From the Director

by Rex Parker, Phd

Next meeting by Zoom on March 09 at 7:30pm.  The recurring dream of getting together for astronomy in Princeton’s Peyton Hall hasn’t faded, but again this month and for the rest of this season AAAP will meet virtually via Zoom.  For the March meeting our astronomy speaker will Zoom in from Nashville Tennessee – see the section below by Program Chair Victor Davis for more information about the program.  Also please note in Victor’s section a discussion of our intention to live stream and record on our dedicated You Tube channel the program section of AAAP meetings.

All systems are (almost) go for Observatory repair. The countdown has begun and the Observatory reconstruction project should lift off soon.  That might be a bit optimistic, but the bottleneck has been overcome.  We finally received a written response from the state officials in charge of reviewing construction plans at the Park.  Therefore we’ve initiated the formal permit request process.  A masonry contractor has been identified and an estimate obtained.  Once the application review and permitting are done the project should get off the ground, hopefully this spring. 

Because the reconstruction expense will take a significant chunk out of the treasury, we formed the Gene Ramsey Memorial Reconstruction Fund.  Contributions from members are a great way to honor Gene, who did so much for many years for the AAAP and the Observatory.  Under review is how to memorialize Gene in this project, maybe a bronze plaque affixed to the new column.  Your ideas on this are welcome — please send me an e-mail or comment during upcoming meetings. Donating now will also help ensure the future of our efforts to bring telescope observing and video astronomy to members and the public and kids.  Donations can be made directly and securely on the AAAP website (the yellow “Donate” button on the right side of the home page), or checks can be mailed to:  Treasurer, Amateur Astronomers Assoc. of Princeton, Inc., PO Box 2017, Princeton, NJ 08543.  For larger amounts a check is helpful because the PayPal fee is significant.  Contributions are tax-deductible.  Please consider corporate matching if it’s an option for you.

Mars rocks. Ever since the Viking landers studied Martian geology — but didn’t quite answer the biology question — the quest for evidence of life present or past on Mars has lured open minded thinkers and some of the world’s best engineers and scientists.  The Vikings were technological marvels of the 70’s – remember that Viking-1 landed on Mars exactly 7 years after Apollo 11 landed on the moon.  Last week NASA’s 5th rover, Perseverance, landed amidst a swirl of red dust as we watched entranced.  AAAP members answered the call to join the NASA Night Sky Network, with the AAAP-NSN roster now counting 45.  It was great to see a AAAP presence at the NSN Mars landing party just ahead of Perseverance’s feat on Feb 18.  The session included a display of member’s Mars images and the amazing photo by AAAP member Bob Vanderbei from last fall was the first one shown (and longest displayed) in the NSN live Zoom session.  There will be more cool events with this group in the future, so if you haven’t yet joined the Night Sky Network as a AAAP affiliate member, send a note to me or to Dave (AAAP-NSN coordinators) for the instruction set.

A different way of looking at the Drake equation.  In the early 1960’s astronomer Frank Drake formulated an equation that has never been solved.  It helped promote wider understanding and interest in the SETI quest. The equation was really meant more as a provocative tool than a solvable algebraic formula. As astrophysicist and Harvard Astronomy Dept Chair Avi Loeb says in his new book “Extraterrestrial:  The First Sign of Intelligent Life Beyond Earth” (2021, HMH Books), it’s unlikely we will ever be able to plug in values for all of the Drake variables, let alone determine their output.  One of several new ideas that Dr Loeb brings to the “Are we alone?” question in the book is the concept that we should be more prepared to look for evidence of astro-archaeology rather than extant life.  He explores the idea that civilizations may “wink in and out of existence”, perhaps inevitably and serially, over the unfathomably long history of the universe.  This might serve as a powerful warning for our own civilization.

Some may not know that Dr Loeb was a post-doc at the Institute for Advanced Study here (1988-1993), and the strong Princeton connections in the book will be familiar to AAAP members.  In the book Dr Loeb shows how the existing paradigm of astronomy and science needs to change, and how it might be able to, in order to see this question differently.  This important work is central to the interests of most AAAP members.  This is why I am challenging all AAAP members to read the book for a discussion at the March meeting.

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From the Program Director

by Victor Davis

The March 2021 meeting of the AAAP will take place (virtually) on Tuesday, 9th at 7:30 PM. (See Joining the Meeting with Zoom below for details). This meeting is open to AAAP members and the general public. Due to the number of possible attendees, we will use the Waiting Room. This means when you login into Zoom you will not be taken directly to the meeting. The waiting room will be opened at 7:00 PM. Prior to the meeting start time (7:30 PM) you may socialize with others in the waiting room. The meeting room has a capacity of 100 people.

For the Q&A session, you may ask your question using chat or may unmute yourself and ask your question directly to the speaker. To address background noise issues, we are going to follow the rules in the table below regarding audio. If you are not speaking, please remember to mute yourself. You are encouraged, but not required to turn your video on.

Meeting EventParticipant Can Speak?Participant Can Self-Unmute?
Director Rex’s General RemarksYesYes
Program Chair Victor’s  Speaker IntroductionYesYes
Speaker PresentationNoNo
Q&A SessionStart All on MuteYes                                    
5-minute bio break YesYes
Journal Club presentationStart All on MuteNo
Business MeetingStart All on MuteYes
Director’s closing remarksNoNo
Only the Business part of the meeting will be locked.

Featured Speaker: Stevenson Professor of Astrophysics at Vanderbilt  University, Keivan Stassun will give a presentation entitled, The Royal Road: Eclipses and Transits in the Era of Gaia and TESS.

In 1992, the first exoplanets were discovered by measuring the slight timing variations in rotating pulsars. Since then, we’ve pointed increasingly sophisticated ground- and space-based instruments at more normal stars, hoping to image their planets directly, or to see the stars blink, wobble, or lens in ways that reveal orbiting companions. The current tally of exoplanets tops out at about 4,400-and very much still counting. Out of the many hot Jupiters and mini Neptunes we’ve also spotted rocky planets, a few mirroring Earth in size, density, and habitability. Prof. Stassun will discuss the ways in which eclipses and transits of stars by their companions – utilizing light curves from the NASA TESS mission and parallaxes from the Gaia satellite – can be used to determine the fundamental properties of stars and characteristics of their planets by the thousands, and with a precision never before possible.

Prof. Keivan Stassun is the Stevenson Professor of Physics and Astronomy at Vanderbilt University. He earned undergraduate degrees in physics and astronomy from UC Berkeley and a PhD in astrophysics from the University of Wisconsin. Prof. Stassun was a NASA Hubble postdoctoral fellow before joining the Vanderbilt faculty in 2003. Prof. Stassun’s research on stars and exoplanets has appeared in more than 350 peer-reviewed journal articles. He is a co-investigator for the NASA Transiting Exoplanet Survey Satellite (TESS) mission, and is the founding director of the Vanderbilt Initiative in Data-Intensive Astrophysics, through which his group participates in the Sloan Digital Sky Survey and other large-scale collaborations. Prof. Stassun is an elected Fellow of the American Physical Society, the American Astronomical Society, and the American Association for the Advancement of Science. He has received recognition for his scholarship and teaching, including a CAREER award from the National Science Foundation, the Cottrell Scholar Award from the Research Corporation for Science Advancement, and was recently named Mentor of the Year by the AAAS.

Prof. Stassun is a national leader in initiatives promoting diversity in astronomy and space science. The Fisk-Vanderbilt Masters-to-PhD Bridge Program, which he founded, has become one of the nation’s top producers of PhDs to underrepresented minorities in the physical sciences. He has served on the NSF Committee for Equal Opportunity in Science and Engineering, and is a recipient of the American Physical Society’s Nicholson Medal for Human Outreach.

Prof. Stassun recently launched the Frist Center for Autism and Innovation, focused on advancing science and engineering through the engagement and advancement of individuals with autism. Prof. Stassun’s autism activism became newsworthy late last year when the CBS News program “60 Minutes” highlighted his recruitment of Dan Burger, a data scientist on the autism spectrum, to help make sense of the massive amounts of data coming from the Kepler space telescope. Making a virtue of his unique talents to discern patterns in data, Mr. Burger invented a software tool that produced a new way of judging the sizes and ages of stars based on how vigorously they flicker in the night sky.

Prof. Stassun is the author and presenter of a course for The Learning Company, “The Life and Death of Stars,” a visual and intellectual feast describing the life cycles of stars and their evolution within stellar nurseries.

March’s Journal Club Presentation: Surabhi Agarwal will speak on her visit to Jantar Mantar Observatory in India. She will talk about the history of these masonry instruments.

AAAP webcast:  This month’s AAAP meeting, beginning with Rex’s opening remarks and ending at the break before the business meeting, will be webcast live on YouTube and recorded for subsequent public access on AAAP’s YouTube channel. Be aware that your interactions during this segment, including questions to our guest speaker, may be recorded for posterity. Here is YouTube live link

Using Zoom: While we are, social distancing the AAAP Board has chosen to use Zoom for our meetings, based our belief that many members have already have used Zoom and its ease of learning. One of its great features is you can choose whether you want to install the software on your computer or use it within your browser.

How to Join the March Meeting: For the meeting, we are going to follow a simple two-step process:

  1. Please make sure you have Zoom installed on your computer. You do not need a Zoom account or need to create one to join the meeting. Nor are you required to use a webcam.
  2. Please visit our website for the link to the meeting
  3. This session will be recorded and saved on YouTube. Send me an email at if you have any concerns.

NOTE: We plan to open the meeting site 30 minutes to the 7:30 start time. This way you won’t have to rush to join the meeting. A maximum of 100 attendees can join the meeting.

More Information: The Zoom site has many training videos most are for people who are hosting a meeting. If you’re unsure how Zoom works you might want to view the videos on how to join a meeting or how to check your computer’s audio and video before the meeting.

We hope to make these short presentations a regular feature of our monthly meetings. If you are interested in presenting a topic of interest, please contact either or We’d like to keep our momentum going!

Upcoming Programs: Here’s a look ahead at upcoming guest speakers. We’re expecting to conduct virtual meetings for the remainder of this academic year. In an effort to turn necessity into a virtue, we’re casting our recruiting net a bit wider than usual, inviting speakers for whom a visit to Princeton would be impractical or inconvenient. Suggestions for guest speakers for September, 2021 and beyond are welcome.

April 13 – Alexandra Kroll Davatzes: Prof. Davatzes is an Associate Professor at Temple University. Her talk will describe Precambrian Meteor Impacts and Implications for Early Earth.

May 11 – Alex Hayes: Prof. Hayes is an Associate Professor of Astronomy at Cornell University and Director of its Spacecraft Planetary Image Facility. He will speak on Ocean Worlds of the Outer Solar System, plus he will give a brief report on the Mars 2020 mission.

June 8 – Anna Schauer: Dr. Schauer, a new mother, is the NASA Hubble Fellow at the University of Texas at Austin. She leads the team researching what she’s nicknamed the Ultimately Large Telescope, a lunar liquid-mirror telescope that will aim at investigating First Star Formation.

Looking forward to you joining us on Zoom or YouTube Live webcast at the March meeting!

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Minutes of the February 9, 2021 General Meeting (Online)

by John Miller, Secretary

The meeting convened at 7:30 PM via Zoom.

●  Rex Parker announced the Washington Crossing State Park gave permission to proceed   with the WC Observatory support columns repair. 

●  The monthly Member Meeting is now being streamed to Yahoo, for real-time and archived viewing, initialized by Ira Polans and David Skitt.

●  R. Parker displayed various astrophotos: H II star-forming regions within and outside the Milky Way Galaxy.

●  The evening’s guest speaker, Princeton University’s Guðmundur Stefánsson, Ph.D., was introduced by Program Chair Victor Davis.  Stefansson’s presentation was titled:  Searching for New Worlds with Next-generation Astronomical Instruments.  Initially, there were approximately 55 attendees. The talk was well received.

●  About 9 P.M., the Journal Club presentation was made by member Ira Polans.  Titled: “Johannes Kepler, Parallax, and the Astronomical Unit”, the book describes how Kepler and his contemporaries measured the size of the Solar System.

Business Meeting:

●  Assistant Director Larry Kane reviewed his observatory repair fundraising efforts.  Treasurer Michael Mitrano reported these fundraising contributions from AAAP members have currently totaled about $4,000+. 

●  David Skitt reviewed the club’s membership to the Night Sky Network (NASA) and how it can benefit individuals at the AAAP.

●  Dave also had a Zoom meeting with a member of the public wanting advice on buying a telescope. This was followed by statements from several members who were also approached to give advice on the same subject.

●  Dave and Tom Swords discussed the purchase of “Bahtinov masks” to aid in the focusing of telescopes and cameras..

●  The Zoom meeting adjourned at 10:00PM

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How Did Hastings Design Our Objective? Part Two

by John Church

Objectives for smaller telescopes are sometimes designed to conform to the “Herschel condition” proposed by John Herschel in two papers in the early 1820’s.  These objectives perform well at nearby distances as well as on celestial objects at infinity in restricted fields of view. They don’t, however, completely satisfy Abbe’s 1873 sine condition for zero coma, although they usually show very little of this particular aberration.  

Hastings wrote that our present lens resembled a Herschel in design, but he didn’t reveal his actual calculations.  I find that at 5614 A., near the middle of the visible spectrum, A. E. Conrady’s quantity known as “offense against the sine condition” (OSC) is – 0.00026 for our lens: this is small, but not zero.  When scaled to the size of our lens, I find an OSC value of + 0.00022 for one purposely-designed Herschel lens (Boutry, “Instrumental Optics” p. 143) at 5460 angstroms, also near the middle of the spectrum.  These values are far below Conrady’s maximum tolerance of  +/–  0.0025 for a visual teslescope.

Objectives can be designed to show OSC values of +/- 0.00001 or even less.  The formula set that I gave in Sky & Telescope for November 1984 (based on the 18th-century work of Clairaut and d’Alembert as adapted in 1887 by C. Moser) does this quickly.  The spot diagrams in my January talk show that coma for our lens is indeed very small, even as far as half a degree off-axis (full field one degree, or about two moon diameters).

Hastings concentrated on correcting spherical aberration, and he succeeded with this in all his work.  He was also an early supporter of making the minimum focus at the middle and brightest part of the visible spectrum near 5600 A. instead of at the usual longer wavelength of the sodium D2 line at 5890 A.  He did this in the form of our 1879 lens and a 4-inch flint-in-front predecessor, as well as with larger objectives made later.

I’ve recently been able to “deconstruct” Herschel’s design procedures as published in an Edinburgh scientific journal in 1822.  This wasn’t easy due to Herschel’s use of an algebraic sign convention differing from the one used today, and his numerical tables required nonlinear interpolation. My provisional conclusion is that our 1879 lens isn’t a Herschel type.  Neither did Hastings use the older and better methods of Clairaut and d’Alembert.  Whatever particular method Hastings did use, it still resulted in an excellent lens.

After the weather gets better, I intend to make some simple empirical tests to see how our lens works on objects 50 to 75 feet away. According to Conrady, Fraunhofer made such tests in the halls of his workshop at the Benediktbeuern cloister in Bavaria.  If so, then he might have been making Herschel-type objectives, consciously or otherwise.  After March 1821 he would likely have known about Herschel’s published work.

Interestingly, as shown 12 years after making our lens, Hastings by then had become less of an admirer of Herschel’s design methods (Sidereal Messenger Vol. X, 1891, p. 315).  This was part of a long essay on the history of telescopes delivered as an address at the dedication of the Goodsell Observatory at Carleton College in June of 1891.  At this period Hastings was a consultant to Brashear and had designed the 16.2-inch lens of Carleton’s new telescope.

Herschel did visit Benediktbeuern in 1824 (Fraunhofer died in 1826).  Herschel had hoped to learn more about Fraunhofer’s secret methods of making exceptionally fine optical glass, but in this he was disappointed  (Myles Jackson, “Spectrum of Belief”, MIT Press, 2000).

Speaking of Fraunhofer, it’s odd  that he seems to have been unaware of the 1760’s work of Clairaut and d’Alembert on fully correcting coma.  Fraunhofer left so few written records that we’ll probably never know if he did or not.  In support of his not knowing is the fact that at least some of his finest products do have a small amount of coma, as mentioned in my 1984 article.

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“Sky at Night” on Mars from the BBC

by Richard Sherman

Late last year, I subscribed to the BBC’s Sky at Night magazine, which is available in the USA in both print and digital editions. There is a 2-for-1 sale ongoing now where you can get two years for the price of one. Personally, I prefer it to Sky & Telescope because it has more articles and arguably better images. In the February 2021 edition, they write about what we would see of the heavens if we lived on Mars.

“On Mars, thanks to the dusty atmosphere, you would see a sunset dyed purple and blue, with the faraway Sun reduced to a shrunken blue coin before it set…. Depending on the time of year, you might also see…Earth, a strikingly bright spark of silvery blue, which at its best would blaze brighter than magnitude -2.5. If Earth was showing a full or gibbous phase, through your telescope you would clearly see its familiar green continents and blue oceans on the dayside, and the lights of its cities glinting on the nightside. And just imagine what an incredible sight a crescent Earth would be through your highest-powered eyepiece…. However you set up you telescope a problem would quickly present itself: Mars has no ‘North Star’ like Polaris here on Earth, to align….”  

And then regarding the moon(s):

“Our Moon crawls relatively slowly across the heaven. In contrast, Mars’s two moons, Phobos and Deimos, move far more rapidly across the sky. To the naked eye Phobos would resemble a pebble one third as wide as Earth’s moon, while Deimos would appear more like a bright star. But both would shine brightly enough to cast your shadow on the rocks…”

The article, entitled “The Red Planet’s Sky at Night,” is available online for free—the magazine allows non-subscribers three (3) free articles per month. Here is the link to the full article: What does the night sky look like on Mars? – skyatnightmagazine

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