Earth and Space News: American astronomer Joel Stebbins

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Wednesday, July 14, 2021

Joel Stebbins Determined Migrating Bird Speeds Via Telescopes in 1906

Summary: American astronomer Joel Stebbins determined migrating bird speeds via telescopes in 1906, according to his July 13, 1906, report in Science.

University of Illinois-Urbana astronomy professor and second Astronomical Observatory director Joel Stebbins collaborated with zoology professor Frederic Carpenter on projects on migrating birds in 1905 and 1906 at the University of Illinois Observatory; front yard shows Astronomical Observatory (right) and Observatory Annex (left), which was constructed 1914-1915; photo via Kevin Wright @ Champaign-Urbana History, Facebook, Jan. 6, 2020: Friends of the University of Illinois Observatory @U.of.Illinois.Observatory, via Facebook, Jan. 7, 2020

American astronomer Joel Stebbins determined migrating bird speeds via telescopes in 1906, according to his report in the July 13, 1906, issue of Science.

For his speed project, Joel Stebbins (July 30, 1878-March 16, 1966) built upon his spring and autumn 1905 project of determining migrating bird height via telescopes. On both projects the University of Illinois astronomy professor and Astronomical Observatory director teamed with University of Illinois zoology professor Frederic Walton Carpenter (May 12, 1876-March 1, 1925). Both projects concerned avian passage across the moon, according to the observers' perspectives. Both projects were conducted at the University of Illinois-Urbana Astronomical Observatory.

Stebbins and Carpenter used the same equatorial telescopes for both projects. Carpenter made his observations via a three-inch aperture telescope set on a movable tripod. Stebbins, who was stationed 200 feet north Carpenter, observed via a four-inch aperture telescope mounted on a fixed pier.

Stebbins described the method's theory as "simple enough" (page 50). With each bird sighted, Carpenter was charged with calling "time" when the bird exited the lunar disk. Stebbins then counted, in seconds, the elapsed time, from his viewpoint, for the bird to leave the disk. The bird's speed in miles per hour was based upon the interval between the two observed exits from the lunar disk.

Stebbins did not use a stopwatch as counter. He began his count with "and" one-half second after Carpenter called "time." He equated the interval between each "and" and number in his count to one-half second. Stebbins explained that years of experience, by both him and his teammate, in the "eye and ear method" of observing stellar transits, had refined their time sensitivity to greater accuracy than that achieved by a stopwatch.

Stebbins and Carpenter experienced favorable conditions for their migrating bird speed project on only one night during the spring 1906 migrating season. In the text, Friday, May 18, is given as the successful date. But in the data and results table, the date is identified as May 11. The table noted a southwest wind of 14 miles per hour.

On the successful date, Carpenter called "time" for 10 birds. Stebbins, however, only saw three of them.

The table detailed observation and travel times for each of the three mutually-observed birds. Birds 1, 2 and 3 were observed at 11:30 p.m., 11:38 p.m. and 11:50 p.m., respectively. Travel times of 1.0 seconds, 1.25 seconds and 1.0 seconds were clocked for birds 1, 2 and 3, respectively.

An allowance for the velocity of sound was deemed necessary. Accordingly, observed intervals were increased by 0.2 second. The corrected times for birds 1, 2 and 3 were given as 1.2 seconds (up from 1.0), 1.45 seconds (up from 1.25) and 1.2 seconds (up from 1.0), respectively.

The table assigned speeds of 114 miles per hour, 94 miles per hour and 114 miles per hour for birds 1, 2 and 3, respectively. Stebbins noted the speeds as minimum speeds to account for passage over more than 200 feet between observations by birds not flying due north. Although Stebbins and Carpenter focused on time estimates, they concluded that projected path directions revealed an actual flight direction of northeast.

In the period between 11:20 p.m. and 12:20 a.m. on the successful date, Carpenter observed a total of 35 birds. Stebbins tallied 15 birds.

Attempts on the two succeeding nights proved unsuccessful. Passing clouds and fewer avian fliers hindered observations.

Stebbins concluded his report with the suggestion of using three telescopes as a method for determining both heights and speeds as migrating birds fly across the lunar disk. Height data could be obtained by two observers spaced about 10 feet apart on an east-and-west line. A third observer, located about 100 yards to the north or south of the other observers, could gather speed data.

The takeaways for Joel Stebbins' determination of migrating bird speeds via telescopes in 1906 are that the University of Illinois-Urbana Astronomical Observatory director collaborated with University of Illinois zoology professor Frederic Walton Carpenter in building upon their spring and autumn 1905 project on migrating bird heights; unfavorable conditions restricted the project to one successful day in May; and Stebbins concluded that use of three telescopes could incorporate heights and speeds into one project.

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

The four-inch aperture telecope operated by Joel Stebbins during migrating bird observations was set on the fixed pier for his observations of migrating birds: Friends of the University of Illinois Observatory @U.of.Illinois.Observatory, via Facebook. July 29, 2017, @ https://www.facebook.com/U.of.Illinois.Observatory/photos/a.137983869590423/1372269032828561/

For further information:

Abbott, David. The Biographical Dictionary of Scientists: Astronomers. New York NY: Peter Bedrick Books, 1984.

Carpenter, Frederic W. "An Astronomical Determination of the Heights of Birds During Nocturnal Migration." The Auk, vol. 23, no. 2 (Apr., 1906): 210-217.
Available via JSTOR @ https://www.jstor.org/stable/4070753

"Carpenter, Frederic Walton." The National Cyclcopaedia of American Biography, vol. XX: 322-323. New York: James T. White & Company, 1929.
Available via HathiTrust @ https://hdl.handle.net/2027/mdp.39015078229088?urlappend=%3Bseq=708

Friends of the University of Illinois Observatory @U.of.Illinois.Observatory. "The back of the Observatory from about 1910. The south yard was always home to various smaller telescopes including a 4-inch refractor and later a 30-inch reflector. . . ." Facebook. July 29, 2017.
Available @ https://www.facebook.com/U.of.Illinois.Observatory/photos/a.137983869590423/1372269032828561/

Friends of the University of Illinois Observatory @U.of.Illinois.Observatory. "A new photograph of the Observatory and the dome for the 30-inch reflector!" (Photo via Kevin Wright @ Champaign-Urbana History, Facebook, Jan. 6, 2020.) Facebook, Jan. 7, 2020.
Available @ https://www.facebook.com/U.of.Illinois.Observatory/posts/2599571520098300

Marriner, Derdriu. "American Astronomer Joel Stebbins Pioneered Photoelectric Photometry." Earth and Space News. Wednesday, July 30, 2014.
Available @ https://earth-and-space-news.blogspot.com/2014/07/american-astronomer-joel-stebbins.html

Marriner, Derdriu. "Far Side Lunar Crater System Stebbins Honors American Astronomer Joel Stebbins." Earth and Space News. Wednesday, July 24, 2019.
Available @ https://earth-and-space-news.blogspot.com/2019/07/far-side-lunar-crater-system-stebbins.html

Marriner, Derdriu. "Joel Stebbins Determined Migrating Bird Heights Via Telescopes in 1905." Earth and Space News. Wednesday, Feb. 24, 2021.
Available @ https://earth-and-space-news.blogspot.com/2021/02/joel-stebbins-determined-migrating-bird.html

Marriner, Derdriu. "Joel Stebbins Observed Linné Crater During Feb. 8, 1906, Lunar Eclipse." Earth and Space News. Wednesday, Jan. 27, 2021.
Available @ https://earth-and-space-news.blogspot.com/2021/01/joel-stebbins-observed-linne-crater.html

Moore, Patrick, Sir. Astronomy Encyclopedia: An A-Z Guide to the Universe. New York NY: Oxford University Press, Inc., 2002.

Moore, Patrick, Sir. Philip’s Atlas of the Universe. Revised edition. London UK: Philip’s, 2005.

Scott, W.E.D. "Some Observations on the Migration of Birds." Bulletin of the Nuttall Ornithological Club, vol. VI, no. 2 (April 1881): 97-100. Cambridge MA: Nuttall Ornithological Club, 1881.
Available @ https://books.google.com/books?id=h3sVAAAAYAAJ

Stebbins, Joel. "A Method of Determining the Heights of Migrating Birds." Popular Astronomy, vol. XIV, no. 2, whole no. 132 (February 1906): 65-70.
Available via Harvard ADSABS (NASA Astrophysics Data System Abstracts) @ http://adsabs.harvard.edu/full/1906PA.....14...65S
Available via Harvard ADSABS (NASA Astrophysics Data System Abstracts) @ http://adsabs.harvard.edu/pdf/1906PA.....14...65S
Available via HathiTrust @ https://hdl.handle.net/2027/njp.32101075380152?urlappend=%3Bseq=95

Stebbins, Joel; and Edward A. Fath. "The Use of Astronomical Telescopes in Determining the Speeds of Migrating Birds." Science, vol. 24, issue 602 (July 13, 1906): 49-51.
Available @ https://science.sciencemag.org/content/24/602/49

Svec, Michael. "The Many Transformations of the University of Illinois Observatory Annex." Journal of Astronomical History and Heritage, vol. 21, issue 1 (March/April 2018), 81‒93(2018).
Available via NARIT (National Astronomical Research Institute of Thailand) @ http://old.narit.or.th/en/files/2018JAHHvol21/2018JAHH...21...81S.pdf

Very, Frank W. "Observations of the Passage of Migrating Birds Across the Lunar Disk on the Nights of September 23 and 24, 1896." Science New Series, Vol. 6, No. 141 (Sep. 10, 1897), pp. 409-411.
Available via JSTOR @ https://www.jstor.org/stable/1625184

Wednesday, February 24, 2021

Joel Stebbins Determined Migrating Bird Heights Via Telescopes in 1905

Summary: American astronomer Joel Stebbins determined migrating bird heights via telescopes in 1905, according to his February 1906 report in Popular Astronomy.

Illustration shows May 19, 1905, path of eighth bird, as charted by Joel Stebbins (S8) and Frederic Carpenter (C8), with Stebbins sited 21 feet east of Carpenter; J. Stebbins, "A Method of Determining the Heights of Migrating Birds," Popular Astronomy (February 1906), page 66: Public Domain, Google-digitized, via HathiTrust

American astronomer Joel Stebbins determined migrating bird heights via telescopes in 1905, according to his report in the February 1906 issue of Popular Astronomy.

During spring and autumn 1905, University of Illinois-Urbana astronomy professor and Astronomical Observatory director Joel Stebbins (July 30, 1878-March 16, 1966) teamed with University of Illinois-Urbana zoology professor Frederic Walton Carpenter (May 12, 1876-March 1, 1925) on a project to determine the heights achieved by migrating birds. The project took place on the grounds of the University of Illinois Observatory.

The duo's most successful observation sessions occurred on Friday, May 19, and Tuesday, October 10. Stebbins reported a total viewing of 78 separate birds within two and one-half hours on May 19. Carpenter recorded 34 birds, and Stebbins saw 33. Eleven birds were seen by both observers.

Within a two-hour period on Oct. 10, viewed birds totalled 57, with 11 recorded by both observers. Carpenter noted 29 birds while Stebbins espied 17.

The greatest range in avian altitude occurred on Oct. 10. Nine birds accounted for a variation of 1,400 to 5,400 feet. The greatest distance between any bird and the observers was 7,700 feet.

On May 19, the altitude of nine birds ranged from 1,200 to 2,400 feet. The greatest distance between the observers and any bird was 7,100 feet.

Error percentages were assigned to the altitude ranges for the two dates. The greatest height of 5,400 feet was deemed to have a possible error of 25 percent. Lower distances were considered to have a probable correctness of within 10 percent.

Stebbins noted the assumption held by previous observers of migratory bird height that altitudes of two to three miles or more were achievable. Contrarily, Stebbins and Carpenter experienced no heights of more than half a mile on May 19. The majority of that date's birds flew below 1,200 feet. While one or two birds flew "as high as a mile" on Oct. 10, most birds stayed below "1200 or 1500 feet" (page 70).

Stebbins and Carpenter's method entailed determining the parallax of each migrating bird. Parallax references the angle subtended by two sight-lines. They established the distance between their observation posts as the parallax's base line.

Stebbins and Carpenter used two small equatorial telescopes with different apertures. The four-inch aperture telescope was mounted on a fixed pier. The three-inch telescope was set on a movable tripod in order to allow for any direction or length for the base line of each bird's parallax. Experimentation revealed that a distance of 10 feet between observers established the best base line for lunar passage near the meridian, or the longitude of their location.

Placement of the telescopes at right angles to bird flight direction assured simplicity in observation and computation. Flight direction was established as northward in spring and southward in autumn. Specifically, Stebbins and Carpenter found in their observations that most birds averaged northwesterly flight in spring and southeasterly flight in autumn. The telescopes were sited on an east and west line.

Each telescope's eyepiece presented a power of about 25. Each eyepiece included all of the lunar disk within its field of view.

The placement of a reticle of four heavy crosshairs in the focal plane allowed for division of the field of view into octants. Rotation of the reticle continued until one of the crosshairs paralleled the moon's diurnal, or apparent daily, motion. During observation sessions, the intersection of the crosshairs centered on the circular arc of the lunar image. A bird's path was estimated from different crosshairs. Stebbins and Carpenter found that best observations usually occurred in the latter part of a bird's path across the lunar disk.

Stebbins noted that the observations conducted by Carpenter and himself apparently marked the first instance of usage of "this simple method" in determining migratory bird heights. He concluded that practice of the method at "many stations over the country" would yield valuable nocturnal flight data for ornithologists.

The takeaway for Joel Stebbins' determination of migrating bird heights via telescopes in 1905 is that the University of Illinois astronomy professor devised and tested, in collaboration with University of Illinois zoology professor Frederic Walton Carpenter, a method for calculating migrating bird heights, against the bright backdrop of the lunar disk, by establishing each bird's parallactic angle via two telescopes stationed 10 feet apart.

Illustration shows angles, axes and planes for computing migrating bird height, with B=bird, H=bird's height above ground, O=observer on east-west line, W=west, x=east, y=north; J. Stebbins, "A Method of Determining the Heights of Migrating Birds," Popular Astronomy (February 1906), page 68: Public Domain, Google-digitized, via HathiTrust

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Abbott, David. The Biographical Dictionary of Scientists: Astronomers. New York NY: Peter Bedrick Books, 1984.

"Carpenter, Frederic Walton." The National Cyclcopaedia of American Biography, vol. XX: 322-323. New York: James T. White & Company, 1929. Available via HathiTrust @ https://hdl.handle.net/2027/mdp.39015078229088?urlappend=%3Bseq=708

Consolmagno, Guy; and Dan M. Davis. Turn Left at Orion. Fourth edition. Cambridge UK; New York NY: Cambridge University Press, 2011.

Levy, David H. Skywatching. Revised and updated. San Francisco CA: Fog City Press, 1994.