Archive for March, 2011

Light Snow on Cherry Blossoms

March 27, 2011


One week after the March Equinox, sometimes called the Spring Equinox (in the Northern Hemisphere), it snowed in Washington, D.C. Although snow in late March is unusual in Washington, D.C., the latest measurable snowfall was recorded on 28 April 1898.

I went for a short photowalk to photograph snow on the cherry blossoms in the community where I live: light snow was falling when the photowalk began; the sky was clearing rapidly when the photowalk ended. According to the National Park Service, cherry blossoms around the Tidal Basin will peak on Tuesday, 29 March 2011.

Duck, duck, goose!

March 24, 2011


A few shots from a short photowalk through Huntley Meadows Park. I visited the park to scout a location for my “Equinox sunrise” photo shoot. Along the way, I saw ducks, geese, a new beaver lodge, and frog eggs. (It’s mating season, you know.)

Photo Captions:

  1. Ducks (the male has a blue-green head).
  2. Canadian Geese.
  3. Geese.
  4. Beaver lodge.
  5. Frog eggs (see round blobs in the water, above the shadow of my head).
  6. Frog eggs.


Equinox sunrise

March 21, 2011


I visited Huntley Meadows Park to photograph sunrise on the March Equinox, 20 March 2011. I used Theodolite Pro app to record a time series of geotagged screen captures beginning at 7:12 a.m., the official time of sunrise in Washington, D.C. on March 20th. On the equinoxes, the Sun rises due east (90 degrees azimuth) and sets due west (270 degrees azimuth). Looking at photo 1 of 6, notice that the camera is facing due east (090°) and the disk of the Sun is below the tree line at 7:12 a.m.; by the time the Sun is clearly visible at 7:28 a.m. (photo 5 of 6), the Sun had moved along its path across the sky to a point slightly south of east (see Editor’s Note, below).


I used Pro HDR app to shoot a composite image (shown above) of the scene looking eastward across the wetland. Notice there is some ghosting visible along the tree line, probably due to the fact that I was too cold to stay still for a handheld shot!

Related Resources:

Editor’s Note: Sunrise is defined as the time of day when the Sun’s upper limb appears above the true horizon. From my viewpoint at Huntley Meadows Park, the true horizon was obscured by the visible horizon (the tree line). Therefore, I was unable to see the Sun‘s disk on March 20th at exactly 7:12 a.m.

Planet Earth is a magnificent timepiece! The Earth rotates counterclockwise once every 24 hours. One complete rotation equals 360 degrees. The rate of the Earth’s rotation equals 15 degrees per hour:

360°/24 hr = 15°/hr or 15°/60 min, which reduces to 1°/4 min

Notice that the first five photos were taken approximately four (4) minutes apart; photo 6 of 6 was taken two (2) minutes after photo 5 of 6. Therefore, 18 minutes elapsed between the first and last photos. That means the Earth rotated 4.5 degrees during the photo shoot. Do the math:

18 min/1 x 1°/4 min = 4.5°

Now we know the Sun’s azimuth was 94.5 degrees when photo 6 of 6 was taken. No wonder it appears as though the Sun didn’t rise due east on the Equinox!

Diptychs of Diptych Sundials

March 18, 2011



Like “Drawing Hands,” the lithograph by M. C. Escher featuring one hand drawing another, I thought it would be interesting to create diptych photo collages using images of diptych sundials. Since I don’t have access to a collection of diptych sundials, I decided to take advantage of the laws related to intellectual property that allow liberal use of copyrighted materials for educational purposes: I repurposed several photos of diptych sundials from the National Maritime Museum for a mini-lesson on diptychs and diptych sundials. The diptychs (shown above) were created using Diptic app.


According to the Apple OS X “Dictionary” widget, a diptych is:

  1. a painting, esp. an altarpiece, on two hinged wooden panels that may be closed like a book.
  2. an ancient writing tablet consisting of two hinged leaves with waxed inner sides.

The British Sundial Society Glossary definition of a diptych sundial is as follows:

a portable (pocket) dial in which a vertical and horizontal dial are hinged together, and a common cord gnomon running between them also ensures that they open to a right angle [90 degrees]. [Diptych sundials are] latitude specific.

Related Resources:

Editor’s Note: I currently serve as chairperson of the North American Sundial Society (NASS) Education Committee. Educators interested in exploring ways to use sundials to enhance and/or enrich classroom instruction are encouraged to contact me.

Butterflies are beautiful …

March 17, 2011


but I must admit I’ll never look at butterflies the same way as I did before this experience! An Eastern tiger swallowtail butterfly (Papilio glaucus) eating animal excrement, possibly raccoon droppings. This individual is a female, as indicated by “the bluish postmedian area on the ventral hind wing [with] one row of orange spots.” The photo was taken during a photowalk at Huntley Meadows Park.

Monarchs Mating

March 16, 2011

During a photowalk through the Children’s Garden at Hollin Meadows Science and Math Focus School, I observed two Monarch butterflies mating. Now that’s something you don’t see everyday! I used my Apple iPhone 3GS to shoot some still photos and video clips, some of which turned out remarkably well (he said, not too modestly). During post-processing of the media, I used VLC media player to capture a couple of video snapshots, including an annotated snapshot that highlights the “androconium” (one of two “hindwing pouches” on the male butterfly’s lower wings).

Asclepias (all species), commonly known as “Milkweed,” is the “host plant” for Monarch butterflies. See a photo index of more pictures of Monarch butterfly caterpillars and Milkweed plants.

Photo Captions:

  1. Monarch butterfly (male) feeding on Scarlet Milkweed.
  2. Video snapshot.
  3. Annotated video snapshot, highlighting androconium (circled in red).
  4. Several Monarch butterfly caterpillars feeding on Milkweed.
  5. Monarch butterfly chrysalis casing, shown upper-right.

Related Resources:

Photowalking Mount Vernon Farmers Market

March 15, 2011


Mount Vernon Farmer’s Market — located in the parking lot of Fairfax County Sherwood Regional Public Library — is open Tuesdays from 8:00 a.m. to 12:00 noon, May through November.

I used PicPosterous app to upload the photo gallery, shown above. PicPosterous app predates the Posterous Mobile apps (for iPhone and Android), and is showing its age! PicPosterous app enables you to upload one photo at a time to a Posterous gallery; you can add more photos to the same gallery, but again, you select photos one at a time. You can add a title and narrative text to the gallery; you cannot add tags. The user interface is very clunky and counterintuitive, in contrast with the Posterous app. Bottom line: PicPosterous app’s time has come and gone; move on to Posterous app and never look back!

ColorBlast! from the past

March 14, 2011


A self-portrait taken in the classroom where I taught Physical Science. The original photo was taken using an Hewlett Packard HP Photosmart R740 digital camera and edited using ColorBlast! Lite app, the free version of ColorBlast! app. The dimensions of the original photo are 1,024×768 pixels (Photo 3 of 3); the edited version is 640×480 pixels (Photo 1 of 3). Photo 2 of 3 is a screen capture from my iPhone 3GS (480×320 pixels), showing a Facebook status update that featured the edited photo.

Freezing rain event diptych

March 13, 2011


I went for a short photowalk to photograph a freezing rain event that occurred overnight January 17-18, 2011 in the Washington, D.C. metropolitan region. The diptych (shown above) was created using Diptic app.

Related Resources:

Milway Meadows panorama

March 12, 2011


A 16-image panorama at the intersection of Milway Drive and Woodlawn Trail in the community of Milway Meadows, Fairfax County, VA. Photo created using AutoStitch Panorama app.

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