Palomar Skies

Support Your Local Mirror

2008-05-24T08:51:00.000-07:00

The Hale Telescope's 14.5-ton mirror is honeycombed on its underside. The triangular pieces are hollow to reduce the weight of the Pyrex disk. The round areas are the locations of the mirror supports.

The mirror supports are truly remarkable devices. From The Perfect Machine: "The thirty-six supports were precision machines, an assembly of levers, counterweights, gears, and ball bearings like a fine wristwatch, but large enough that it took two men to carry each of them."

"The design of the support mechanisms was clever. The levers of the mechanisms were designed to push up, against the tops of the pockets in the back of the disk, to counteract the force of gravity pulling down on the disk. The supports were four inches behind the actual surface of the disk."

Each of the 36 mechanisms has 33 different places where something can rotate, slide, or pivot (That's 1188 degrees of freedom!) to change the tension on the surface to ideally keep the mirror in its perfect parabolic shape.

All of this happens by gravity alone, there is no active control (Maybe someday, but not now). As the telescope pivots to point to a different location in the sky the pieces within the supports relocate and change their tension on the mirror.

Over the years pieces within the mirror supports can bind up a bit, limiting how easily the parts can move and how effectively the mirror's shape is maintained. During the recent engineering run one of the mirror supports was removed and examined in great detail.

Here is a photo of the mirror cell with the instrument removed from the Cassegrain cage. The big hole at the top is the where the light comes through to the science instrument. The red fans are fans that can blow air on to the backside of the mirror to help the mirror reach the proper temperature. All of the rest of the openings on the mirror cell are locations of mirror supports.

A close-up photo of one of the mirror supports.

More on the mirror supports and something that may surprise you later.

A Supernova Caught in the Act!

2008-05-21T10:06:00.000-07:00

A long time ago, in a galaxy far, far away . . . . there was a star that exploded. 90 million years later astronomers observed the event with telescopes located on both on Earth and in Earth orbit.

The galaxy is known as NGC 2770, found in the constellation Lynx. Back in December the supernova, SN 2007uy, was observed. That in itself isn't too amazing as new supernovae are observed in various galaxies relatively often. Within one particular galaxy they aren't too common, perhaps occurring once or twice per century.

On January 9th former Caltech astronomers Alicia Soderberg and Edo Berger, now with Princeton University was observing the supernova with NASA’s Swift satellite when they caught a new one, located within the same galaxy, in the act of exploding.

Of the many thousands of previously observed supernovae, this was the first one actually observed as the explosion was taking place. Most of them aren't caught until hours, days or weeks after the event. The discovery will be described in a paper ("An Extremely Luminous X-ray Outburst Marking the Birth of a Supernova") to be published in tomorrow's issue of the journal Nature.

A veritable fleet of telescopes, on Earth and in space, were quickly called into action to observe the new supernova, now known as SN 2008D. Caltech's observations were led by Shrinivas Kulkarni, MacArthur Professor of Astronomy and Planetary Science and director of Caltech Optical Observatories. Caltech astronomers including graduate student Bradley Cenko and others undertook detailed observations with the automated Palomar 60-inch and the 200-inch telescopes.

Captured by the Palomar 60-inch telescope, here is NGC 2770 with both of the supernovae marked:

Image Credit: A. Rau (Caltech)

Joining Swift and the Palomar telescopes in making observations of the event were the Hubble Space Telescope, the Chandra X-ray Observatory, the Very Large Array in New Mexico, the Gemini North telescope in Hawaii, the Keck I telescope in Hawaii, and the 3.5-meter telescope at the Apache Point Observatory in New Mexico.

What have we learned? This particular supernova was produced as the core of a massive star collapsed likely producing an ultra-dense neutron star. The newborn neutron star then rebounded, triggering a shock wave that blew the stars outer layers off and into space. Swift caught the flash of X-rays produced as the star blew apart.

The observations also show that SN 2008D is an ordinary Type Ibc supernova, which occurs when a massive, compact star explodes. Significantly, radio and X-ray observations confirmed that the event was a supernova explosion, and not a related, rare type of stellar outburst known as a gamma-ray burst.

Be sure to check out the Caltech press release and the NASA press release on the findings.

And Then There Were Two

2008-05-16T06:44:00.000-07:00

The Thirty-Meter Telescope (TMT) is one step closer to reality. After years of study, the site selection team has narrowed the search to just two possible sites to build what will be come the world's largest telescope. They are Cerro Armazones in Chile's Atacama Desert, and Mauna Kea on Hawai'i Island.

Each site offers the excellent conditions needed for an observatory of this magnitude. What's required? A high elevation; clear skies; stable, non-turbulent air; and a dry atmosphere.

From yesterday's press release:

"The TMT is currently in the final stages of an $80 million design phase. The plan is to initiate construction in 2010 with first light in early 2018. This project is a partnership between the University of California, California Institute of Technology, and ACURA, an organization of Canadian universities. The Gordon and Betty Moore Foundation has provided $50 million for the design phase of the project and has pledged an additional $200 million for the construction of the telescope, and Caltech and the University of California each will seek to raise matching funds of $50 million to bring the construction total to $300 million."

Stay tuned as the best is yet to come.

WorldWide Telescope

2008-05-14T10:48:00.000-07:00

It is an exciting time to be alive if you are interested in astronomy. There is more astronomical images and information available your fingertips than ever before. Adding to this comes yesterday's release of the WorldWide Telescope (WWT) from Microsoft. I haven't had the chance to try it yet, but it should give remarkable images from a wide-range of telescopes based on Earth and in space. Included among those telescopes is Palomar's very own 48-inch Samuel Oschin Telescope.

The 48-inch is a wide-field Schmidt telescope (also called a Schmidt camera) that was built for surveying the sky. Images of the northern sky used in WWT were obtained from the Second Palomar Observatory Sky Survey (aka POSS-II). The pictures for the survey were first recorded on large (14" inches on a side!) glass photographic plates. They were then scanned at the Space Telescope Science Institute in Baltimore, Maryland. From there they were processed and calibrated at Caltech under the leadership of Caltech Professor of Astronomy S. George Djorgovski. This survey has detected over 50 million galaxies and about a billion stars, as well as many other interesting objects.

The WWT also has data from the ongoing Palomar-Quest digital sky survey, also performed with the 48-inch Samuel Oschin Telescope. The glass photographic plates are now long gone, the Palomar-Quest survey makes use of a 161-megapixel camera. Don't forget to read the full press release on Palomar & Caltech's involvement in WWT.

Shown below is one of many infrared images of M81 that you can see on WWT. The image comes from the Spitzer Space Telescope.

Happy Astronomy Day

2008-05-10T10:18:00.000-07:00

Today is Astronomy Day! Lots of places around the country are hold events. In San Diego, the Ruben H. Fleet Science Center will be having a wide-range of events including a live broadcast from Palomar hosted by me.

Here at Palomar we are celebrating by having an engineering run. During the engineering run members of the staff here will make repair and improvements to the telescope's mirror supports, wiring, and dome rails. There's a lot of work going on.

I have been going around taking pictures and yesterday I put together two 3-D shots of the Hale. So if you've got red-blue glasses, put them on and click on the images below.

I'll post more images from the engineering run soon, but don't expect to see them in 3-D.

Oh, for those of you keeping score at home it was on this day 60 years ago that it was announced that the name of the 200-inch telescope would be the Hale Telescope. More on that later.

Asteroid San Diego

2008-05-07T12:35:00.000-07:00

24 years ago this week the City of San Diego was honored for its efforts in helping to control light pollution. The honor came as an asteroid was named "as a celestial tribute to the City of San Diego in appreciation of the city's responsiveness and cooperation in the campaign to restore dark skies of astronomers probing the universe."

We hope that commitment will continue well into the future as new lighting technologies come into use. Preserving dark skies might help us to find any potential dangerous asteroids before they become a threat

Asteroid 3043 San Diego (the streak above) was discovered at Palomar by astronomer Eleanor Helin on September 30, 1982.

Speaking of dark skies, the effort continues in Borrego Springs to make it the next International Dark-Sky Community. Yesterday, Dennis Mammana, was on KPBS radio's These Days speaking about light pollution. You can listen to the archived version of the show here.

Just Hop on the Bus, Gus

2008-05-07T12:15:00.000-07:00

Autoblog Green is reporting that the first natural gas hybrid bus is now running in San Diego. This may be of interest to fans of Palomar Observatory, not just because the bus is green, but because the side of the bus features a mural of 50 attractions in San Diego County. Included in the list is, you guessed it, Palomar Observatory.

An interactive version of the mural is available on line. Be sure to check it out and pass your mouse over Palomar Mountain to see a large view of the dome, complete with spiral galaxy in the sky.

Special thanks go out to Francis French of the San Diego Air & Space Museum to giving me the news.

Shattered Comet

2008-05-06T08:54:00.000-07:00

Two years ago this week Caltech astronomers were using the 200-inch Hale Telescope to observe the fractured Comet 73P/Schwassmann-Wachmann 3 as it came relatively close to Earth.

The comet was discovered by Arnold Schwassmann and Arno Arthur Wachmann in 1930. In 1995 the comet was found to have broken up into four fragments in 1995. By its 2006 passage it had further split into dozens, if not hundreds, of pieces.

The animated gif above shows a sequence of 15 looped images showing the in the foreground against distant stars and galaxies which appear to streak across the frame. Because the comet was moving at a different rate across the sky than the stellar background, the telescope was tracking the comet's motion and not that of the stars. Many fragments of the comet are visible as nearly stationary objects in the movie. In all, 16 new fragments were discovered as a part of the Palomar observations.

In the News . . .

2008-05-02T06:51:00.000-07:00

Here's a sampling of some of the recent media activity associated with the observatory.

We had three documentary film crews here in April. National Geographic Channel's new series Known Universe was here to interview Caltech's Mike Brown. San Diego City College's Newscene was here to do a story on light pollution. A production crew for the History Channel's Modern Marvels was here to do a story on JPL's Near-Earth Asteroid Tracking (NEAT) program & asteroid "crashes".

Here they are filming in the data room for Palomar's 48-inch Samuel Oschin Telescope. Look for the show to air sometime in July.

Yesterday the San Diego Union Tribune newspaper ran a story, Dark skies, bright future, on light pollution and the effort (supported by Palomar Observatory) to make Borrego Springs the next International Dark-Sky Community.

Finally, I just did an interview about the observatory for the Treehuggers International with Tommy Hough radio show. Look for that to most likely air early (5:30 am PDT!) on Mother's Day (May 11) and on their website soon after.

April Skies

2008-04-30T13:55:00.001-07:00

The month of April is nearly done. What have astronomers been looking at with the 200-inch this month? Lots of stuff (as always). Here's a sampling of what they have been studying with the Hale Telescope this month:

Active galactic nuclei
Dust-obscured quasars
Quasar triplets
Optical Transients
Radio Transients
Dust-obscured galaxies
Starburst galaxies
Dwarf galaxies
"A" stars
Cataclysmic variable stars
Intergalactic Medium
Near-Earth asteroids (as they were radar mapped at Goldstone)

Depending on the requirements of the astronomer, the telescope was set up so that observations could be performed with visible light and/or near infrared cameras and/or spectrographs. Our spectrographs and adaptive optics instruments are large enough that they ride in the Cassegrain cage at the bottom of the telescope while our other instruments are up in prime focus.

A few nights were cut short by high humidity, but we lost just two nights due to weather, which isn't bad for April. 2 nights were devoted to engineering on particular instruments.

As is normal, most observers work from sunset to sunrise. The astronomer and the telescope operator work from a warm room. Images are viewed there and analyzed in greater detail after the observing run has been completed. Most astronomers spend much more time pouring over their data than they do in collecting it.

Back Home Again

2008-04-26T11:10:00.000-07:00

Earlier this week I posted about a virtual model of the Hale Telescope. Let me now tell you about a real model.

When I started here there was an old model of the 200-inch telescope & its dome that had fallen on hard times. Look at the 2 pictures below and you'll see what I mean.

The dome was broken in numerous places, part of the inside catwalk had also broken, paint was missing here and the. The entire thing was covered in sawdust.

There are lots of models of the 200-inch telescope in the world, so it would be possible to find or even make another. But this model was built by Russell W. Porter in 1936.

Russell Porter as you may know had a huge role here at Palomar in the early days. He led the surveying team and decided what domes went where. He also figured the optics on the 18" Schmidt, Palomar's first operational telescope. Perhaps Porter's most famous works are the series of detailed cut-away drawings that he did of the 200-inch telescope.

These engineering drawings were made from blue prints, often before the actual parts were assembled. They were detailed enough to show the workers how parts were to fit together. These drawings are magnificent works of art in their own right

Porter's cut-away style is evident in the model, which has been lovingly restored by Robert Kline of Design Dynamics. Bob brought it back last Saturday and I must admit to being overjoyed at seeing the fine work he did.

I think you'll agree that it looks vastly better than the broken-down version above.

America's Next Top Modeler

2008-04-24T08:42:00.000-07:00

Way back in December I posted (Your Own Virtual Hale Telescope) about how Selden Ball has created a wonderful Hale Telescope add-on for the free space simulator program known as Celestia. Selden is doing some mighty fine work and is paying close attention to detail. Finding the answers to some of his questions has taught me some things about the Big Eye.

He continues to work on this virtual Hale Telescope and has created his own blog to show off his progress. Be sure to check it out and you might like his Youtube video as well.

Into the West

2008-04-22T14:49:00.000-07:00

Not much time to write today, but I have been meaning to post this photo for sometime now, so here it is:

This is the view looking into the west arm of the Hale Telescope. To put this into perspective see the next picture. To enter the west arm one needs to walk the gangplank into the hole in the photo below:

Inside the west arm is the slew motor that drives the telescope in declination (north or south). The original 1-Horse Power motor was replaced just a few weeks ago by the Palomar day crew. It will get a little bit of care and be used as a spare, should the new one not last 70 years or so like the first one did.

Defending Your Right to See Starlight

2008-04-19T08:18:00.000-07:00

A year ago I had the privilege to visit the beautiful island of La Palma to attend the Starlight Conference.

Can you pick me out in the crowd?

At the conference the Declaration in Defense of the Night Sky and the Right to Starlight was adopted by the international group of attendees. The basic idea behind it is that everyone should have the right to see and enjoy the night sky and that obtrusive light must be controlled. Why? It is a part of our heritage, nature depends on a 24-hour day/night cycle, our health may depend on it, and of course it is good for astronomy too.

Tomorrow, April 20th has been declared The World Night in Defence of the Starlight. Be sure to visit the link, watch the videos and act to preserve the night sky for everyone.

Flying Electric Trousers

2008-04-12T08:45:00.000-07:00

Yes, Flying Electric Trousers. Years ago astronomers actually rode inside the Hale Telescope all night long. They would sit at the top end of the telescope in what is called Prime Focus. They would be up there to make sure the pointing and tracking were accurate, focus the camera, and physically pull the shutter to start exposing the image.

We have a nice look back at those from the late Jesse Greenstein. He gives two quotes that put things into perspective:

"Working at night in the small cage high above the primary mirror, feeling closer to the stars than the earth, remains an exhilarating and unforgettable experience."

and

"You also had to have a tough bladder because, if possible, if it was a good night, you stayed up from seven o'clock to five. That's ten hours!"

Imagine working high inside the telescope, by yourself, in the dark, for the entire night. Nights on Palomar can be cold, especially in the winter time. That's where the Flying Electric Trousers come into the story.

The trousers and shirt were used to keep the astronomers warm during the night. They were surplus F3-A electrically heated flying suits used by the U.S. Army Air Force during World War II.

Recently a cache of these old suits was uncovered at Palomar. One of the suits is now on display for the observatory's many visitors to see. If you are in the area, come and have a look. The suit on display belonged to Horace W. Babcock, Palomar's director from 1964 - 1978.

A few years ago Jean Mueller, telescope operator (aka Night Assistant) on the 200" managed to save one of the manuals for the old F3-A suits. It is fragile, but it has now been scanned. Here is the cover:

I can post all of the F3-A manual if people are interested in seeing it.

By the way, modern astronomers make use of the Hale Telescope from the comfort of a warm room. A large digital camera rides in Prime Focus. The room features computers for controlling the telescope & cameras, a stereo, coffee, a bathroom and heat. For our smaller telescopes the astronomers do not even need to come to Palomar. They can be operated remotely from the comfort of an office, kitchen or elsewhere.

Time to Get to Work

2008-04-10T16:18:00.000-07:00

I mentioned the epic journey of the 200-inch mirror's trip across the country in my Trainspotting post. Seventy two years ago today, April 10, 1936, the train carrying the giant Pyrex mirror finally pulled into its destination: Caltech in Pasadena, CA.

Under the direction of Marcus Brown, the real work on the glass-grinding and polishing the mirror into a parabola, was set to begin in the Caltech optical shop.

No one knew that the task, with delays for World War II, would span 11 and a half years. In the process some five and a half tons of glass were removed.

I'll have more on Marcus Brown and the figuring of the mirror in a future post.

Clearing the Air

2008-04-05T08:17:00.000-07:00

Ground-based telescopes are entering into a new era with adaptive optics (AO) technology providing sharper views of the universe than ever before. AO allows astronomers to remove the blurring effects of Earth's atmosphere in real time.

The adaptive optics program at Palomar is more than a decade old. In October 2004 we added a new dimension to the program and achieved first light with the laser-guide star (LGS) system. LGS allows astronomers to create an artificial star and use AO in a much larger fraction of the sky.

To do this they shine a narrow sodium laser beam up through the atmosphere. At an altitude of about 60 miles the laser makes a small amount of sodium gas glow. The reflected glow from the glowing gas serves as the artificial guide star for the AO system. The laser beam is too faint to be seen except by observers very close to the telescope, and the guide star it creates is even fainter. It can't be seen with the unaided eye, yet it is bright enough to allow astronomers to make their AO corrections.

The technology is involved. Early on all the time devoted to it is what we call engineering time. Basically that is time on the telescope to tinker, measure and improve all in the name of getting ready for the real astronomical observations that are to follow.

Following that is what is known as shared-risk science. During this time astronomers come to use the LGS system to do real astronomical observations, but with the knowledge that there will still be some time devoted to engineering mixed into the night.

One year ago today was the first night of shared-risk science with Palomar Observatory's laser-guide star adaptive optics program. Caltech professor Lynne Hillenbrand and graduate student Adam Kraus where here to use laser and natural guide Star adaptive optics to conduct a high-resolution imaging survey of young low-mass stars and brown dwarfs in several nearby young associations.

JPL astronomer Patrick Lowrance was back later in the month for another LGS night to study L, T, and brown dwarfs. The time-lapse movie below shows approximately 3 hours of LGS operations during a night as photographed from outside the Hale Telescope dome.

Each frame in the silent movie was a 30-second exposure. Along with the laser, stars and airplanes are visible in the sky.

More photos, movies and information is available on the Palomar Observatory Adaptive Optics page.

Astronomical Bandwidth

2008-04-04T12:57:00.000-07:00

Palomar Observatory just upgraded its data transfer rate from 45 megabits per second to 155Mbps! Data and commands shoot to and from Palomar Mountain via the High Performance Wireless Research and Education Network (HPWREN) enabling new forms of astronomical research that were not possible before.

Studies at Palomar of gamma-ray bursts, near-Earth asteroids, supernovae, Kuiper Belt objects and more have been growing with the use of automated telescopes, armed with big cameras, that have put increased demands on the network. By collaborating with HPWREN and other partners the observatory now has in place what might be the fastest remote astronomical observing capabilities in the universe. Well, maybe just the known universe.

For the full scoop, check out this story from HPWREN news.

Shown above is the crew from HPWREN and Palomar Observatory installing the new microwave antenna outside the dome of the 48-inch Samuel Oschin Telescope.

Touring the Big Eye

2008-04-02T10:16:00.000-07:00

Two years ago yesterday marked the anniversary of the beginning our first program of Saturday tours for the general public. Now that it is April again it is time for the new season of tours to begin.

The tours are available every Saturday (and only on Saturdays) from April through October (except the occasional time when observatory operations may get in the way) at 11:30 a.m. & 1:30 p.m. Tickets are on sale in the Observatory Gift Shop on the day of the tour and are sold on a first-come, first-served basis. The tickets only cost $5 for adult (less for seniors and kids) and in my biased opinion are a fantastic deal.

The tour is a guided hour (often more) that leads up from the visitor center, into the dome for the 200-inch telescope, on to the observing floor and (weather permitting) out onto the outside catwalk. 2 or more docents lead the tour and explain the epic story of how the big telescope was built, how it is used now and what other kinds research is taking place at Palomar.

Visitor response has been overwhelmingly positive with rave reviews and almost all tours selling out. If you get the chance, come join us on a tour.

Pushing the limit

2008-03-29T09:09:00.000-07:00

Rudolph Minkowski, after a long and distinguished career in astronomy, had his last night of observing on Palomar's 200-inch Hale Telescope on March 29, 1960. It proved to be a good night as he measured the distance to the central galaxy in a cluster of galaxies known as 3C295.

With a redshift of 0.46, 3C295 held the record as the most distant known galaxy cluster until 1975. How far away is it? About 4.8 billion light years.

Modern electronic detectors are much more sensitive to light than the old photographic plates used by Minkowski and others and as such galaxies of vastly greater distances are now known making Minkowski's find seem almost close.

Lights Out!

2008-03-28T10:32:00.001-07:00

Be sure to participate in Earth Hour Saturday, March 29. From 8:00 to 9:00 p.m everyone is being asked to turn out their lights for the hour. Why? Turning off unneeded lights will save energy and make a statement towards fighting global warming. Turning off outdoor lights will also give everyone (including those that work at observatories) the opportunity to have a darker sky from which to enjoy (or study) the stars.

March 29th also kicks off National Dark-Sky Week which runs until April 4. This is a great time to see the nighttime sky and learn what can be done to preserve it. Visit the website of the International Dark-Sky Association, THE source on nighttime lighting, to learn about what can be done each and every week of the year.

Catching Up

2008-03-28T10:15:00.000-07:00

Here are a number of Palomar anniversaries that I let slip past me while I was on vacation last week.

March 22, 1955 — Discovery of comet 52P/Harrington-Abell by Robert G. Harrington and George O. Abell on a plate taken during the National Geographic Society-Palomar Observatory Sky Survey.

March 22, 1972 – First light for the Palomar 60-inch telescope located in the Oscar Mayer Building. Thirty six years later the 60-inch is a major workhorse telescope. Its main task now is in rapid-response observations for gamma-ray bursts and other transient phenomena.

March 23, 1993 – Discovery of Comet Shoemaker-Levy 9 at Palomar’s 18-inch Schmidt telescope by Eugene M. Shoemaker, Carolyn S. Shoemaker and David H. Levy. More on this when we "hit" the July anniversary of its impacts with Jupiter.

March 24, 1893 – Walter Baade’s birthday. I'll post some info on Baade later, but in the meantime check out the link or, better yet, read Walter Baade A Life in Astrophysics by Donald E. Osterbrock.

Trainspotting

2008-03-26T13:46:00.000-07:00

Two years and one day after the first (failed) mirror was cast (see yesterday's post) the second (successful) disc began its trip from Corning, New York to Caltech in Pasadena, California on March 26, 1936.

The 20-ton piece of glass traveled 3,000 miles by rail at the breakneck speed of 25 miles per hour. It seemed like all of America came out to watch the event as thousands of people went down to the train tracks, all across the nation, to watch the train roll past. The route was carefully chosen to ensure that all bridges could handle the load and the the crate would safely pass under all of the overpasses along the way.

The train did not travel at night, making layovers in Buffalo, NY; Cleveland, OH; Bellafontaine, OH; Indianapolis, IN; Matoon, IL; St. Louis, MO; Brookfield, MO; Kansas City, MO; Wellington, KS; Canadian, TX; Clovis, NM; Belen, NM; Winslow, AZ; Needles, CA; San Bernardino, CA. It took 16 days to travel from Corning to Pasadena.

With the delays caused by World War II, the mirror remained at Caltech for 11 1/2 years as it was carefully crafted into the proper shape .

A few years ago I had the honor to meet a retired gentleman who was an elementary school student in Kansas when the mirror made its historic trip. He told me how his entire school was brought down to the railroad tracks to watch the mirror and the train go past. It is always a pleasure to meet people who have had a personal connection to part of the Palomar story.

Casting the Giant Mirror - Part I

2008-03-25T13:32:00.000-07:00

I have been on vacation and have missed a few important Palomar dates that I would like to commemorate. I'll have to put them off for a while because today's anniversary is a big one.

Seventy four years ago today (March 25, 1934) the dedicated crew at Corning Glass Works made their first attempt at casting the 200-inch mirror.

Creating the 200-inch mirror was a monumental task.

Initially General Electric was hired to fabricate a 200-inch disc made out of quartz. Nearly a million dollars later, that idea was abandoned. George Ellery Hale approached the Corning Glass Works of New York with a proposal to instead cast the 200-inch mirror out of a special blend of glass called Pyrex. Changes in temperature make Pyrex expand and contract much less than ordinary glass, so a Pyrex mirror would be much less prone to the focus and distortion problems that plagued other glass mirrors.

The top side of a mirror has to be perfectly shaped, while the back is used for support. The back side of the 200-inch disc is honeycombed. The triangular pieces are hollow areas to make the mirror weigh less, while the round area are places where the mirror is supported from below to help the topside to maintain its critical shape. Making the honeycomb undersurface provided some challenges.

A mold was built inside of an oven (think bottom of a waffle iron) to give the mirror’s underside its special shape. The hollow spots were created by bricks that were held down by steel bolts.

After taking nearly a month to melt enough glass, on March 25, 1934 the molten glass was ladled into the mold. Alas, the glass was hot enough to melt the steel bolts and the bricks floated to the surface and ruined the mirror. This first disc is on display at the Corning Museum of Glass in New York. The successful second casting was performed in December 1934.

The Corning Museum of Glass website has a great article on the making of the mirror called The Glass Giant.

I have seen many wonderful photographs of March & December, 1934 castings. Thankfully it was also captured in two paintings by artist Christian Jacob Walter. Shown above is "Pouring Glass". The other painting is called "Ladling Glass." The paintings are on display at the Earth and Mineral Sciences Museum at Penn State University.

Later this year I hope to make the trek to visit Corning and to see the first disc. It is a part of the Palomar heritage that I need to visit.

Five Years and Counting

2008-03-17T15:13:00.000-07:00

As of today I have been at Caltech's Palomar Observatory for five years. It continues to be a pleasure and an honor to work at this fine institution with its remarkable, dedicated staff. The observatory has a distinguished history and a promising future of exploration and I am happy to be able to help bring the Palomar story to many people.

Helping me to bring Palomar to the people are a great group of volunteers, the Palomar Observatory Docents (or PODs as I call them). Many of our active docents are shown in this recent group photo.

The PODs are a dedicated and wonderful group of people who have become part of the Palomar family by helping in our public outreach program in a variety of ways, including giving tours of the Hale Telescope.

We are always looking for more people who might be interested in helping out, especially as we are about to enter into our new tour season with docent-led tours of the 200-inch Hale Telescope given twice daily on Saturdays (11:30 am & 1:30 pm) from April through October.

Potential docents don't need to be an astronomer or a Palomar expert to apply. A willingness to learn and an interest in speaking to people is all that is needed. More information can be found here.