Mars Opposition

Mars during the 2005 opposition
Mars during the 2005 opposition
Today the planet Mars will pass through opposition.

Closest approach of the two planets is not necessarily on the same day as opposition, but can vary up to two weeks. This year closest approach will occur March 5th with the two planets approaching to 99,331,411 km (61,721,554 miles) at 07:01HST. At this distance the red planet will show a disk 13.89″ arc-seconds across in the eyepiece.

All month Mars will be visible throughout the night, high in the sky at midnight. This is the time to enjoy observing our closest neighboring planet while it is nearby and high in the night sky.

A Cautionary Tale

At Keck we regularly move pieces of glass up to two meters across and weighing hundreds of pounds. These optics are nearly irreplaceable, visions of catastrophic damage to one of these pieces of glass is the stuff of nightmares. An observatory is built around the telescope, hundreds of tons of steel supporting the all important optics. While damage of any sort is a concern, much of the critical equipment can be repaired without major issue. It is the optics that are much harder and more expensive to replace. While these pieces of glass could be re-manufactured, it would probably take a year or more to accomplish.

Damaged Secondary
Damage to the Cerro Tololo Victor Blanco 4m f/8 Secondary. Image credit: CTIO
Last week the unthinkable happened at the Cerro Tololo Victor Blanco 4m Telescope in Chile. A secondary mirror was being removed from the telescope when the handling cart tipped over and injured two workers. Fortunately the injuries were not very serious. The secondary? It suffered severe damage, a 20cm crater in the front surface.

At Keck we had recently undertaken a full review of our optics handling procedures. Every step of the process, every piece of equipment was subject to scrutiny. The procedures reviewed by a committee of internal and external reviewers. The goal was to prevent just this sort of incident, to protect our invaluable glass.

Photos of the damaged CTIO secondary and descriptions of the incident are a powerful example of what can go wrong. Something that will be in the back of everyone’s mind next time we are moving a piece of big glass.

Venus and Jupiter

Tonight the two brightest planets in the sky will be almost exactly 3° apart. Jupiter will be shining at a brilliant -2.1 magnitude, even that will be outshone by Venus at an even more brilliant -4.3 magnitude. At 3° separation the pair will fit together in the field of a pair of binoculars or a rich-field telescope. If you miss tonight the pair will remain close for several nights, only 3°11′ apart tomorrow night, and 3°34′ apart on March 15th.

Take a look, it will be hard to miss these two brilliant planets high in the evening sky.

Kohala Dive Operations

Most of the Kona side dive operations operate out of Honokohau Harbor, giving access to dive sites from Kailua Bay to well north of the airport. These are the operations most divers visiting the Big Island are familiar with. The diving is good around Honokohau, but can be limited, island divers know that the character of the reef is different as you move north or south.

Experienced divers will often recommend diving the Puako and North Kohala reefs. Here the shoreline is notably older, where the volcanoes have not sent lava flows into the sea for many thousands of years. The reefs have had much longer to establish themselves, resulting in heavier coral growth and rich sea life.

If you want to try the sites further north, along the Kohala Coast, you need to choose another outfit to dive with. Two local dive ops operate along the Kohala coast, Blue Wilderness and Kohala Divers. Both outfits are small businesses, locally owned and operated, the owners often on the boat with you.

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Kohala Diving Guide

My March project is to move all of the dive guide articles over from the old blog. Most of them are already moved over, scheduled to post through this month. Copied and pasted over from the old blog, I have gone through them and updated the posts with current information. The series of blog articles provides a nice guide to anyone exploring the Kohala coast with the plan of getting in the water to snorkel and dive.

A Leap Day

Today is February 29th, that odd date that only occurs every four years.

The reason for a leap day inserted into the calendar, the existence of February 29th, is ultimately astronomical. Perhaps a little explanation is in order…

We originally defined days as the time it takes the Earth to rotate. While we define years as the time it takes the Earth to orbit once around the Sun. The problem is that these values do not divide evenly into one another.

Mauna Kea Sunrise
Sunrise seen from the summit of Mauna Kea
The Earth takes about 365.24219 days to obit the Sun, when measured by the Sun’s position in the sky, what is called a tropical year. There are different ways to measure a year, but if one is concerned with keeping the seasons in sync with your calendar, then you are interested in tropical years.

It is that bunch of decimals, the 0.24219 etc., that is the problem, every four years the count drifts out of sync by roughly one day. The insertion of an extra day every four years helps bring the calendar back into synchronization with the orbit of the Earth and with the seasons.

Even leap years do not quite fix the problem as 0.24219 is close, but not quite 0.25 or one quarter of a day. Thus additional corrections are needed… Enter leap centuries.

Our current calendar was instituted by Pope Gregory XIII in 1582, setting up a standard set of corrections for the fractional difference between the length of a year and the length of a day. Scholars knew that errors had been accumulating in the calendar for centuries, resulting in a drift of several days. Religious authorities were concerned that this drift had displaced important celebration in the church calendar, in particular the celebration of Easter. After much argument it was decided to reform the calendar. The current solution was devised by a number of astronomers, including Aloysius Lilius, the primary author of the new system.

The Gregorian Calendar uses an extra day in February every four years, unless the year is divisible by 100, then there is no leap leap day that year. However, if the year is divisible by 400, then it is a leap year. While this may sound odd, it does create a correction much closer to the ideal value of 365.24219 days per year.

Even this is not perfectly precise. The correction is close but will drift given enough time. The length of a tropical year also changes slowly over time. We will eventually have to add another correction to keep the calendar and the seasons in sync. But not for a few millennia, good enough, for now.

As 2012 is divisible by four, there will be a leap day added to the end of this February… Today.

MOSFIRE Arrives at Keck

W. M. Keck Observatory press release…

A 10,000-pound package was delivered on Feb. 16 to the W. M. Keck Observatory near the summit of Mauna Kea. Inside is a powerful new scientific instrument that will dramatically increase the cosmic data gathering power of what is already the world’s most productive ground-based observatory.

The new instrument is called MOSFIRE (Multi-Object Spectrometer For Infra-Red Exploration). It is the newest tool to survey the cosmos and help astronomers learn more about star formation, galaxy formation and the early universe. The spectrometer was made possible through funding provided by the National Science Foundation and a generous donation from astronomy benefactors Gordon and Betty Moore.

“This is a crucial and important step,” said MOSFIRE co-principal investigator Ian McLean of U.C. Los Angeles, who has been involved in the building of four instruments for the Keck telescopes. “Just shipping it to Hawaii is the first step.” A long series of installation steps are already underway that will lead up to MOSFIRE’s “first light” on the sky and handover to the Keck community in August.

Hauling MOSFIREThe truck carrying MOSFIRE was escorted by police, Mauna Kea rangers and Keck Observatory personnel as it climbed the last few thousand feet to the summit. Photo by Larry O’Hanlon

MOSFIRE will gather spectra—chemical signatures in the rainbows of light from everything from stars to galaxies—at near-infrared wavelengths (0.97-2.45 microns, or millionths of a meter). That’s light which is beyond the red end of a rainbow—just a bit longer wavelength than human eyes can see. Observing in the infrared allows researchers to penetrate clouds of dust to see objects that are otherwise obscured. It also allows for the study of the most distant objects, the spectra of which have been stretched beyond optical wavelengths by the expansion of the universe.

What sets MOSFIRE apart from other instruments is its vastly more light-sensitive camera and its ability to survey up to 46 objects at once then switch targets in just minutes – an operation that takes comparable infrared instruments one to two days to complete.

“I reckon that MOSFIRE will observe very faint targets more than a hundred times faster than has ever been possible,” says Caltech astronomer Chuck Steidel, MOSFIRE’s co-principal investigator. “All the observations that my group and I have done in near-infrared spectroscopy with Keck over the last ten years could be done in just one night with MOSFIRE.”

Steidel anticipates that MOSFIRE will be one of the Keck’s workhorse instruments, used for about half of all telescope time on the Keck I Telescope. “It’s opening up a whole new area of study.”

Another big asset of MOSFIRE is that it can scan the sky with a 6.1 arc minute field of view, which is about 20 percent of a full moon and nearly 100 times bigger than the Keck’s current near-infrared camera. To take spectra of multiple objects, the state-of-the-art spectrometer consists of 46 pairs of sliding bars that open and close like curtains. Aligned in rows, each pair of bars blocks most of the sky, leaving a small slit between the bars which allow a sliver of light from the targeted object to leak through. Light from each slit then enters the spectrometer, which breaks down the object’s light into its spectrum of wavelengths.

MOSFIREMark Kassis stands beside the MOSFIRE spectrograph

Because everything that’s even somewhat warm radiates in the infrared, all infrared instruments must be kept cold to prevent any trace of heat from the ground, the telescope, or the instrument itself from messing up the signal from space, MOSFIRE is kept at a cool 120 Kelvins (about -243 degrees Fahrenheit or -153 degrees Celsius). This makes MOSFIRE the largest cryogenic instrument on the Keck telescopes.

Astronomers will use MOSFIRE to study the epoch of galaxy formation, as well as the so-called period of re-ionization, when the universe was just a half-billion to a billion years old. The instrument will also be used to investigate nearby stars, young stars, how stars formed, and even brown dwarfs, which are stars not quite massive enough for nuclear fusion to ignite in their cores.

MOSFIRE will also allow astronomers to do riskier—but more scientifically rewarding—research, Steidel says. Taking the spectrum of a single star or galaxy involves precious telescope time and resources. But because MOSFIRE can observe many objects at once, astronomers can afford to take extremely long exposures. Otherwise, such long exposures of single targets would be difficult to justify with limited telescope time and other observing targets waiting in line.

Caltech’s Keith Matthews, who has built two previous Keck instruments, plays a leading role as chief instrument scientist. The team includes the engineering and technical staff of W. M. Keck Observatory, the technical staff of the UCLA Infrared Lab, optical designer Harland Epps of UC Santa Cruz and the staff of Caltech Optical Observatories.

The Moon and Pleiades

Tonight a bright half Moon will be just under 4° from the Pleiades star cluster. The Moon will be 43% illuminated, bright, but the cluster is bright enough to be seen even against a bright Moon. As the Pleiades move to the west over coming months there will be a few more lunar conjunctions, with increasingly smaller crescents.

Deep Violet, an 18″ f/4.5 Dobsonian

In April 2001 I realized a dream that had been many years in the dreaming and a year in the making, a large aperture dobsonian.

Deep Violet
Deep Violet set up near the Dragoon Mountains in Southern Arizona
The decision process that eventually settled on the 18″ f/4.5 design was a long one. As a very active amateur I had had many opportunities to examine other scopes. To see where they excelled or where they fell short. With this experience I eventually decided on a list of requirements.

  • The scope had to have sufficient aperture to take advantage of the dark skies available near Tucson. I wanted to see spiral arms in galaxies.
  • The design was to be visual only. No drives, but provisions for an equatorial platform at a later date.
  • The mount would be a no compromise rigid structure, capable of allowing good optics to perform at their best.
  • The scope had to fit through a standard doorway.
  • The scope had to fit in the cargo compartment of a Ford Explorer Sport without dropping the seat for safety during transport.
  • The eyepiece must not be an excessive distance above the ground, allowing use while standing on the ground much of the time. (But then, I’m 6’2″ tall)

Over a decade of engineering experience has taught me that a well defined set of specifications can make all the difference at the end of a project. With these design goals in mind the plan then progressed rapidly.

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