigating factor. All of the streetlights are low pressure sodium type lights. These lights emit all of their power at 589nm, a sharp emission which can be filtered at the camera. Filters for this and other common light pollution wavelengths are readily available from several manufacturers in a number of sizes and formats.
One minute Orion without LPR filter
While taking some wide field shots using a 50mm lens I had recent opportunity to see the difference with and without the filter. I did not have a filter that fit the 52mm thread on the lens, but rather simply set my 48mm filter on the front of the lens. I had not performed this simple experiment before as the usual mounting location of the filter is buried inside the setup. On this occasion it was a simple matter to take identical frames with and without the filter.
The resulting frames can be seen at the left. These are taken from the camera raw images, imported with daylight color balance, cropped and sized for display. Both images have been handled identically. Neither is a “pretty” picture, these are unprocessed images, none of the stacking, stretching and sharpening that would vastly improve the visual appearance.
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Postcard from the Reef – Leaf Scorpionfish
Dave spotted it, what appeared as a piece of debris lying in the coral. A closer look showed this ‘debris’ has fins. It is a Leaf Scorpionfish crouching low in the coral. I have seen a few members of this interesting family lately, often challenging to spot.
Lunar Apogee and Perigee
Does the Moon seem a little larger and brighter than usual? It may not be an illusion, sometimes the Moon really does look a little larger or smaller in the sky.
Like all orbiting objects, the Moon does not orbit in a perfect circle, but rather in an ellipse. This means that as it orbits it is a little further away or a little closer. In the case of the Moon the difference is not much, but you can see it, if you know to look.
The period of time between full Moons, the synodic month, is about 29.5 days. While lunar perigee occurs every 27.5 days, an anomalistic month. Since these periods are not equal, the cycle drifts in and out of phase. About once a year the cycles coincide and full Moon and apogee or perigee will occur near the same time.
At apogee, the Moon will be appear about 29 arc-minutes in size, a little less than half a degree. At perigee the Moon will be about 33 arc-minutes across, a bit more than half a degree. The numbers may not seem like much, but it is a visible difference. The simulated images shown here will give a better idea of what the numbers represent.
This change in size and distance leads to the moonlight being a bit brighter at perigee than at apogee, about a 30% difference. So if that moonlit night seems brighter than you remember it may actually be the case.
Saturnine Storm
This picture, captured on Feb. 25, 2011, was taken about 12 weeks after the storm began, and the clouds by this time had formed a tail that wrapped around the planet. Some of the clouds moved south and got caught up in a current that flows to the east (to the right) relative to the storm head. This tail, which appears as slightly blue clouds south and west (left) of the storm head, can be seen encountering the storm head in this view.
Laser Return Photometery
A different use for amateur astrophotography gear.
An amateur CCD camera can do more than take pretty pictures. There is no reason why any decent telescope, however small, and a CCD camera can not be used to do real science, or real engineering in this case.
The goal of the night was to perform proper photometry on the laser returns with independent equipment. We want to quantify the performance of the Keck adaptive optics laser systems. We launch two powerful lasers into the sky, one from each telescope, to allow analysis of the atmospheric distortions through which the telescope is observing. Using the data the system can correct for this atmospheric distortion and create much sharper images of distant stars and galaxies.
The lasers pass through a layer of sodium atoms about 90km (55miles) above the ground. There the 589nm yellow light excites these sodium atoms creating a glowing beacon, what we call the laser return. This return is what we look at to analyze atmospheric distortion. A brighter return allows better data and better performance of the system.
Both the Keck 1 and Keck 2 lasers in operation under the light of a nearly full Moon
Amateur astrophotography gear is perfectly capable of doing this task. A portable telescope, a proper CCD camera, combined with care to acquire calibrated images. All that I needed to add to the setup was a photometric V filter.
It was a perfect night for it, clear, dry and cold. Best of all, there was no wind to bounce the telescope around and chill anyone working outside. The winds are nearly constant atop at 14,000ft peak, calm nights are unusual, I was lucky indeed.
I setup the telescope atop a crust of ice and snow. The snow was convenient as it allowed me to set down gear on a cleaner surface than the gritty volcanic cinder underneath, keeping everything quite a bit cleaner. The altitude and cold made setup and breakdown a slow, laborious process, and added unique difficulties. I had to be very careful moving the heavy gear, so as not to slip on the icy snow. When I went to move the telescope tripod I found it frozen into the snow and cinder! I had to heave hard to break it free.