Newsletter of the Desert Foothills Astronomy Club
Issue #10: February 3rd, 2007


About Quid Novi

Past Issues

DFAC Events

State of DFAC

Last Meeting

Next Meeting

Quote of the Month

Space Debris

Contact the Editor: Dan Heim, phone: 623.465.7307 or email:


DFAC Events:
Date   Time   Event   Location
Sep 27   7:00 pm - 9:00 pm   DFAC Lecture Meeting #1   Boulder Creek High School, 40404 North Gavilan Peak Parkway, Anthem, AZ 85086
Oct 25   7:00 pm - 9:00 pm   DFAC Lecture Meeting #2   Boulder Creek High School, 40404 North Gavilan Peak Parkway, Anthem, AZ 85086
Oct 30   5:30 pm - 8:00 pm   Ladies Guild Astronomy Night   6609 E. El Sendero Drive, Cave Creek, AZ 85331 (contact Dan Heim for gate code)
Nov 28   5:30 pm - 7:30 pm   Student Astronomy Night   Foothills Academy College Prep, 7191 E. Ashler Hills Drive, Scottsdale, AZ 85262
Nov 29   7:00 pm - 9:00 pm   DFAC Lecture Meeting #3   Boulder Creek High School, 40404 North Gavilan Peak Parkway, Anthem, AZ 85086
Jan 18   5:30 pm - 8:00 pm   Student Astronomy Night   New River Elementary School, 48827 N. Black Canyon HWY (Exit 232 east to frontage north)
Jan 31   7:00 pm - 9:00 pm   DFAC Lecture Meeting #4   Boulder Creek High School, 40404 North Gavilan Peak Parkway, Anthem, AZ 85086
Feb 28   7:00 pm - 9:00 pm   DFAC Lecture Meeting #5   Boulder Creek High School, 40404 North Gavilan Peak Parkway, Anthem, AZ 85086
Mar 10   6:00 pm - ?   DFAC Observing Session   Heimhenge
Mar 21   6:30 pm - 8:30 pm   Student Astronomy Night   Eastside Explorers HomeSchool Group, address TBA
Apr 25   7:00 pm - 9:00 pm   DFAC Lecture Meeting #6   Boulder Creek High School, 40404 North Gavilan Peak Parkway, Anthem, AZ 85086
May 30   7:00 pm - 9:00 pm   DFAC Business Meeting   Boulder Creek High School, 40404 North Gavilan Peak Parkway, Anthem, AZ 85086

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State of DFAC: By Dan Heim, President
  • Publicity: I got several calls and emails as a result of that "light pollution" article that recently ran in The Desert Advocate. If you missed it, see:

    http://www.thedesertadvocate.com/archives/ar011707/011707/comm/3.htm

    It's clear there's a significant public awareness and interest in this issue, but never enough, in my humble opinion. To that end, the Advocate will soon run another article I wrote titled "The Top 10 Reasons for Not Installing a Dusk-to-Dawn Mercury Vapor Yard Light" (also available for download on this website). In this article I offer, at no charge to civic and educational groups, the same Light Pollution lecture DFAC members saw at our first BCHS meeting. I'm willing to do as many of these as are requested in the interest of preserving our night sky.
  • Website: On that same topic, I've added a link to the Arizona Revised Statutes (Title 49 -The Environment, Chapter 7 - Light Pollution) on the Light Pollution page of our website. We already have links to the Maricopa and Yavapai County zoning ordinances for lighting (and the IDA) so this rounds it out. If anyone ever asks you about the laws that apply to lighting, refer them to our website for answers to all their questions. DFAC can use the publicity.
  • Lecture Series: Our Spring Lecture Series is now filled. Unavailable for that series were Dr. Jeff Hester or ASU (whose next lecture will be on "quantum cosmology") and Stan Gorodenski (owner-builder of Blue Hills Observatory up in Dewey, AZ). Both of these gentlemen have agreed to speak to us during our Fall Lecture series later this year. Stan and I go way back to the early 80's, when we were both members of PAS. He's just recently completed his custom-designed observatory and will talk to us about "What I did right, what I did wrong, and what I'd do different next time." You can visit his website and see what he's done at: http://users.commspeed.net/stanlep/HomePageNS.html.
  • Astronomy Night: Our final public event for the year is still a work in progress. Tentatively set for Wednesday, March 21st, we'll be with the Eastside Explorers HomeSchool Group. Like the Ladies Guild event, this one will feed our treasury. A donation, amount unspecified, has been promised. This will also be a large group (40-50) of adults and children, so we'll really need some scopes there. I'm still working to finalize the date and details, and will pass those along as soon as I can.
  • DFAC Observing Session: Looks like DFAC will finally have its first observing session. I've had several RSVPs already for the March 10th event, so (weather permitting) all systems are "go." The Moon is at 3rd quarter that night, as you all probably know, and the weather should be a bit more accommodating. Saturn, Jupiter, and Venus will all be good. Sunset is 6:30, so arrive around 6:00 to get set up. BYO. Restrooms provided. If you don't know how to find Heimhenge, email me and I'll send you a map. I'm looking forward to "first light" for my recently realigned Dob. [Thanks for loaning the laser collimator, Ken!]
  • Business Meeting: Our May business meeting is rapidly approaching. No members have yet indicated an interest in Officer positions for next year. Roger and I have discussed this, and we're both OK continuing in these positions for another year. This is a young club, and I think we need to increase our membership yet before reaching critical mass. At some point, we'll have enough members that someone will have the skills, time, and interest to step forward. I realize that "skills, time, and interest" are hard to find these days ... mainly the "time" part. But we'll get there eventually. This seems to say that a high priority for us now is to do some recruiting. Astronomy Nights for schools help, media visibility helps, and so does just spreading the word. Tell your neighbors and friends about DFAC, and twist some arms.
  • VP Needed: Still, it would be good to add at least one other Officer in May. DFAC needs a VP to act as stand-in (if I ever can't make it to a meeting) and to assist in the scheduling of speakers for our Lecture Series. This is probably the most essential position to add at this point. If you think you can do this for DFAC, let me know and we'll put you on the May ballot. Thanks.
  • BCHS: Our agreement with BCHS included our doing an Astronomy Night for their community. This is how we pay our rent for the facility. Since our faculty liaison left the school, no other faculty member has volunteered for the position. For that reason, they also still don't have a student Astronomy Club. The bottom line is, I don't think we'll be doing an Astronomy Night for BCHS this first year. They need to get the staff infrastructure assembled on their end before these kinds of thing can happen. I am communicating with Kevin Imes on this topic, and will keep you posted on developments.
  • Thanks for reading Quid Novi. You know where to send your feedback. Clear skies!

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Last Meeting: Wednesday, January 31st, 2007
Dan Heim spoke to our group on the topic of "Amazing Astronomy Multimedia Online," including audio, video, and still image content. We heard Ray Bradbury speaking to us from the surface of Mars, took a 3D fly-through of the Orion Nebula, and puzzled over a simulation of the Mars analemma. This puzzle, by the way, has since been resolved (see Space Debris below). Dan also shared his catch from the recent Mercury transit, including stills and a time-lapse sequence of 3rd-4th contact. Some of these images are now posted on the Astrophotos page of this website. Check them out for a higher contrast view than we had at BCHS.

Speaking of bad contrast, the doors opened late, due to a communications glitch, so we were didn't have the time to disable those unswitched lights that pollute the projection screen. Trust that we are working to resolve this problem. As a last resort, we can manually disconnect the fluorescent bulbs. It's just a matter of climbing up on a chair on top of a table ... but there's gotta be an easier way.

It was a good turnout despite lousy weather. We had 9 members in attendance, all of whom stayed for the entire program. We thank these hardy souls for venturing out that rainy night. Feedback indicates the drive was worth it, as all enjoyed the show and participated in some lively discussion.

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Next Meeting: Wednesday, February 28th, 2007
Our February speaker will be Dr. John Fountain, recently retired of the UofA Lunar and Planetary Laboratory. He will enluighten us on the topic of Archaeoastronomy (not Astroarchaeology). Here's a short excerpt from his bio:

John Fountain began his study of the moon and planets while an undergraduate at the University of Arizona, helping to analyze the first spacecraft pictures of the moon returned by the Ranger Project. He co-authored the Consolidated Lunar Atlas which was used by the Apollo astronauts. Earthbased imaging of the planets in support of NASA missions occupied much of his career. He is the codiscoverer of two satellites of Saturn, and he deduced the thickness and distribution of material in the Saturn rings from earthbased observations. He supervised production of the images from the first missions to Jupiter and Saturn by the Pioneer 10 and I I Spacecraft. He was also a participant in the Mariner and Voyager missions.

Some 15 years ago he began a serious investigation of astronomical references in the ancient rock art of North American Indians. His work shows that pre-Columbian Native Americans placed rock art in such a way that beams of sunlight interact with the rock images on important seasonal days such as equinoxes and solstices. Such markers often have remarkably high precision. In addition to his own studies of numerous rock art sites, he has established a database of rock art solar markers which demonstrates they were surprisingly common and widespread. He has also done research on geoglyphs and Oriental archaeoastronomy. He has led archaeoastronomy tours for Crow Canyon Archaeological Center and was featured in the KUAT-TV production of The Desert Speaks - Shadows of the Ancients. He is co-editor of the book Current Studies in Archaeoastronomy: Conversations Across Time and Space, and has published 35 scientific papers.

This should be a truly fascinating lecture. We hope to see you all there.

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Quote of the Month:
[On the topic of alien intelligences as portrayed in science fiction] "So far as I know, every such story has alien intelligences which treat humans as approximate equals, either as friends or foes. It is assumed that A-I will either be friends, anxious to communicate and trade, or enemies who will fight and kill, or possibly enslave, the human race. There is another and more humiliating possibility alien intelligences so superior to us and so indifferent to us as to be almost unaware of us. They do not even covet the surface of the planet where we live they live in the stratosphere. We do not know whether they evolved here or elsewhere will never know. Our mightiest engineering formations they regard as coral formations, i.e., seldom noticed and considered of no importance. We aren't even nuisances to them. And they are no threat to us, except that their engineering might occasionally disturb our habitat, as the grading done for a highway disturbs gopher holes. Some few of them might study us casually or might not."

— Robert A. Heinlein, "Grumbles from the Grave"

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Space Debris:
Are you ready for an astronomy lesson? Good, because we'll have a test on this at our next meeting. :) We belong to DFAC in part to learn, so here goes ...

At our January 31 meeting, we discussed the unusual shape of a simulated Mars analemma. I expressed my puzzlement regarding where the equinoxes fit in. It was suggested that perhaps we were only seeing half the total analemma, even though the image was labeled "Martian analemma" and not "half the Martian analemma." I pleased to report I have solved the mystery, and in the process learned something valuable about the Earth analemma as well.

First, the image in question, downloaded from the Astronomy Picture of the Day website. See: http://antwrp.gsfc.nasa.gov/apod/ap061230.html.

What puzzled us (or perhaps I should say "What puzzled me") was where the equinoxes were on this curve. On the familiar Earth analemma the equinoxes are at the intersection of the "figure-8" curve. Or so I had thought ... turns out they are close to that intersection point, but not exactly on it. Here's what I learned by doing a little research. For any planet, the analemma is a superposition of two sine waves, much like the Lissajous figures you can get on a dual trace oscilloscope. [See: http://www.ngsir.netfirms.com/englishhtm/Lissajous.htm for a java demo of this effect.] For an analemma, one sine wave is due to the planet's equatorial inclination; the other is due to the orbital eccentricity. Either alone would cause the Sun to oscillate sinusoidally along a single axis (vertical for inclination, and horizontal for eccentricity). What complicates things is, these two sine waves have different lengths, amplitudes, and phase. The result is an irregular Lissajous figure. See: http://en.wikipedia.org/wiki/Equation_of_time.

The equinox occurs when the planet's polar axis lies in a plane tangent to its orbit, causing the Sun to appear directly overhead at the equator. On Earth, that's March 20 and Sep 23 (1 day). On the analemma, those points would by definition be located exactly halfway between the top (dec +23.5)and bottom (dec -23.5) of the curve. In other words, the Sun would have a declination of exactly zero. No problem there. That's fairly easy to visualize.

The real epiphany occurred when I looked at a labeled higher resolution image of the Earth analemma (image below). It became immediately obvious that my assumption was wrong. When you only look at pretty astrophotos of the analemma, or the crude one often stamped on Earth globes, and don't really think about it critically, you can end up with bad science. And that's exactly what I had done. The equinoxes are most definitely not at the intersection point. The fact that they're even close to the intersection point is a geometric coincidence. They must be located where the declination is zero, and since the analemma is asymmetric, the intersection point can't possibly be the equinoxes. So for all these years, I had incorrectly assumed the equinoxes had to be at the intersection point. I'm embarrassed to say I even taught that "fact" for 22 years. Mea culpa.

The east-west extent of the analemma is a function of the orbital eccentricity. As the planet approaches perihelion (increasing in speed) the Sun gains on clock time. Approaching aphelion, the opposite occurs. Note how the four points at which Sun time agrees with clock time are asymmetrically located. Surprisingly (at first), the points at which clock time agrees with Sun time do not occur at perihelion and aphelion. The fact that perihelion and winter solstice don't occur on the same date skews the analemma clockwise slightly. Note on the Earth analemma how the zero point is reached on June 15 (17 days before the July 3 aphelion) and Dec 25 (8 days before the Jan 2 perihelion). The intersection point (Apr 13 & Aug 30) is also not a zero point. This skewing can be explained as the result of the phase difference in these two sinusoidal cycles.

It's also important to note that the precise shape of the analemma depends critically on both latitude and the time of day the Sun is imaged. The original Mars analemma image was simulated as visible from Sagan Memorial Station, home of the Sojourner Rover, for an unspecified time in the "late afternoon." Below is a graphic comparison of Earth and Mars analemmas, compared side by side, both for 45 latitude at noon.

I'll close this with one last interesting point. Not surprisingly, the analemma looks different on every planet. Here's a tabulation of the shape geometry for our Solar System:

Mercury: nearly straight east-west line
Venus: ellipse
Earth: figure-8
Mars: teardrop
Jupiter: ellipse
Saturn: figure-8 (but the top loop is so small it's essentially a teardrop)
Uranus: figure-8
Neptune: figure-8
Pluto: figure-8 (yeah, I know it's not a major planet anymore)

So now you know all about the analemma. Probably more than you ever wanted to. If you still have a thirst for more, and want to understand the math behind all this, download the 46-page PDF titled "The Analemma for Latitudinally Challenged People" by Helmer Aslaksan and Shin Yeow Teo by clicking here (1.7Mb).

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