Classes in celestial navigation and related topics

ReedNavigation -- located on Conanicut Island Most classes held at Mystic Seaport Museum


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Captain Richard D. Buchanan wrote: 11/12/2019
I have taken Frank's Modern Celestial Navigation class twice. I am always inspired and I always come away with a few practical techniques and more than a few insights into the history and beauty of celestial navigation. You owe it to yourself to enjoy this class, whether or not you are a mariner.
John Workman wrote: 11/20/2018
I just took one of Franks classes and it was awesome!!

Frank taught an incredible class on celestial navigation that brought me from novice to some solid understanding of sextants, their history and most importantly their use as a aid to seeing the sea...and knowing where you are on this planet!

Hands on, wealth of knowledge, great resources at Mystic Seaport, he really covered a lot of ground! There was a lot of math but unlike in my youth, I was on the edge of my seat to soak up knowledge!! Frank made it relatable and real. The sextant which is such an iconic tool of the sea, was demystified. By the end of class i felt comfortable with it. I had mastered how it worked, how to read it and how to adjust it to insure its accuracy.

I came away with all of the cheat sheets and understandings of equations and concepts that breathe the life into what you capture through your sextant sightings.

I would highly recommend Frank and believe the Mystic Seaport with its planetarium, an ideal setting for my class with him discovering this timeless tool of the sea.

Frank did a great job keeping the class interesting with visual aids, both on screen and out on the seaport grounds. Frank had also noticed i was interested in the Draken. This is the Viking ship which had made its voyage across the Atlantic and up and down the east coast, resting for winter in Mystic as the troops regroup, gathering resources for another ocean voyage. He took extra time to talk about and show with polarized film the concept of the "Viking Sun Stone" which is a suspected navigational aide the Vikings may have used to traverse the globe as they had.

All in all i would highly recommend this class to any and all folks interested in learning about navigation and sextants. Informative and digestible, but most of all useful to the point where i am comfortable with the instrument and have the formulas needed to continuing to set my sights on the horizon!!

I look forward to more classes to learn more from Frank and strengthen my understandings of celestial navigation!

Thank you!!!
Mark Coady wrote: 6/6/2017
I have now done every course I think that has been offered so far at Mystic Seaport taught by Frank Reed in the last two years. I found the courses to all be extremely rewarding.

Several things stand out. The course material is presented in a balanced way, with a well thought mixture of detailed calculation, broken up by historical, factual, and hands-on aspects. This type of teaching is well suited to most, as it provides periods of more intense reasoning with relaxation and humor. Anyone can walk away with new-found knowledge. I also feel that the approach of understanding historical context and a simple practical approach is unique. It has gone a great way toward clearing up a lot of my preconceived ideas and confusions resulting from the many contradictory or esoteric approaches found in various volumes or on the internet.

Very simply, I learned a lot and it went a long way toward clearing up a mess. I was fascinated the whole time. The courses and NavList provide the tools to keep learning even after the course is over. I left able to measure what I see with a more calibrated eye for real world application, and a greater appreciation of human history. I can strongly recommend these classes for the curious, the fascinated, the historian, the hardcore navigator, or the armchair one. There is something in them for all.

I also found the NavList community to be helpful and encouraging as my journey continues. I hope I can undertake even more material in additional courses in the future.

"There is nothing - absolutely nothing - half so much worth doing as simply messing about in boats" (Kenneth Grahame, from the "Wind in the Willows")

Capt. Mark

Frank Reed wrote: 6/6/2017
Mark, Thank you so much for attending so many classes, and thank you for your kind words!
Dr. Russell D. Sampson wrote: 6/22/2013
I took Frank's 19th Century Celestial Navigation class in April 2013 and really enjoyed it. Not only was the class interesting but my fellow classmates were too; a retired skipper of a ballistic missile sub, the son of the fellow who invented GPS, a teacher, a captain of a Panamax container ship and a fellow who crossed the Atlantic solo - twice!

The class was also a great resource for my teaching and my own research interests such as the visibility of celestial objects in the daytime (Jupiter and Venus) and the effects of astronomical refraction near the horizon. I hope to take more workshops with Frank.

Dr. Russell D. Sampson
Wickware Planetarium
Eastern Connecticut State University
Sarah Ilsley wrote: 6/22/2013
I also took Frank's 19th Century Celestial navigation class. The instruction was thorough and I learned much more than I expected. Not only the techniques of celestial navigation, but a rich account of it's history as well. We had plenty of time to practice using sextants ourselves, and Frank did his best to make sure that each of us understood what he was teaching. He really knows his stuff!!

Also, the class was made more enjoyable through discussions with my other classmates during, and after the class had ended! You know a class is worthwhile when the learning continues outside of the classroom.
Philip M. Sadler wrote: 6/22/2013
What a joyful and stimulating experience to enroll in Frank Reed's class, Celestial Navigation: 19th Century Methods. Frank is a skillful and engaging teacher, able to draw students into this fascinating subject, whether they be novice or experienced. His depth of knowledge is tremendous. Participants get a real taste of what it was like to be aboard a sailing ship of the day. I learned much to enliven my own teaching and decode 19th century ship's logs. It is a rare experience, indeed, to have so much thoughtfulness, enthusiasm, and fun packed into two days. This is the way to learn!

Philip M. Sadler, Ed.D.
F.W. Wright Senior Lecturer in Celestial Navigation
Harvard University Astronomy Department
Cambridge, MA
Amy Reifsnyder wrote: 6/22/2013
Thoroughly enjoyed the Celestial Nav class at Mystic Seaport. Very clear instruction, with patience and broad depth of understanding for all in attendance.
I highly recommend any of Frank's classes and workshops, since the guy knows what he's talking about, and he can explain it to folks with (or without) all kinds of math and physics backgrounds.

Plus, it's just plain fun to realize that all you have to do to find out where you are in the universe is "look up". Now that's just cool.
Samuel S. Caldwell MD wrote: 6/25/2013
I thoroughly enjoyed Frank's first class in celestial navigation held at Mystic Seaport, and hope to be back for more.

Samuel S. Caldwell MD
Saratoga Springs, NY
Andrew Seligman wrote: 9/16/2013
I took Franks basic class at Mystic seaport. Frank is a fantastic instructor. He made the noon-sight and polaris sight reduction really easy!
Bob Goethe wrote: 9/11/2014
We are considering using the planetarium in Edmonton as a place to teach celestial navigation, enjoying freedom from cloudy skies by actually teaching the mechanics of sextant use inside the planetarium theater itself.

I would appreciate talking to your people if you have done this, to discuss things like determining "dip" in a theater where the sextant user is actually BELOW the projected horizon rather than above a true horizon outside.

Another issue is that the altitude of a celestial object projected on the theater's dome would vary from one seat to another inside the theater. I would love to discuss how you have managed this.

Bob Goethe
Frank Reed wrote: 9/11/2014
Bob, while many aspects of celestial navigation and positional astronomy can be taught under the dome, taking sights with a sextant in a planetarium is a fantasy --a fantasy often rediscovered! The problem of "dome parallax" (the variation of altitudes from one location to another under the dome, which you mentioned) is insurmountable with a "normal" planetarium projection. Even something as simple as estimating the altitude of the north star by "fists" is hopeless.
Andrew Lilly wrote: 10/1/2014
Frank and Bob,

You both bring up a fantastic idea that has been approached and (to some extent) solved before. Specifically for the U.S. lunar space program at the Morehead planetarium in NC.


Frank: you excellently bring up dome parallax, but isn't there going to be at least one point, or small area (near center of dome sphere, focal point of the dome) where the parallax wouldn't be nearly as significant? I'd assume this may require a platform / scissor lift etc and might not always be practical, dependent on the type of star projection system in the planetarium selected. I'd also guess the use of a bubble horizon would be necessary too.

Like Bob, I am also very interested in this subject with a local planetarium interested in the subject, and it doesn't seem to have a well published solution ;)

Your collective thoughts? Are there any good resources available on the subject?


Frank Reed wrote: 10/5/2014
Andrew, even if you shoot sextant sights from the very center of the dome, the results are poor due to parallax. Work out what happens in a dome with a 30 foot radius, if you shift the location of the sextant by just two inches. You should find that a "star" at 45 degrees altitude shifts by more than 13 minutes of arc. For all but the most crude observations of altitudes, this is too much to be useful for any purposes. Planetariums are very helpful for teaching coordinate systems and motions of the stars, and of course they're great for teaching basic constellations. But they do not function as "virtual reality" projections of the sky --at least not of sufficient fidelity for practicing celestial navigation sights in any useful way that I have been able to discover. NOTE-- there were specialized planetariums with collimated star projection systems built as navigation trainers in the 1950s. These project some of the bright navigation stars from outside the dome --quite different from a common planetarium-- but that works.
Frank Reed wrote: 1/24/2015
You don't need to purchase a sextant in advance, but if you have one, yes, bring it along. If you would like to acquire a relatively inexpensive, functional sextant, I would suggest looking for a lightly-used Davis plastic sextant. These turn up fairly often on eBay for $100 or less. They're real sextants. You can cross an ocean with one. They're somewhat less accurate than a proper metal instrument, but it's not a major concern. And you can always upgrade later.
Tony Fletcher wrote: 12/8/2013
During Drakes voyage around the world 1577 to 1580 did he ever calculate his longitude ?
He observed a partial eclipse of the moon but did not record his
longitude . I calculate it to be 75west.
Some historians say he calculated it by lunars while at Point Reyes
again it is not recorded
your thoughts please
Frank Reed wrote: 12/8/2013
Hello Tony.

There were occasional attempts to determine longitude by early forms of lunar observations on many voyages before the development, in the late 18th century, of the proper methodology of "lunars". Unfortunately, in nearly every case that I have seen, the methods used in those earlier examples are highly flawed and nearly useless for longitude. I've never looked specifically at Drake's voyage, but I would be happy to discuss it further if you have any details.

To determine longitude by a "lunar-like" observation, two things are needed:
1) a specifically recorded event involving the Moon's position in the sky, for example, the measurement of an actual "lunar distance" (the exact angle between the Moon and Sun or a star), or an observation of an occultation of a star, or an observation of a specific and well-defined event in a lunar eclipse.
2) an observation for local time that is nearly coincident with the first observation (of the Moon's position). This can be any observation of the altitude of the Sun or a star so long as it is well away from the meridian. This observation determines, what we might call, "sundial time". Without this second observation, which was often poorly understood historically, the first observation is nearly useless. Longitude is proportional to the difference between this local "sundial time" and the absolute time provided by the observation of the Moon's position.

It's worth noting that lunar observations for mapping, as opposed to "live" navigation, did not require a Nautical Almanac or proper "lunar theory". If the observations above were taken and recorded competently, they could be converted into an accurate longitude after the voyage by comparing against similar observations made at nearly the same time back in England, or any other comparison location. Unfortunately, few experimenters in navigation seem to have understood this point historically. So instead we find navigators attempting to work out longitudes on-site using the very flawed lunar motion models available before the 1760s. This was usually hopeless, resulting in longitudes in error by 10 degrees or more. But when they did record their observations in detail, and so long as those observations met the criteria for the two types of time above, then it's possible to work out relatively accurate longitudes even today.

Your suggestion that Drake's longitude on some date could be found from lunar eclipse observations is certainly reasonable. Whether an accurate longitude can come out of that depends on whether we can reliably determine the specific eclipse event that was observed, and equally important, whether there was some attempt to determine accurate local time simultaneously. As for a lunar longitude near Point Reyes, this probably falls in the category of wishful thinking. A standard "lunar" (in the 18th/19th century sense) was simply impossible in the late 16th century.

Frank Reed
Conanicut Island USA
Tony Fletcher wrote: 12/10/2013
Thank you for your comments
Drakes observation of a partial eclipse of the moon was after he had passed through the Magellan passage into the Southern Ocean It was observed at " 6 o 'clock in the evening and lasted two hours. Golden Hind was in a very bad storm at the time and Drake had much to occupy himself with at the time . Subsequently using the NASA web sight to from the time of the eclipse at London it was at 2300 hence I arrived at Drake's longitude of 75W.
Bawlf in "Secret Voyage of Sir Francis Drake" claims based or unsupported evidence that Drake set up an point of position in the Point Reyes area . This has been hotly denied by other historians .
AS you say it is unlikely that astronomers in the 16th Century had the skills or equipment to carry out lunar observations even on land . Gallileo did not invent the telescope until thirty years after Drake's voyage .
I am a Master Mariner and have PhD in history and am very interested in pre Harrison navigation methodology . Besat Regards and a Happy Christmas Tony Fletcher
George Goldsteen wrote: 3/26/2014
Dear Mr. Reed,
I noted your comment to Tony Fletcher that using lunar distances to determine longitude prior to about 1760 led to errors in Longitude of 10 degrees or more. I am a retired mariner, hydrographer and lecturer in these fields. The latter in Tasmania, which, as a former Dutchie, made me interested in Abel Tasman's voyage of discovery in 1642/43.

I recently obtained a copy of his logbook. The authors modernised Tasman's Dutch to modern Dutch to facilitate understanding what he wrote. Assuming they did this correctly I am amazed by the accuracy of his longitudes, at least of those near the coast of Tasmania (I have not attempted to check his positions in other locations on his voyage).

He almost daily (depending on whether the skies were clear enough) enters in his log that he measured his latitude and longitude and compass error. On days when he could not observe he calculated his position by Dead Reckoning. He used a variety of expressions w.r.t. how he obtained his position. E.g. "at noon we had the altitude of 41 degrees 15 minutes, longitude 172 degrees 35 minutes, course made good East and sailed 40 miles." Note that his miles equal exactly 4 nautical miles.
In the introduction by the authors no mention is made of Tasman's navigational methods, except to say that he used the Meridian of Tenerife as his Zero Meridian. It lies 16d39m West of the Greenwich Meridian. I automatically assumed he used lunar distances, but of course he could not possibly use these every day for the simple reason of course that the Moon is not always visible during the day, whereas it is obvious from Tasman's log he always obtained noon positions and always had a longitude and no mention is ever made of obtaining a fix at night.

My question to you: Do you have any idea what method Tasman used to determine his position ?
Kind Regards,
George Goldsteen
Evangelos Kontos wrote: 11/4/2014
Hello! I would like to ask you what DR Lat and DR Lon means at Predicted Geocentric Lunar Distances? If I wanted lunar distances at Greenwich I would put 0.00 at DR Lon? And what about DR Lat? Thank you in advance!
Frank Reed wrote: 11/4/2014
Hello Evangelos Kontos,

The entries on the lunar distance prediction page for DR lat and lon only matter if you select "Visible at DR Only". This is just for planning purposes. For example, if you wanted to practice shooting lunars tonight, you would not be interested in cases that cannot be seen from your position. Otherwise, the lat and lon data have no effect since the calculated distances are "geocentric". You can experiment with a couple of cases and verify this. Thanks for your question!

Frank Reed

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