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Dr. John Church, via Zoom

The Fourth Condition: A Spyglass Drama.

January 12, 2021

7:30 p.m.



Amateur Astronomers Association of Princeton is inviting you to a scheduled Zoom meeting. This meeting is open to AAAP members and the public. Please mute yourself if not speaking. Limit 100 participants.

We are planning to make use of chat for the Q&A session and are planning on ways to reduce the background noise. To address background noise, we are going to follow the rules in the table below regarding the audio. If the background noise gets to loud during Q&A or the Business Meeting we will Mute All.

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Only the Business part of the meeting will be locked.

Featured Speaker: Longtime AAAP member John Church will give a talk entitled, The Fourth Condition: A Spyglass Drama. John’s presentation will summarize the steps leading up to the design of well-corrected doublet achromatic refractor objectives.

The starting point for such a design is to choose an aperture size and the desired focal length. Next to be considered are what kinds of glasses are available, how best to minimize secondary color, spherical aberration, and finally coma. These design methods date from the pioneering researches of Alexis Clairaut, Jean le Rond d’Alembert and others in the 18th century, since then adapted and republished by many others. Equations for implementing their design principles were converted into a BASIC program published in Sky & Telescope (November 1984; V. 68, No 5, pp. 450-1).

John will discuss the design and performance of AAAP’s historic Hastings-Byrne 6 ¼ inch refractor, with remarks about Charles Hastings, the maker of its objective lens. He will show lunar photographs taken with this instrument. For a bit of drama, John will describe the scientific rivalry between Clairaut and d’Alembert.

Speaker’s Biography: A native of Richmond, John Church graduated from the University of Virginia with a bachelor’s degree in chemistry and then earned M.S. and Ph.D. degrees from Lawrence University in Appleton, Wisconsin. His thesis work was concerned with the reaction of crystalline carbohydrate derivatives with oxygen under relatively mild conditions. He spent his career in research and development with American Can Company at their Corporate R&D laboratory in Princeton and then with Colgate-Palmolive at their Corporate Research Center in Piscataway.

John is the author of sixteen scientific, historical, and technical publications, including several on the optics of refracting telescopes as well as one on close conjunctions of Jupiter and Saturn. He holds ten U.S. patents and is the author of a book chapter on the chemistry of bleach. He has written three books and edited several others. One of his Sky & Telescope articles traced the history of the 6 ¼ inch Hastings-Byrne refractor now installed in our observatory in Washington Crossing State Park, which he and many others helped build in the late 1970s.

John has served as Assistant Director, Director, and Program Chair of the AAAP. Next year will mark his 50th year as a club member. His civic activities include presently serving on the West Windsor Township Zoning Board of Adjustment. He is married and has three children and six grandchildren.

Using Zoom: While we are, social distancing AAAP has chosen to use Zoom based our belief that many have already used it 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 January 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. The link to the meeting is --
  https://zoom.us/j/91627586392?pwd=clVqZkZWdjgzNTlPMjNWcEF1b2FLZz09

  Meeting ID: 916 2758 6392
  Passcode: 184279

NOTE: The meeting room will open at 7:00 PM. You will be placed in the waiting room until the speaker has joined us. If you do not have Zoom installed on your computer. tablet, or phone, it will be automatically installed when your join the meeting unless you choose the browser option.

If you click on the meeting link and it doesn’t work, simply copy and paste it into your browser.

More Information on Zoom: 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.

January's Journal Club Presentation: Bob Vanderbei will kick off the new year’s Journal Club presentations by showing some of his excellent and timely astrophotos and explaining how he accomplished them. In addition, Bill Murray will tell the story of Project Diana, in which a small local team of radar experts first probed a celestial body by bouncing radio pulses off the moon, 75 years plus two days ago.

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 director@princetonastronomy.org or program@princetonastronomy.org. 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.


February 9
Guömundur Kári Stefánsson

Dr. Stefánsson is the Henry Norris Russell Fellow in Princeton’s Department of Astrophysical Sciences. He will speak on innovative techniques he has helped develop for Detecting and Characterizing Exoplanets.


March 9
Keivan Stassun

Prof. Stassun is the Stevenson Professor of Astrophysics at Vanderbilt University. He will describe The Life and Death of Stars, the title of a course he delivered for The Learning Company.


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 Mars2020 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.

End of an Era: For more than five years, we have all benefitted from Ira’s efforts in recruiting an impressive array of interesting guest speakers. Their expertise and scholarship, often on the cutting edge of astronomical research, are a defining characteristic of this club. Ira took on a vital role, and he did it very well. As they say in showbiz, he’s a tough act to follow. As Ira transitions from Program Chair to Active Member, I want to express my gratitude to him not only for his past contributions, but also for generously sharing his information, experience, and advice with his successor (i.e. me). Through his judgment and thoughtfulness, I am confident of a graceful and seamless transfer of power. Thanks also to Bill Thomas, who contributes research and advice to help identify topics and presenters. I’m thankful and relieved to have Bill’s and Ira’s help. Though I’m officially taking over as Program Chair, Ira will still be quite visible as Zoom maven, and of course as an active member of AAAP. He can be reached at ipolans@princetonastronomy.org. .

Looking forward to you joining us on Zoom at the January meeting!

Victor Davis,
Program Chair