In the "Tools" menu of Adobe Reader, be sure to specify Rotate > Counterclockwise to view the star maps in their intended landscape orientation.
Map 1 is a rectangular projection of the entire celestial sphere onto a plane. The stars are grouped into constellations by pattern lines. Pattern lines facilitate memorization of the appearance of the night sky, while the constellations themselves provide a framework for locating the brighter planets, stars, and other celestial objects.
Map 1 is "unbiased" because it is never completely upside down. For if north is up and you rotate the map 180 degrees, south is now up and you can still read the map's upper celestial hemisphere labels right-side up (try it).
Note the right ascension (RA) scales on the upper and lower borders of Map 1. These allow you to determine the local apparent sidereal time at your longitude by the following two rules.
Rule 1 - Locate Celestial Meridian at Midnight on Given Date
To find the RA of the stars crossing your celestial meridian at midnight on a given date, use the dates and the RA scale for your geographical hemisphere (northern or southern based upon your latitude) as a guide to estimating the placement of a line perpendicular to the RA scales and passing through the given date on both RA scales. This perpendicular line is your celestial meridian line at midnight. Note that each "tick" on the RA scale corresponds to about four calendar days as well as to exactly 15 minutes of RA.
Rule 2 - Locate Celestial Meridian at Given Hour on Rule 1 Date
To locate the celestial meridian at a given hour on the date used for Rule 1, move the celestial meridian line west (decreasing RA) one hour of RA for each hour earlier than midnight. Move the celestial meridian line east (increasing RA) one hour of RA for each hour later than midnight.
Since the celestial meridian is the extension of the great circle of your geographical longitude onto the celestial sphere, it marks the local apparent sidereal time. Its location in the sky at any point in time tells you what stars and constellations you can see as you look south (northern hemisphere observer) or north (southern hemisphere observer) along the celestial meridian.
Map 2 is a polar equidistant projection of the north celestial hemisphere onto a plane, plus another 45 degrees of southern declination. It is therefore good for northern hemisphere observers.
Map 3 is a polar equidistant projection of the south celestial hemisphere onto a plane, plus another 45 degrees of northern declination. It is therefore good for southern hemisphere observers.
The 57 celestial navigation stars are labeled on all three maps, where visible, plus other bright stars as indicated on the maps.
Dr. Barbara D. Buchalter (1929 April 13 - 2005 November 26)
Professor of Mathematics, University of Nebraska at Omaha
"Dr. Buchalter taught me Complex Variables and Conformal Mapping"
This concludes the information about my presentation to the Rocky Mountain Section of the MAA.
Back to Top
This concludes my webpage topic "Reconstruction of the 1801 Discovery Orbit of Ceres." Please click on the link below to go back to the top of this webpage.
Back to Top
Trajectories of three Newtonian particles numerically integrated using Mathcad Prime 1.0.
"Nonlinear Dynamics Using Mathcad Prime 1.0"
is the title of a presentation that I recorded at PTC World Headquarters in Needham, Massachusetts on March 15, 2011 -- for viewing at the PlanetPTC Virtual Mathcad Event held on April 14, 2011.
My goal in the presentation was to show that, while Mathcad Prime 1.0 is not yet ready to take over the role of Mathcad 15, one can nevertheless use it right now to do some rather sophisticated nonlinear dynamical modeling.
To see what I mean, consider the figure above. It looks like black, red, and blue scribbles as might have been made by a child using colored pens or crayons.
But in fact the figure is the result of integrating numerically the trajectories of three massive particles obeying the three highly-nonlinear, second-order, ordinary differential equations embodied in Newton's universal law of gravitation.
For an animation of the figure, see
For the particulars of my presentation, including all worksheets in both Mathcad and PDF format, visit
Back to Top
Mathematical Heart Surface plotted via Mathcad 15 and posted to PlanetPTC.
PlanetPTC is the union of new online PTC communities that includes users of the CAD programs Creo Elements/Pro (formerly Pro/ENGINEER) and Mathcad, as developed by Parametric Technology Corporation (PTC) of Needham, Massachusetts USA.
To see a clickable list of all of the PTC communities, click on
To go directly to the PTC Mathcad community, click on
In January 2011, Dan Marotta, the PlanetPTC webmaster, challenged Mathcad users to draw a heart surface such as was shown at the German website
Mathematische Basteleien (Mathematical Tinkerings). I responded with the plot shown above. It is actually a "pointillist" plot, i.e., it is a 3D scatter plot of points lying on the surface of the heart.
The mathematical heart surface depicted above has both bilateral (side-to-side) and dorsal-ventral (back-to-front) symmetry. I needed to take advantage of these symmetries in order that my plot not take too long to calculate in Mathcad. I discuss how I constructed this plot in the Mathcad worksheet posted at
If you do not have Mathcad 15, you can view my worksheet as a PDF file by clicking on Mathematical_Heart.pdf.
Anatomy enthusiasts will note that the mammalian heart has neither of the two true symmetries of the mathematical heart depicted above.
This is because, although the mammalian heart has left and right atria and ventricles, suggesting at least bilateral symmetry, the "blue" (oxygen-depleted) blood returns from the body to the right atrium and is pumped to the right ventricle, and then on to the lungs, while "red" (oxygen-enriched) blood returns from the lungs to the left atrium and is pumped to the left ventricle, and then on to the body via the aortic artery.
Why do I mention the mammalian heart in this context? Because there is actually an animation of a beating mammalian heart in the Mathcad videos at PlanetPTC. To see it, click on the link
Back to Top
Tautochrone Balls animation featured in PTC Express Newsletter of August 2010.
Four balls, initially at rest, are poised to slide down a curved path, as illustrated in the figure above. Assume that the balls are acted upon by the downward pull of gravity alone, with no rolling friction nor wind resistance.
Which ball will be the first to arrive at the bottom of the curve, at the point x = pi, y = -2?
For the answer, go to the Mathcad 15 video posted at
http://communities.ptc.com/videos/1344. The answer may not be what you expect.
The Mathcad 15 worksheet is available for download from the August 2010 issue of PTC Express. If you do not have Mathcad 15, you can view the Tautochrone Balls worksheet as a PDF file by clicking on Tautochrone_Balls.pdf.
Back to Top
View from Denver, Colorado at midnight on 2009 February 28. Pointer marks epsilon Aurigae.
Post of March 2011:
Mystery Solved! Thanks to the technical leadership, diligence, and perseverance of Dr. Bob Stencel and Mr. Jeff Hopkins, and with the collaboration of an international team of professional and amateur astronomers, the nature of the stellar system epsilon Aurigae has at last been elucidated.
For full details, go to Dr. Bob's University of Denver (DU) Portfolio page at
and download the PDF file with the title, "IR results on epsilon Aurigae, Jan.2011 PDF". This poster paper, presented at the AAS conference in Seattle, Washington USA in January 2011, is as visually appealing as it is informative.
Post of February 2009:
Epsilon Aurigae excitement builds as the next minimum of this mysterious stellar system nears (August 2009). The German astrophysicist Hans Ludendorff (1873-1941) brought epsilon Aurigae to the attention of the world astronomical community early in the 20th century, with the publication of two seminal papers that characterized the eclipses of 1847-48, 1874-75, and 1901-02.
But Ludendorff's papers apparently had never been translated into English. Therefore, to assist in the work of the Epsilon Aurigae Eclipse Campaign 2009-2011, I have translated from German to English Ludendorff's two main papers on epsilon Aurigae,
"Untersuchungen ueber den Lichtwechsel von epsilon Aurigae," Astronomische Nachrichten (A.N.), Vol. 164, pp. 81-114 (1904), and
"Bearbeitung der Schmidtschen Beobachtungen des Veraenderlichen epsilon Aurigae," A.N., Vol. 192, pp. 389-406 (1912).
My English translations, and the original articles in German, are now available for downloading from Jeff Hopkins's HPOSoft website, at
(Look under the heading, "Conversions of Ludendorff's 1904 and 1912 publications from German to English by Roger Mansfield of Astronomical Data Service".)
For further information about the Epsilon Aurigae Eclipse Campaign 2009-2011, click on Dr. Robert E. Stencel's Epsilon Aurigae Eclipse Campaign Homepage at
And be sure to read Dr. Stencel's feature article, "The Very Long Mystery of Epsilon Aurigae," beginning on p. 58 in the May 2009 issue of Sky & Telescope!
Back to Top
Predicting Iridium Flares is a webpage that predicted the Iridium flares visible from Boulder, Colorado U.S.A.
during the period Sunday, April 27 through Saturday, May 3, 2008.
This webpage page was prepared for use by attendees at the Division on Dynamical Astronomy (DDA) 2008 Meeting of the American
Astronomical Society (AAS), April 28 - May 1, as hosted by the Southwest Research Institute (SwRI), 1050 Walnut Street,
Suite 300, Boulder, Colorado 80302.
The webpage was provided as a supplement to my DDA 2008 poster presentation, "Predicting Iridium Flares." Click on
to see the Iridium flare predictions that were made for the DDA meeting. (A concise, half-page, printed
summary flyer was also distributed to attendees at the DDA meeting, via the registration desk.)
For more information about the DDA 2008 meeting, click on
To see the followup article, "Predicting Iridium Flares," which was published in the May 2008
issue of PTC Express, monthly newsletter of Parametric Technology Corporation, click on
Back to Top
Mathcad Worksheets by Astroger describes twelve Mathcad worksheets available for downloading
from Mathsoft's website. These worksheets implement key algorithms in dynamical astronomy and astrodynamics. Go to
Back to Top
Topics in Astrodynamics describes my astrodynamics textbook of the same name, and provides
resources toward using the book to teach a two-semester course sequence, Astrodynamics I and
Astrodynamics II. Go to
Back to Top
Orbital Mechanics with Mathcad lists the lesson plan topics for my
five-day, eight-hours-per-day course for space professionals in Colorado
Springs. For further information go to
(Other venues besides Colorado Springs are possible. Inquire at the e-mail address at the end of the astrocourse webpage.)
Back to Top
Space Ornithology is a webpage that documents my contributions to artificial Earth satellite observation as regards (a) writing and publishing the Space Birds computer program in 1987, and (b) coining the term space ornithology as the study of the space bird population (satellites in low-Earth orbit visible with the naked eye), and (c) publishing sixteen quarterly issues of the Space Ornithology Newsletter during 1988-1991. Go to
Back to Top
How I Got Started in Dynamical Astronomy and Astrodynamics
In the decade after the launch of Sputnik I, the U.S. Air Force took great strides in space
technology under the leadership of military space pioneers such as General Bernard A. Schriever and Dr. Louis G. Walters (for some recent links mentioning Dr. Walters and the Aeronutronic Division of Ford Motor Company, see the Wikipedia entries
Project_Space_Track (1957-1961), and
New career fields opened up for satellite controllers
and for orbital analysts. Professional space training for these new space career fields was set up at Keesler Air Force Base, Mississippi.
I attended two courses as a part of this new "Cold War" professional space training: the
three-week Space Operations Officer Course and the eight-week Orbital Analyst Course. My
fire for orbital mechanics was kindled at the first course and intensified at the
second. In my post-service career, I actively and successfully sought opportunities to do
orbital mechanics for a living, and to teach orbital mechanics (i.e., astrodynamics) as well.
Much of the orbital mechanics that I was doing applies to natural
celestial bodies and space probes as well as to artificial Earth satellites. And so
my interests began to encompass dynamical astronomy as well as astrodynamics. These
Astroger Webpages are thus devoted to both fields.
*Astroger is the union of the letters in "Astro" and the letters of my first name, "roger". Astroger is pronounced "Astro-jer" (soft "g"). It is actually a word, perhaps a contraction of "astrologer." I take "astroger" not to mean an astrologer, but rather "one who calculates trajectories using the principles of orbital mechanics."
Back to Top
Site5 hosts these Astroger webpages.
FileZilla uploads the content.
StatCounter counts the visitors ("Accesses" -- see below).
(c) 2011-2018 by Astronomical Data Service. Last updated 2018 April 09.