Sandburg S-E-M Day 2002

Sandburg Center for Sky Awareness
A Fairfax County Public Schools Planetarium

Sandburg "Sun-Earth-Moon Day 2002"

In celebration of Space Day, the Sandburg Planetarium hosted "Sun-Earth-Moon Day - Making the Sun-Earth Connection."¹

On Monday, 06 May, amateur astronomers from the Maryland Sidewalk Astronomers (MSA), National Capital Astronomers (NCA), Northern Virginia Astronomy Club (NOVAC), and Shenandoah Astronomical Society (SAS) visited Sandburg MS for a day of safe solar observation,² sundialing, and Moon-watching. Sincere thanks to Neil Feldman (MSA), Andrew Seacord (NCA), John Avellone (NOVAC), and Bill Devlin (SAS)--at CSMS, we appreciate your spirit of volunteerism and willingness to share your expertise and enthusiasm for observational astronomy! And of course, thanks to the following Sandburg Grade 8 Physical Science teachers for allowing their classes to participate in the special event: Mr. Daugherty, Ms. Hayes, Ms. Hayward, Ms. Smetana, and Ms. Wallace.

¹   The Sandburg Center for Sky Awareness (SCSA) prepared a special Web page of theme-related suggested teaching strategies, including pointers to electronic resources and classroom-ready activities: Me and My Shadow - Making the Sun-Earth Connection.
²   Disclaimer: NEVER look directly at the Sun, especially when using an optical device such as a camera, binoculars, or telescope--blindness may result! With the exception of the "Solar ProjectorScope" (that enables indirect viewing of the Sun's image), every telescope used during this event was equipped with a solar filter that permits only about 1/1000 of 1% of the incoming solar radiation to enter the telescope! Safely view near-real-time solar imagery (including sunspot imagery) by visiting the SOHO Images Web site (SOlar and Heliospheric Observatory).
³   Editor's Note: Experience has shown that an equatorial sundial is better suited for making the connection between the Earth's rotation and solar time-keeping, as well as the Earth's revolution around the Sun and the annual cycle of change in the Sun's apparent path across the sky.

(Storyboard reads left-to-right, top-to-bottom. Click on thumbnailed images for larger view.)

Mr. Sanford, Sandburg Planetarium Teacher, welcomes Sandburg MS Grade 8 Science students to Sun-Earth-Moon Day (S-E-M Day), introduces our guests, and reviews guidelines for safe solar observation and safe Sun exposure, warning students of the risk of blindness and overexposure to UV radiation.


John Avellone (left) and Andrew Seacord (right) make last-minute preparations while awaiting the arrival of the first classes....	Students visit with Bill Devlin, sundial enthusiast from Front Royal, VA. Our sincere thanks to Bill for travelling so far to share his expertise with FCPS students! Bill used a vast array of sundial stuff (covering two tables) to conduct demonstrations that helped to make abstract sundial theory more concrete and understandable--good show, Bill! For details, see Sundialing with Bill Devlin.


Mid-morning, Sandburg students were joined by special guests from the Stratford Landing ES (SLES) Gifted & Talented Center. To prepare students for participation in S-E-M Day, Mr. Sanford visited Ms. Waller (upper left, center) and Ms. White's (upper left, right) team-taught Grade Level 6 class on Friday, 03 May. Students were introduced to basic sundial theory, and assembled two types of sundials: the Sandburg Sundial (54k PDF), a customized ready-to-use horizontal sundial; as well as an equatorial sundial,³ courtesy NASA Liftoff to Space Exploration.

Mr. Devlin demonstrates how horizontal sundials actually work (above left & right). The dial plate must be horizontal (hence the name, "horizontal sundial"), and the gnomon (shadow caster) must form an angle equal to the latitude of the observer so that the style (top edge of the gnomon) is parallel to the Earth's axis. A properly aligned sundial shows Standard Time, after correcting for the longitudinal offset from the Standard Time Meridian, the Equation of Time, and Daylight Saving Time.

Bill demonstrates how a "pickle jar bowstring equatorial sundial" works (above left & right). The bowstring equatorial sundial is a close relative of the equatorial sundial template that SLES students assembled (see photos below). See firsthand a four-foot diameter bronze bowstring equatorial sundial by visiting the Garden of Time at Fairfax Memorial Park on Braddock Road, one mile east of George Mason University, Fairfax, VA.


With careful guidance from Bill & Eva Devlin (upper left), students put a little theory into practice by experimenting with the sundials they assembled....

Hmmm, what's wrong with this picture? Look closely. The first thing you may notice is that the time shown by the equatorial sundial (left) and the horizontal sundial (right) is not the same! A closer examination of the equatorial sundial reveals two problems: first, the Southern Hemisphere sundial template was mistakenly assembled as if it were the upper dial face of an equatorial sundial (actually, it should be the lower dial face); second, notice that the dial face itself is incorrectly numbered--Houston, we have a problem! [Please notify the responsible NASA Webmaster.] That said, if the equatorial sundial upper dial face were properly numbered (as it is on the Northern Hemisphere template), with 6 a.m. on the right side of the dial face, 6 p.m. on left, and the correct numbers shown between 6 a.m. and 12 noon, then the time would read approximately 10 a.m.--about the same time shown by the horizontal sundial!

Sidebar Activities

All students were reminded that the Sun is a star that radiates energy at all wavelengths of the electromagnetic spectrum; some wavelengths of solar radiation, e.g., ultraviolet radiation, are hazardous to plants and animals. Students were introduced to the UV Index as a measure of the risk of overexposure to the Sun. A UV Index Solarmeter (courtesy EPA SunWise School Program) was used to measure the UV Index periodically during the day.

SLES students used a tape measure and the SCSA Object Height Calculator to calculate the height of the tallest flagpole in front of Sandburg MS.

Andrew Seacord's large-aperture telescope (upper left), an 8-inch Celestron Schmidt-Cassegrain telescope equipped with a solar filter from Orion Telescopes & Binoculars, reveals spectacular detail in the many large sunspots that were visible on S-E-M Day (the daily sunspot number was 317!). Interested students have a blast (my apologies, I couldn't resist!) learning about solar science from Mr. Seacord, a semi-retired professional astronomer.

Avid telescope builder John Avellone does double-duty, manning two telescopes: NOVAC's 70mm f/10 equatorial-mounted motor-driven refractor telescope fitted with the Coronado Instruments "SolarMax" Hydrogen alpha (H alpha) filter for safely viewing the Sun's chromosphere and solar prominences (black & gold telescope shown right, left side of picture); and a homemade 6" f/8 solar telescope (based upon John Dobson's original solar telescope design) that enables completely safe viewing of the entire solar disc and all visible sunspots (right, center).


John Avellone adjusts a solar telescope equipped with a Coronado Instruments H alpha filter, enabling students to observe spectacular views of solar prominences similar to the ones shown in the photographs above (images courtesy Coronado Instruments Image Gallery). The H alpha filter isolates a one-Angstrom (0.1 Micron) region of the optical spectrum, centered on a wavelength of 6563 Angstroms (deep red). By looking only at this wavelength of light, contrast with the sky (which does not emit H alpha light) is maximized. Hence, the glowing hydrogen gas prominences streaming out from the solar limb are visible. Further, because of the narrow spectral passband of the filter (slightly less than 1 Angstrom), features generated by the motions of hydrogen gas in the photosphere, the outer layer of the Sun, also can be seen. See near-real-time H-alpha imagery by visiting the Latest Images Web page, courtesy Big Bear Solar Observatory.

Upper left (two pictures): A group of Ms. Wallace's students listen intently as Mr. Sanford explains how the ingeniously simple design of the Dobsonian solar telescope enables safe solar observation. Sunlight enters the telescope through a two-way mirror (most of the incoming sunlight reflects off the surface of the mirror before entering the telescope) and travels the length of the telescope before it "reflects" off the surface of a large, unsilvered mirror at the bottom of the tube. Light then travels back up the length of the telescope and is redirected into a low power eyepiece (near the top of the tube) after passing through a No. 10 welder's glass. Simple. Inexpensive. Completely safe!

Upper right: A young woman looks through the Dobsonian solar telescope (center) while Mr. Neil Feldman shares his enthusiasm for firsthand observation of astronomical phenomena such as sunspots. Meanwhile, Mr. Sanford (far right) realigns the "Solar ProjectorScope" for the next group of observers. This ingenius homemade telescope, designed & built by John Avellone for the Sandburg Planetarium, uses a repurposed "department store" telescope to project a 5-inch diameter image of the Sun inside a "dark box" enabling completely safe sunspot viewing.

Mr. Feldman realigns the Dobsonian solar telescope with the Sun. Because the Earth rotates, manual telescopes must be realigned frequently to keep the observing target within the telescope's field of view.

Our sincere thanks to Mr. Feldman for generously donating to the Sandburg Center for Sky Awareness the Dobsonian solar telescope (shown left, center), actually constructed by John Dobson, reknowned amateur astronomer and founder of the San Francisco Sidewalk Astronomers.


The experts agree, your first telescope should be a good pair of binoculars! Students take turns using an inexpensive pair of Tasco 10x50 binoculars, tripod-mounted for stability, to observe the Waning Crescent Moon (28% of the Moon's visible disk illuminated). In the glare of the Sun, the Moon showed very little contrast, making it difficult to see otherwise obvious lunar surface features such as prominent craters. By midday, Moon-watching was a washout! Grade Level 8 Science students study astronomy and Moon phases during the 4th quarter. For more information regarding observational astronomy, visit the SCSA Basic Tools of the Skywatcher/Amateur Astronomer Web page.

Photographs courtesy Judy Kramer, Sandburg MS Enrichment Specialist,
and Petra Pair, Sandburg School-Based Technology Specialist.
Thumbnail images prepared using photoweb v1.2 by Phil Wherry.

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