The Remarkable Fresnel Lens

Fresnel Lens, Vashon Island, WA, 5th Order

A modern invention of the 1820s that revolutionized the science of light and shipping was the Fresnel lens. This invention, created by Augustin-Jean Fresnel (1788-1827), is a lens with an array of prisms capturing light and extending its reach. Today we are still influenced by these lenses around the world.

 

Fresnel (pronounced fray-NEL) lenses were originally created as a solution for the tragic ship wrecks that were prevalent in the 1800s. Ship captains, sometimes unable to see coastal waters due to low light, crashed their vessels into the reef with disastrous results.

 

Light naturally diffuses in all directions. Finding a way to cut down on this diffusion was the challenge for many years. At the time, shiny metal reflectors around the light source (oil lamps) were used to enhance the light, but this only gave about 50% reflection.

 

French physicist Augustin Fresnel’s skill and brilliance in interpreting the mechanics of light led to innovative lens inventions. Lighthouse visibility improved tremendously, and consequently made shipping safer.

 

Although I have been to many lighthouses, I never regarded the light as anything special. Then last year I was in the Visitor Center at a California State Park, Angel Island, and became instantly dazzled by a waist-high glass piece mounted on the floor. It had once been used in the lighthouse on Angel Island, and was on display.

 

It captured the light of the room in the most extraordinary, and beautiful, way. I’ve been a fan ever since.

 

Vashon Island, WA Lighthouse. You can see the Fresnel lens in the tower through the windows.

There are numerous aspects that make the Fresnel lens unique and effective:

• the beehive-shaped design to capture multiple levels of light
• it is constructed with concentric grooves that act as individual refracting surfaces.
• the center is shaped like a magnifying glass, concentrating the beam

 

The first lens was installed in 1823 off the west coast of Fresnel’s home country, France, near Brittany, a land long-known for its rugged coasts. Here there were treacherous reefs that tragically and repeatedly snagged and destroyed ships. The new lens was a success.

 

Thereafter the French coast was lit up by Fresnel lenses. More info: Cordouan Lighthouse.

 

Early innovations began in France and Scotland, with America and other countries following. Chronology of Fresnel Lens Development.

 

Fresnel lens, Vashon Island, WA. Mt. Rainier in distance

Each lens was produced in brass-framed sections and could be shipped unassembled from the factory.

 

They were made in six different classifications, or orders. A 1st order lens is the largest size, at approximately 12 feet high (3.7 m), lengthening the light beam 26 miles.

 

Wikipedia Fresnel Lens

 

Here is a cross section of the Fresnel lens (on left) compared to a conventional lens of equivalent power (on right).

Courtesy Wikipedia

 

Article:  “The Fresnel Lens” written by Thomas Tag

 

Fresnel Lens classifications. Courtesy partsolutions.com

 

Lighthouse beacons have been  significantly modernized since the 1800s, but there are still lighthouses with Fresnel lenses–some in working order, some just on display. There are also many Fresnel light-refracting techniques in use today: spotlights, floodlights, railroad and traffic signals, camera and projector lenses and screens, and emergency vehicle lights.

 

List of U.S. lighthouses with Fresnel lenses

 

Many photographers and artists, including myself, hold a deep fascination and reverence for the miracle of light. How fortunate for us to have had Fresnel’s engineering skills to brighten this further.

 

Written by Jet Eliot.
Photo credit: Athena Alexander unless otherwise specified.

 

Rotating Fresnel lens, 1st order, dated 1870, displayed at the Musée national de la Marine, Paris. Courtesy Wikipedia.

 

1st Order Fresnel lens, Cape Meares Lighthouse, Tillamook, OR, USA. Courtesy Wikipedia.

 

 

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Northern California 2017 Fires — One Year Later

A calm June day, 8 months after the fire

One year after the October 2017 Northern California Wildfires, we celebrate our recovery. Next week is the anniversary, October 9th. Here are a few photos of our rebuilding stages, our house that was dead center in the middle of it all.

 

For all but two weeks of this past year we did not live at home, because we had no electricity or water. We lived instead in vacation rentals and apartments, sometimes a friends’ house or rental unit–eight different places, four different counties. With 90,000 evacuees, there was a housing shortage.

 

Every week we filled the bird feeders and refreshed their water trays

We visited our house frequently, met with the contractor and sub-contractors, and tended to the physical repairs. Filled the bird feeders. The house had not been consumed by the fires; just damaged. We lost our storage building filled with clothes, tools, and keepsakes; a guest cottage, and the forest.

 

With 8,900 structures lost in the firestorms, repair work was slow, and often shoddy.

 

Chainsaws and chippers are a common sight.

Rebuilding the back yard

 

People suffer all the time–earthquakes, hurricanes, floods, school shootings, cancer, war, assault. Some of it from natural disasters, some of it from hateful activity.

 

In the midst of the chaos and disaster in this past year, what I found was far more love than hate.

With our next door neighbors on the first day back

 

Rebuilding the new well, 9 mos. after the fire. An excellent team.

 

Our forest

 

Sometimes the gifts were obvious, like a friend buying us dinner, or letting us stay in their home, or family coming across the country to help. Other times the gifts were less obvious, like a simple smile, or someone just listening to my aching heart. Phone calls, emails, texts, cards, packages, songs, meals. So many WordPress friends who sent messages, remembered, extended kindness.

 

People ask, what do I need to know about insuring my home in case this ever happens to me? There are many answers I can give. Inventories, tasks, insurance policies. But what is the real answer, what do we really need to recover from something like this?

 

Love and kindness.

 

 

But what about when the insurance adjustor was unreasonable and hammering, what then? She lied, she denied, she fought, made “mistakes” in their favor to the tune of $45,000.00. Do I give her love and kindness?

 

No. In that case, I gave myself love and kindness–usually by going to a movie, or reading, sometimes the French bakery. Sometimes I just laid down and cried. My partner and I, my wife, we walked a lot, walked in the winter fog and counted cormorants.

Cormorants, Tiburon

Today is a windy day, and it’s the first week in a year that I am back at my own desk. The dead trees outside my window, I notice for the first time, don’t bend and sway in the wind. They are stiff, and rattle. A raven rides the thermals. A finch landed in a dead tree, apparently content with stiffness.

 

We all go on. The lucky ones, the survivors, we go on. We learn, we suffer, we hope.

 

And we give a hand, or lend an ear, and we help each other.

 

What have I really learned? Not to ever underestimate the power of love and kindness.

 

Written by Jet Eliot.

Photos by Athena Alexander.

Parrolets, Mexico

 

Raptors in Autumn

Barred Owl, Texas

Every fall thousands and thousands of raptors in North America migrate south for the winter as their food supplies begin to wane. Here are some basic facts about raptors and where to find them as we enter into the northern hemisphere’s autumn.

 

Also known as birds of prey, raptors include many different species. Some more commonly known raptors are: eagles, ospreys, kites, hawks, vultures, falcons, and owls.

Osprey in Mangroves

Not all raptors migrate. It depends on how cold the winters get, if there is enough available prey. We are fortunate in Northern California to see many raptor species in all seasons.

 

Other parts of the country, however, have consistently cold winter weather and, consequently, raptor migration every autumn.

 

Snail Kite

 

Although raptor migration lasts roughly between August and November, late September is the prime time for watching these grand birds.

 

Bald Eagle, California. This raptor almost went extinct.

With their sturdy wings and broad wing-spans, they utilize upward air currents, i.e. thermals, to assist with their long flights. The migrating populations concentrate along mountain ridge lines, coast lines, and other topographical features to take advantage of the updrafts.

 

See the map below for raptor migration pathways in North America.

Merlin, Sacramento NWR, California

American Kestrel, California

Turkey vulture pair on fence, drying wings; Calif. coast

 

There are numerous predictable spots for hawkwatching in North America, where anyone can observe migrating raptors, especially hawks.

 

Two popular U.S. hawkwatch stations I have visited are Cape May, NJ on the east coast; and Hawk Hill outside San Francisco on the west coast. Hawk Mountain in Pennsylvania is the most famous hawkwatch station in the U.S.

Red-tailed Hawk in rain, California

 

Cooper’s Hawk, California

 

Because migrating hawks fly high over land masses, the birds are usually far away from us ground-dwellers. Raptor migration birding, therefore, engages in a different kind of bird-observing technique. There are no bird sounds or calls, and no close-up views for bird identification. Instead, birders systematically scan the sky with binoculars or scopes; and identify the species by silhouette, profile, size, plumage, and flight behavior.

 

Many times I have stood beside hawkwatchers with my own high-powered binoculars looking at what they look at, as they call out their sightings. Usually, to the bare eye, the hawk is the size of a rice grain.

 

Data is recorded and posted daily. The information gleaned from it is paramount in raptor conservation.

 

Osprey, Florida

 

Red-tailed hawk with chick, California

 

California Condor, Calif. — another raptor we almost lost to extinction

 

Great Horned Owlet, California

 

Raptors are important birds for providing our planet with a healthy ecosystem.

 

Raptor Conservation Wikipedia

 

If you are interested in finding a Hawkwatch venue in North America, hawkcount.org provides links to approximately one hundred sites.

 

For folks who just enjoy seeing a powerful bird soaring overhead, now is a good time of year to keep your eyes open and your neck craned.

 

Written by Jet Eliot

Photos by Athena Alexander, all North American raptors

PS – For my friends–you’ll be happy to know Athena and I are moving  home tomorrow, after 11.5 months displacement following the October 2017 Wine Country fires. This is our ninth and final move in the post-fire event. Our own migration.

 

North American Raptor Migration Pathways. Courtesy hawkmountain.org

 

Cable Cars – A San Francisco Treat

Hyde-Powell Cable Car track

Beneath the streets of San Francisco are underground cables that run all day long. If you can catch a quiet moment on one of the cable car streets, you will hear the high-pitched hum of the constantly running cable.

 

Originally invented by Andrew Smith Hallidie, cable cars have been carrying commuters and tourists through San Francisco since 1873. Designated a U.S. National Historic Landmark, it is the only true cable car system left in the world.

San Francisco cable car, California Line

Cable Car Wikipedia

 

This network of cables and pulleys originates from one powerhouse located at Washington and Jackson Streets, and it runs the whole city’s cable car system. Here there is also the Cable Car Museum, which I recommend; it’s free.

Cable Car Museum. Underground cables operating in powerhouse

Each cable car has two operators: the conductor, who takes tickets ($7.00); and the grip person, who runs the car and grips the brakes.

 

With the underground cable running, the grip person starts and stops the cable car by attaching to or releasing from the cable. This takes great strength; the car has a passenger capacity of 60-68 people. So one Herculean person operates the grip that brakes the car carrying 60+ people.

 

Cable car grip man

 

 

Cable car stop

 

San Francisco Hyde Street cable car

The history and facts are interesting…but it’s the ride that is the thrill.

 

I have lived in or around San Francisco for 30 years, and I never ever tire of riding the cable cars.

San Francisco cable car

The wind is blowing through your hair, the car is rocking slightly, and creaking. The car is sandwiched between UPS delivery trucks, other double-parked work trucks, and speedy cars as we trundle up and down the precipitous hills.

 

Street scenes abound as we cruise by apartment buildings, houses, corner stores, and schools.

 

The clanking of the bell, the dampness of the fog.

 

From a few of the hilltops you can see Alcatraz Island in the distance, anchored in the Bay; and the Golden Gate Bridge. The aroma of savory foods waft out of Chinatown.

 

A quintessential San Francisco experience…not to be missed.

 

Written by Jet Eliot.

Photos by Athena Alexander.

Cable car riders. From R Athena, Jet, Jet’s sister, and brother-in-law. July 2018.

Check out this old cable car commercial from 1962, pretty fun.

 

Monkeying Around

Guatemalan Black Howler Monkey, Belize

Monkeys  and humans are both primates — I think that’s why humans find monkeys so entertaining to watch. There are 260 species of monkeys currently living in the world, here are a few monkey species I have seen in the wild.

 

Wikipedia Monkey

 

Monkeys are generally divided into two major types: Old World and New World.

 

The Old World monkeys photographed here were seen in different parts of Africa. They are also found in Asia.

Olive Baboon, Tanzania

Baboons are one of the easier Old World monkeys to spot not only because of their larger size, but also because they travel in large troops. There were many instances when the safari vehicle rounded a corner to find a troop of 50 or 100 baboons walking their daily route.

Olive Baboon, Tanzania, Africa

Monkeys grooming one another is a frequent occurrence; it is one of my favorite monkey observations. Known as social grooming, it is done for health benefits as well as relationship bonding.

Savannah Baboons grooming, Botswana

 

Typical of monkeys, the vervet monkeys have extensive hierarchies and elaborate social behavior.

Vervet Monkey, Botswana

Vervets have been known to express 30 different alarm calls. They can readily be observed vocalizing warnings to their peers when a predator is nearby. Vervets take this vocalization to a higher level of intelligence by specifically saying which of their four predators is lurking.

 

Our guides could tell us what predator we were about to see based on the different vocalizations they recognized in the vervet monkeys’ alarm calls.

 

Native to Africa, black-and-white colobus monkeys are strikingly beautiful to see dancing among the treetops.

Colobus Monkey, Mt. Kenya, Africa

Blue monkeys, though they’re not really blue, mostly eat fruit and can be found in Central and East Africa.

Blue Monkey, Lake Manyara, Tanzania, Africa

 

Now let’s head to the Western Hemisphere. New World monkeys, found in Central and South America, include the capuchin and howler monkeys.

 

There are approximately ten different kinds of capuchin monkeys, sporting many different colors. They are considered the most intelligent of the New World monkeys. Energetic and lithe, they have been used as service animals to assist people challenged with spinal injuries.

Brown Capuchin Monkeys, Peru

 

Known for their eerie, howling calls, howler monkeys are considered to be the loudest land animal. It is one of my favorite sounds in the rainforest…except for my first time when I thought I was going to die.

Red Howler Monkeys, Peru

Here’s a You Tube video with a good howler recording. Click here. 

Red howler Monkeys, Manu, Peru. Photo by Bill Page

 

It is an expansive family of interesting beings, our fellow primates, the monkeys.

 

Written by Jet Eliot.

Photo credit: Athena Alexander unless otherwise specified.

Blue Monkey, Mt. Kenya, Kenya, Africa

 

Curious George

 

Sharing the Wrens

Bewick’s Wren on grape vine, California

A perky bird with a tiny body and big sound, wrens can be found around the world. The dominant wren family, Troglodytidae, is primarily found in the New World, as well as Europe and Asia. There are 88 species in this family.

 

One came visiting in the garden the other day to remind me wrens are present in cities, towns, and gardens as well as forests, canyons, deserts, marshes, and other rural areas. There are grape vines in the urban garden where I am currently residing, and this wren, above, comes to visit every day.

 

Wren overview, Wikipedia

 

Preying on insects and spiders, they dart and dash in search of a meal in a variety of habitats. The array of habitats is impressive, and often a wren is named after the habitat it prefers. There are marsh wrens, rock wrens, canyon wrens, cactus wrens, and more.

 

Intricately marked and often sporting a cocked tail, the Troglodytidae wren is small, averaging 5.5 inches (14 cm).

 

Horicon Marsh, Wisconsin. Typical setting for marsh wrens

 

Marsh Wren, Horicon Marsh, Wisconsin

Lately, as we enter into autumn in the northern hemisphere, I hear their scolding calls. In springtime we are greeted by wrens with a more melodious breeding song.

 

North America has approximately 11 different wren species. The three wren species I see most in California: the ubiquitous house wren, seen in towns, suburbs, and rural areas; the marsh wren, in marsh areas; and the Bewick’s wren, seen throughout the western U.S.

House Wren, Wisconsin meadow

While it is always fun to chase after my familiar hometown wren friends, spotting other wren species in travel is equally as enjoyable.

Canyon Wren in a Nevada canyon

The canyon wren’s song is always a thrill, with their distinctive descending notes echoing throughout rock canyons. Allow me to share their song with you: click here and hit the red arrow.

Carolina Wren, Texas; parent going to the nest

When I spot a Carolina wren, I am never in the Carolinas. When I spot a house wren, I am never in a house. But when I spot a marsh wren, I am always at a marsh.

 

Wherever I am, they are a joy.

 

Written by Jet Eliot

Photos by Athena Alexander

 

House wren going to the nest (under rusty globe)

 

Rock Wren drawing by John James Audubon

 

Happy Solstice

Monarch Butterfly, Horicon Marsh, WI

Those of us in the northern hemisphere are entering into summer solstice this week, celebrating the longest day of the year and the beginning of summer. The word solstice derives from the Latin for sun (sol) and to stand still (sistere).

 

Here are a few North American summer moments, when the power of the sun (and the camera) slowed the natural world down to a perfect stand-still.

Mother Moose and calf, Rocky Mtn. Nat’l. Park, Colorado

 

 

Common Green Darner, Anax junius. California

It’s a quiet moment when dragonflies cruise by–nothing says summer days like a dragonfly.

Halloween Pennant Dragonfly, Wisconsin

 

Insects and wildflowers grace us with color and vibrance as they busily gather sustenance during these longest of days.

Hypericum coccinum, aka Gold Wire, with ladybug. California

 

Great Spangled Fritillary (female), Wyoming

And is there a more remarkable insect than the butterfly? I don’t think so.

 

The miracle of life in four distinct stages. They start out the warm season as an egg, hatch into a tiny caterpillar, then forage their way across the host plant, a legacy from their mother.

 

As they continue to eat, they grow into plump caterpillars until they sense the time for pupation, and form their own protective chrysalis. Then one day they stretch out of the chrysalis, unfurl wings, and fly off.

 

Anise Swallowtail caterpillar, California

 

Anise Swallowtail Butterfly, California

 

Another summer gift for us to behold: birds fledging from their nests, launching into their first flights.

Pacific-slope Flycatcher nestlings, 15 days of life. They fledged soon after.

 

Carolina Wren, Texas; parent tending the nest

 

Summer is a time for singing, and no birds enchant us more with melodious sweetness than the songbirds.

Prairie Dickcissel, Attwater Preserve, Texas

 

Common Yellowthroat, Horicon Marsh, Wisconsin

 

Rivers and ponds, forests and prairies, suburbs, cities and countrysides all come alive in summer.

Marsh meadow, Horicon Marsh, Wisconsin

Ft. Collins park, Colorado

We humans are cradled by the sun, presented with a whirlwind of nature during these long and productive days. We, too, sing and flutter, grow and frolic.

 

Written by Jet Eliot

Photos by Athena Alexander

I am taking a short summer break, my friends, will return in a few weeks. I hope your days, whether they’re going into summer or winter, are filled with beautiful moments.

Twelve-spotted Skimmer Dragonfly, California