Posts Tagged ‘education’

Diptics: Henry Moore Sundial Sculpture

January 23, 2012

The following gallery of four-panel diptychs features several photos of the Henry Moore Sundial Sculpture, Sundial Plaza, Adler Planetarium & Astronomy Museum, Chicago, Illinois USA. The sculpture is a type of sundial that is sometimes referred to as a “bowstring” equatorial sundial. See also an annotated photo of the sculpture that illustrates how a “bowstring” equatorial sundial is simply a reduced model of the Earth.


Tech Tips: The preceding composite images were created using Apple “Aperture,” Adobe “Photoshop,” and “Diptic” app for Apple iOS mobile devices. For details, see “Advanced technique for creating Diptic ‘photo tiles’” (one of my recent Posterous posts). The border is five (5) pixels wide, rather than my usual preference of 10 pixels.

Copyright © 2012 Walter Sanford. All rights reserved.

Diptics: University of Colorado Boulder

January 21, 2012

For more than a decade, I was actively involved with several K-13 education outreach initiatives of the American Meteorological Society. I was fortunate to be able to visit Boulder, Colorado USA for several in-service training workshops for science teachers. We stayed at Kittredge Complex, University of Colorado, for every workshop.

The following gallery of three-panel diptychs features several photos of the University of Colorado Boulder campus. Shown clockwise from the top: Kittredge Complex, with a spectacular view of the Flatirons in the background (part of the Front Range of the Rocky Mountains); the John Garrey Tippit Memorial Sundial, an equatorial sundial; and the Colorado Scale Model Solar System (notice my reflection and the Fiske Planetarium and Science Center behind me).


Tech Tips: The preceding composite images were created using Apple “Aperture,” Adobe “Photoshop,” and “Diptic” app for Apple iOS mobile devices. For details, see “Advanced technique for creating Diptic ‘photo tiles’” (one of my recent Posterous posts). The border of Photos 1 and 3 is five (5) pixels; 10 pixels for Photos 2 and 4.

Copyright © 2012 Walter Sanford. All rights reserved.

Sundial at Christ Church, Alexandria, VA USA

January 15, 2012

A horizontal sundial is located on the grounds of historic Christ Church in Old Town Alexandria, Virginia USA. The North American Sundial Society Dial Registry listing says, the “dial appears to have been designed for 32 degrees N.” In order to determine whether the sundial is in fact aligned properly, I examined a couple of photos that were geotagged by my Apple iPhone 4. (See “Tech Tips” for details, below.)

Similar to setting the correct time on an analog clock or wristwatch (by moving the hands of the timepiece into proper position), properly orienting a horizontal sundial will move the shadow of the gnomon (or style) into position so that the dial face displays the correct time.

  1. The dial plate should be horizontal.
  2. The shadow-casting edge of the gnomon should be parallel to the Earth’s axis, inclined at an angle equal to the latitude of the sundial.
  3. The tip of the gnomon should point toward the North Celestial Pole (i.e., Polaris, the North Star). More simply, the dial face should be aligned so that 12 noon points toward geographic north and the 12 noon hour line is aligned with your local meridian.

Photos 1-2 of 8 (shown below) verify that the dial plate is horizontal. Photos 3-4 show the gnomon is inclined at an angle of 31.86 degrees (~32 degrees); Photos 5-6 show the latitude of the sundial is 38 degrees 48 minutes 22.2 seconds. Photos 7-8 show the image direction is 218.4602 degrees, meaning the tip of the gnomon is pointing southwest rather than true geographic north (0, 360 degrees).


Bottom line: The Christ Church sundial appears to have been made for another location and is aligned improperly for its new location. In other words, the sundial is strictly ornamental and will not tell time correctly.

Tech Tips: The iPhone Camera app works seamlessly with two built-in devices to geotag photos: the GPS sensor measures position on Earth; the digital compass measures “image direction.” PixelStick, an application for Mac OS X, was used to measure angles in one of the photos (see Photos 1-4, above). Apple “Preview” was used to display GPS info for both photos (see Photos 5-8, above).

Photos © Copyright 2012 Walter Sanford. All rights reserved.

Diptics: Freezing rain event

December 29, 2011

I went for a short photowalk to photograph a freezing rain event that occurred overnight January 17-18, 2011, in Alexandria, Virginia USA. The following three- and four-panel diptychs were created using Apple Aperture and Diptic app for Apple iOS mobile devices.


Here is a link to 18JAN2011_freezing-rain, one of my Google Picasa Web Albums, featuring all of the photos I shot soon after the weather event ended.

Teacher Tips: What is freezing rain? For a graphic explanation, see “How winter storms bring rain, ice and snow,” an interactive online article from the USA TODAY Weather Book by meteorologist Jack Williams. See also, “Snowflakes – A Thematic Approach (A Flurry of Interdisciplinary Ideas for Teachers)” perfect for enriching/extending everyday instruction during the winter season.

Photos © Copyright 2011 Walter Sanford. All rights reserved.

Lamb’s Ear

November 14, 2011


Lamb’s Ear (Stachys byzantina), an unusual flowering plant spotted during a photowalk through the Children’s Garden, Hollin Meadows Science and Math Focus School. Lamb’s Ear seems to be very attractive to Bumble bees (Bombus sp.) and Small Cabbage White butterflies (Pieris sp.), among other pollinators.

Related Resources:

Photos © Copyright 2011 Walter Sanford. All rights reserved.

Frozen dew — it’s just a phase I’m going through!

November 4, 2011


I observed frozen dew on the outside of the windshield of my 2007 Honda Civic four-door sedan, at ~8:30 a.m. on Wednesday, 02 November 2011. There was dew (liquid) on the driver’s side door. In fact, I remember my hand got wet when I opened the car door. I thought the windshield had dew on it, that is, until I turned on the windshield wipers … surprise, the windshield was covered with ice (solid)! In the preceding photo gallery (shown above), you can see frozen water droplets as well as rivulets where liquid water had been flowing down the windshield before freezing solid.

What is frozen dew? The National Weather Service Glossary defines “frozen dew” as follows:

When liquid dew changes into tiny beads of ice. This occurs when dew forms and temperatures later drop below freezing.

First, dew formed when the air temperature reached the dew point temperature and water vapor (gas) in the atmosphere condensed to become dew (liquid). Next, some surfaces (e.g., my automobile windshield) reached a temperature below the freezing point temperature of water substance (0°C, 32°F). Finally, the dew froze into ice (solid). Voila, frozen dew! Frozen dew occurs only a few times a year, usually during spring and fall.

Is frost the same as frozen dew? In a word, no! Remember, frost NEVER exists in the liquid phase — frost forms when water vapor (gas) changes phase to ice (solid) in a process called deposition.

In-Depth Analysis

The following data table shows select weather observations at Ronald Reagan Washington National Airport (DCA) on Wednesday, 02 November 2011. (Note: All temperatures expressed in Fahrenheit degrees. Dew Point Depression = Temperature – Dew Point Temperature. Weather data provided courtesy Brandon Peloquin, Senior Forecaster, National Weather Service Baltimore/Washington Forecast Office, Sterling, Virginia.)

Time (UTC) Time (EDT) Temperature Dew Point Temperature Dew Point Depression
04:00 12 midnight 46 42 4
05:00 1:00 a.m. 45 41 4
06:00 2:00 a.m. 43 40 3
07:00 3:00 a.m. N/A N/A N/A
08:00 4:00 a.m. 43 39 4
09:00 5:00 a.m. 42 39 3
10:00 6:00 a.m. 42 38 4
11:00 7:00 a.m. 42 38 4
12:00 8:00 a.m. 42 38 4

Notice that the temperature never was equal to or lower than the dew point temperature at any time overnight. Further, the temperature never was below the freezing point temperature. Nonetheless, dew formed on some surfaces of my car and frozen dew formed on other surfaces. A rule of thumb commonly used by meteorologists says that condensation and/or deposition may occur when the dew point depression is either equal to or less than five (5) Fahrenheit degrees, due to radiative cooling on cloudless nights (like Tuesday night/Wednesday morning).

Related Resource:Freezing Rain Event,” (a post on my WordPress blog) featuring a few more photos of my car covered in ice that formed by a different type of physical change.

California coneflower

October 26, 2011


California coneflowers (Rudbeckia californica), a species of flowering plant in the aster family, spotted during a photowalk through the Children’s Garden, Hollin Meadows Science and Math Focus School.

Tech Tips: Photos 1 and 2 (of 3) were cropped using Apple “Aperture,” a professional-grade tool for organizing and adjusting photos.

Silver-spotted Skipper butterfly

September 22, 2011


A Silver-spotted Skipper butterfly (Epargyreus clarus) feeding on Zinnia flowers (Zinnia sp.), spotted during a photowalk through the Children’s Garden, Hollin Meadows Science and Math Focus School. Silver-spotted Skipper is one of the easier-to-identify Skipper butterflies.

Scarlet milkweed seeds

September 8, 2011


Scarlet milkweed (Asclepias curassavica) seeds bursting from a seed pod, spotted during a photowalk through the Children’s Garden, Hollin Meadows Science and Math Focus School. Milkweed is a host plant for several types of insects, including the Monarch butterfly (Danaus plexippus).

Another summer sunflower

August 25, 2011


A sunflower (Helianthus annuus) spotted during a photowalk through the Children’s Garden at Hollin Meadows Science and Math Focus School. See also, “Sunflower, Bumble bee, and a black ant” (one of my recent Posterous posts).

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