Centre for Astronomy, University of Western Sydney

:)


Download 145.86 Kb.
Page1/5
Date conversion12.03.2017
Size145.86 Kb.
  1   2   3   4   5
The U.S. Naval Academy Observatory Programs and Times Gone By: A Tale of Two Domes

by CDR Paul D. Shankland, 906 Murray Road, Naval Air Station, Meridian, Mississippi 39305, Darkskies38@hotmail.com

In fulfillment of the Research Requirement for Topics In The History Of Astronomy (54111) 2001 Semester Two

Centre for Astronomy, University of Western Sydney

© 7 December 2001. Revised 02/01/02.

ABSTRACT

In this treatise I will explore the origins and evolution of the college observatories found at the U.S. Naval Academy at Annapolis, Maryland, from the Academy’s 1845 foundation, to the present day. Seamanship and celestial pursuits have perennially kept each other’s company, and here is no exception, with astronomy taught within the mathematics, then physics departments, with varying associations to the venerable Naval Observatory all along. This examination will reveal that permanent observatories at USNA belong to two diverse eras: the nineteenth century (recently reclaimed), and modern times. While celestial navigation and astronomy were taught in between, they did not benefit from a permanent observatory; the Navy relied on USNO for its celestial prowess. Observational astronomy (primarily celestial instruction) began with the original observatory erected shortly after USNA’s founding, and while some physics research began during Nobel laureate Albert Michelson’s tenure, observatory research remained on the periphery - more so with the dome’s razing in 1908 (although evidence suggests plans had been to replace the dome with one atop Mahan Hall). A replacement observatory finally made its debut in 1968, atop newly-erected Michelson Hall, while another ‘vintage near-restoration’ came about in 1991. This dome, whose rebirth is an interesting tale, houses the rediscovered Alvan Clark 7.75-inch (19.7-cm) optics. Michelson Hall’s dome originally housed a 0.41 meter catadioptric, replaced by a 0.51 meter in 1994.

I visited “The Yard” to speak with faculty about the observatories, and toured the equipment with pleasure, some two decades since my involvement as a student. The resultant research as discussed here will reveal my findings, in four elements, discussing: key observatory personnel, the observatory telescopes and instrumentation at USNA, research programs specifically involving these observatories, and the school’s educational activities relating to the two domes there then, and now.
LIST OF CONTENTS

Title Page

Abstract

List of Contents

1 Introduction

2 USNA’s Beginnings In Celestial Study

2.1 Academy Beginnings

2.2 Observatory Built

3 The Original Observatory and 19.7 cm Clark

3.1 The Clark Telescope

3.2 Other Observatory Instrumentation

3.3 The Observatory, Pictorial Perspective

4 Education And Educators At The Old Observatory

4.1 What 19th Century Mids were Taught

4.2 Role of the Professors of Math, U.S.N.

5 Michelson, Science-For-Science In Physics, The Demise

5.1 Michelson

5.2 End of the First Observatory and What Taught Then?

5.3 Were there Plans for Mahan Hall?

6 The Academy and USNO – Close Ties

6.1 Similar Science Paradigms

6.2 Solar Eclipse of 1869

6.3 Today’s Relationship – Finding the Refractor

7 Michelson Hall’s Observatory: 0.41 Meter

7.1 Overcrowding Leads to New Hall

7.2 Naval Academy Again Gets an Observatory

7.3 The Original Reflector

8 The New 0.51 Meter: Today’s Instrumentation

8.1 Renovation and Growth in 1994

8.2 Midshipmen in the Robotics Biz

9 Return of Venerable Optics: 19.7 cm Refractor

9.1 Lost and Found

9.2 Seeking a Home on the Yard Again

9.3 The Class of 1941 and a New Dome

9.4 Details of the New Instrument for Old Glass

9.5 Curiosities about the Clark Achromat

10 Observatory and Faculty today

10.1 The Physics Department

10.2 The Astronomers

10.3 Professors: Teaching vs Research

11 Research Alive and Well Today

11.1 The Midshipmen

11.1.1 Trident Program

11.1.2 Another Former Midshipmen doing Famous Things

11.1.3 Near Earth Asteroids

11.2 The Professors

11.2.1 Radio Astronomy

11.2.2 Galactic Jets, Tomographic Methods

12 Modern Education at the Yard’s Domes

12.1 The Classes

12.2 The Astronomy Club

12.3 Community

12.4 Small Radio Telescope In the Works

13 Discussion

14 Conclusion

15 Acknowledgements

16 Bibliography
The U.S. Naval Academy Observatory Programs and Times Gone By: A Tale of Two Domes
1 INTRODUCTION

Seafaring means navigation, and throughout mankind’s existence, when a mariner set sail upon the high seas, his navigational method to reach ports in distant lands primarily focused on where he was in relation to the heavens above. So it is not surprising that, when the U.S. Naval Academy (USNA) was founded in 1845 in Annapolis, Mary-land, construction of an astronomical observatory followed short suit. While its educational focus aimed primarily at celestial navigation and timekeeping, there nonetheless existed an early forum by which to introduce the rudiments of astronomy to midshipmen. Originally a part of the mathematics department -- indeed, taught mostly by intriguingly designated “Professors of Mathematics, USN” -- the Naval Academy sought to emulate its “elder brother”, the esteemed US Naval Observatory, with USNO providing its more practical paradigm of ‘application’. Eventually the Naval Academy broadened its scope to include a more purist fare, and research was carried out in the Yard (notably by the likes of then-fledgling Albert Michelson) – but not in observational astronomy until the late twentieth century. However, as solar astrophysics gained an American footing in the late nineteenth century, the Naval Academy was able to carve a small piece of historical pie for itself by providing its primary observatory instrument for USNO use on a solar eclipse expedition in 1869. As would be expected, the observational research aspects did not dominate the original astronomy program, and in fact, the observatory lost its stand to demolition crews (in 1908; some documentation – incorrectly – recounts demolition in 1907) carrying out Admiral Porter’s wholesale renovation plan, a Flagg/Thompson design of 1895 to improve an otherwise meager campus. Ironically, an observatory was not included (apart from plans suggesting otherwise, to be considered later).

While celestial navigation and textbook astronomy continued to be an educational product at USNA, a permanent observatory program did not return per se, until the construction of Michelson Hall in 1968 (the first to be done in over half a century). Research discussed herein reveals a fascinating implication that Mahan Hall may itself have been the target of observatory plans as the Porter renovation began. With a modern Michelson Hall, its rooftop dome housing a 0.41 meter Cassegrain, a broader observational pedagogy returned to the Yard -- and as well, a more purist undergraduate academic environment took real root. Of late (1994) the Academy upgraded Michelson’s main instrument to a 0.51 meter Cassegrain, and midshipmen have made it a sophisticated, robotic affair, capable of Trident scholarship research. Trident scholars are those promising midshipmen who are allowed to do a senior research project in lieu of several majors courses; this, too, will be covered. In fact, the physics department has performed a wide range of research by both students and by professors, sometimes in concert with peer universities, sometimes with institutions such as the Naval Research Laboratory, although this was not the original practice. The infusion of “astronomy you can put your hands on” has broadened interest in the subject, and even stirred a USNA Astronomy Club to life to supplement the traditional gamut of academic offerings.

In 1986 this very club took a field trip to USNO in nearby Washington, D.C., and spied a crate in the Naval Observatory basement, marked “Naval Academy”…. Could it be? What was this, the original instrument’s optics? Indeed it was, as suspected as far back as 1975 in discourse between the USNA Museum and USNO. What followed was an intriguing tale to secure the venerable if not rare 7.75 inch (19.7 cm) Alvin Clark achromat for restoration and use in the Yard once again. In 1991 the newly-housed, still-esteemed objective saw first light from a dome funded by alumni from the class of 1941, set in a telescope, mount, and dome carefully designed for modern utility, yet original “feel” and look. This instrument is used by astronomy classes again and even more so by the club.
The story of observational astronomy at Annapolis thus takes two paths for our discussion: one, a chronicle of the original dome, and its eventual restoration at the Academy, and two, of the more research-oriented observatory atop Michelson Hall. We will look at both, compare and contrast what is a synergistic and enthusiastically-run program, well designed to educate the undergraduate who will one day pilot his ship or his jet out upon the high seas; and further, to hone sharp thinking with chaste intellectual observation so fundamental to the pure sciences. USNA continues to evolve geometrically in academic 'depth'. The latest research uses the .51-meter in a multi-year near-earth object (NEO) study to support Minor Planet Center endeavors (to include collaborative parallax studies). The most recent plans include purchase of a small L-band radio telescope; as well, a visual spectroscope purchase for extragalactic work. Indeed, research depth is a perennial issue at USNA; depth (and enough time) to conduct cutting edge, multi-year research poses a real challenge for an institution bent on academic excellence -- while training officers to lead at sea. Regardless, today’s midshipman receives an outstanding undergraduate education because for one, every resource is devoted to small undergraduate classes. Yet most of all, the Academy makes every one of its leading professors accessible to every student while also providing top quality, hands-on equipment not often seen at the undergraduate level. The road to such teaching methods -- especially for astronomy at USNA -- is rooted in the school’s very inception nearly two centuries ago. The observatories discussed here manifest the growth of the academic bent in the Yard, while perpetuating the nobler of seagoing traditions. To be sure, this is a tale of a blended old and new, of tradition and technology, of technical training versus unadulterated academia. It is a story of the maturation of a noteworthy piece of American astronomical history. It is undeniably a “tale of two domes”.

2 USNA’S BEGINNINGS IN CELESTIAL STUDY

Much of the Yard is steeped in tradition, and we find this especially so surrounding the early development of astronomy there. The observatory was erected very soon after Academy’s own founding, so that a brief recount of the Academy’s founding is in order -- that one might understand the character of those groundbreaking times. What follow are a synopsis and then a discussion of how and when the first Naval Academy observatory was erected.


2.1 Academy Beginnings

The Naval Academy’s founding is affixed to 1845, becoming fully collegiate (expanding from a two to four year program) by 1850. The impetus to create such an institution is an interesting one, and began some years earlier. The seeds were planted with the birth of the U.S. Navy in the Revolutionary War, and the need was further articulated by President John Quincy Adams in 1825; it was again underscored in 1842 by US Secretary of the Navy A. P. Upshur. Yet it took an incident of attempted mutiny aboard a naval training vessel to have naval leadership reconsider the wisdom of immediate on-the-job training for future naval officers. The incident occurred on the American Brig Somers in 1842, orchestrated by a midshipman named Philip Spencer; courts-martial and three hangings at the yard-arm ensued.

In response to this near-mutinous training travesty, succeeding Secretary of the Navy George Bancroft sought a schoolhouse to formalize the educational process, settling on a ‘cramming’ school called the Philadelphia Naval Asylum. In 1845 he moved it to the “healthy and secluded location of Annapolis to rescue midshipmen from the temptations and distractions that necessarily connect with a large and populous city”, and set up a school with 50 students and seven professors (King et al., 1995). The “Naval School at Fort Severn” in Annapolis was renamed the Naval Academy in 1850; and while accreditation and conferred degrees did not begin until much later (1937), serious academic studies did. This included astronomy classes from the start in what archival documents clearly identify as astronomy (Phythian, 1869) in 1845 under the Math Department, and was formalized in 1853 with the creation of the Department of Astronomy, Navigation, and Surveying.

Not eight years after USNA’s founding, ground broke for the Academy’s first actual observatory, with the now-venerated refractor finding its home there and operating by 1857 (Bell, 2001). The Department of Astronomy, Navigation and Surveying was first headed by now-honored mathematics professor William Chauvenet, followed by Professor Coffin, then LCDR R.L. Phythian. Before that astronomy was taught in the Mathematics department, also under Chauvenet. From 1853-1865 the requirement was to have a “professor of mathematics, USN” to teach this subject (see section 4). Typically three line officers and a civilian professor worked there. Conversely, the Physics Department was not formed until 1895 per se, but a precursor, the Department of Natural and Experimental Philosophy, was instituted from the start in 1845 and from here midshipmen studied various physical sciences. In fact midshipman-then-professor Albert Michelson’s famed work took place in this department. What makes this relevant is which department (and under what paradigm) astronomy fell at the time. While purist research and provocative thinking appears to begin during Michelson’s tenure, astronomy education itself was more structured, somewhat rote and practical. After all, it was taught to familiarize future naval officers with celestial navigation, as opposed to science for science’s sake. That tack would not take place for astronomy until a full century passed, and this mindset thus influenced the construction, then demolition, of the Academy’s observatories.

It should be noted that the neighboring U.S. Naval Observatory’s influences over Naval Academy astronomy are peripheral, but really cannot be denied. USNO set(s) the tone for navigationally-based, positional astronomy in the United States. Indeed for nearly a century, USNO had a dominating and foundational influence over much of American astronomy (see Lewis, I., 1947). Other substantial readings explore the complex history at that venerable institution, but a few principle relationships are worth discussing here (and later, two specific collaborations will be deliberated upon). Firstly, USNO itself began shortly before the Academy in 1830, as the Depot of Charts and Instruments. As it became the ‘Naval Observatory’ at its Potomac River site in 1844, it had developed a cache of unprecedented instrumentation -- a world-class collection for that era. Also in 1848, a corps of professors of mathematics was shared between both USNA and USNO, though it was created primarily to fulfill a need to train its midshipmen. Following USNO’s lead, USNA’s approach to teaching astronomy also remained strictly positional throughout the 19th Century. Indeed, astronomy remained entirely separated from the Natural Philosophy, then Physics (and Chemistry) departments throughout the life of that observatory. Nor did navigation join seamanship, its present association/department until 1933 (M.A. Anderson, 1935).

2.2 Observatory Built

The first observatory building on the Yard found a central location near the west end of Stribling Row and was adjacent to the original chapel. Spencer Baird (1879) of the Smithsonian reports the precise location east of Washington, D.C. by 0h 2m 15.91s (unusual annotation, the exact reference meridian is unclear), at latitude North 38º58’53.5” which is midway between today’s chapel and Chauvenet Hall.. Begun during CDR Stribling’s superintendence on 1 July of 1850, the building was finished a year after the astronomy department was established, in 1854 on November 1st; the main objective was then completed in 1855, and the observatory was reported to be operational with the telescope in place by 1857. It cost $4696.75 to build (Lull, 1869). By comparison, the Chapel cost $3292.86 and the entire Academy budget in 1853 was $48,044.22, per Todorich (1984). Its dimensions were 31 x 16-feet, with 9ft x 15-foot extensions to each side as small wings, which housed a number of instruments aside from the primary refractor. The building formed the shape of a cross. It (along with several buildings built during Stribling’s tenure), was apparently built with inferior materials, so that the wall of one neighboring building spontaneously fell one night as midshipmen studied. Recitations were sometimes held in the left wing, while additional instrumentation was held in the right.

As well, there is some speculation that the academy’s unusual wooden cylindrical “turret dome” (not hemi-spherical) was attributed to an architectural design prototyped at the 1830’s-constructed Hopkins Observatory at Williams College. William Milham’s treatise on this observatory (1937) does not make such outright suggestion, although similarities are striking, and such speculation exists at USNA. Milham indicates there is some commonality of design for that era (and this was confirmed more recently by the author), but no other ties seem to exist. Albert Hopkins himself had a hand in the building of that observatory; those observatories were actually designed by completely different architects according to historian R. Ariail of the Antique Telescope Society (ATS). Further, public works documents at the Yard show no indication that one was built as some replication of the other. It thus appears that some generic influence of the times may have taken place times in the Academy dome design, but to date no direct correlation has been proven.

3 THE ORIGINAL OBSERVATORY AND 19.7 CM CLARK

The soul of the original observatory was of course the 7.75-inch (19.7 cm) achromatic refractor made by Alvan Clark of Boston (Cambridgeport). With a clear aperture of 7 ¾ inches and a focal length of 112 ¼ inches, this objective was the only known Clark lens of this exact size, and was manufactured early in Clark’s career (Warner and Ariail, 1995). The telescope and its companion instrumentation were among the prized educational accoutrements in the eyes of Academy leadership even then; to wit, as the Academy moved to Fort Adams in Rhode Island during the US Civil War, the Superintendent himself penned a letter to his fellow superintendent at USNO to implore that the Naval Observatory store these instruments for safekeeping (Letters, 1845-1865). Further description follows, and thereafter discussion will turn to other instruments at the Academy’s observatory.


3.1 The Clark Telescope

Often considered to be in the ‘8-inch class’, this rare lens was regarded then (and now) to be of exceptional quality and one of the few remaining Clark lenses from the 1850’s. When the lens was rediscovered (see section 9 below), its quality was tested by Muffoletto Optical Company using modern methods; The Muffoletto team described it to be ‘good with beautiful spherical bands’. Historian Bob Hambleton (also of ATS) also indicated that this test had some good results.

Conversely, Consultant Barry Greiner inspected the achromat to initially have good correction for spherical aberration but severe astigmatism persisted; this was caused primarily by irregularities in the cell spacers, that vary in thickness from .003-inches to .141-inche, as tested in double-pass autocollimation. This curiously contrasts the original testing by Muffoletto, which does not discuss the spacer issue. Additionally, both elements containing many bubbles and flakes; which is not wholly unusual in the glass of the time. These flaws do not detract from the overall performance because lenses were artfully matched sets. Clark approached lens-making in a holistic, almost aesthetic manner, his hands reportedly often gauging excellence merely by feel. Modern, anecdotal evidence suggests this mythical ability attributed to the Clarks is perhaps wishful thinking. Nonetheless, Clark’s revered lens-making techniques as disclosed in Warner and Ariail’s account describe Crowns and flints matched as unique, optimized pairs. It is the author’s belief that defects noted by modern methods are of little consequence as compared to the ‘net effect’ of an objective brought together by Alvan Clark, offsetting errors; personal observation of the achromat’s quality by the author suggests a fine net optical effect. Confidence was enough that Clark and Sons signed this objective, not a common thing, indicating a highly regarded hand at its fabrication, and the company willingness to stake its reputation on the objective’s excellence. Hambleton believes the actual glass pusher for the 7.75-inch may be Robert Lundin, incidentally the last director of the Clark Works. This is a somewhat contentious and unresolved issue, as it is unclear whether Lundin was yet employed by the Clarks when the lens was fabricated. Discussions with Barry Greiner of D & G Optical, who also repaired the objective cell and made measurements of the glass in early November of 1990, feels as well that the craftsmanship found in this glass more likely reflects Alvan Clark’s own work, at least in the optical figuring. His personal observation of the flint-edge signature, signed “Alvan Clark Cambridge, Mass. 1855”, and the implied difficulty working this piece of glass (rejectable by today’s standards with at least four veins of internal striations, notable internal inhomogeneities, and a very thin edge, remarkably surmounted by the maker) leads him, along with ATS experts Bart Fried and Peter Abrahams to conclude it was unlikely Lundin’s work but the elder Clark’s. Indeed, the signatory etching is in Clark’s hand and is on the flint’s edge.

An old USNA report (Phythian, 1869) from that era also notes the telescope to be “one of the best in the state [of Maryland]”, and another modern optical assessment (by expert Paul Watson) declares it to be “very nice”. The laudatory comments of the past are really only of interest as documented commentary about the lens; one must recognize that the 7.75 inch had very few “competitors” with which to compare quality at that time. Empirical evidence was sought from that era as to resolution of double stars, but little further original documentation was found. The author’s opinion is that the lens is above reproach, while it remains unclear if it reached its half-arcsecond theoretical limit of resolution during its initial use in the 19th century. Suffice it to say that Watson and Greiner’s conflicting modern reports leave the enthusiast hungry for information on any original testing of this curious lens, to resolve this debate as to this lens’ original caliber - which may incidentally help gauge the level of performance generated by Clark in the 1850’s. Certainly, as verified by discussions with Fried and Greiner, the lens itself is of superb quality. Greiner noted the problem was in fact due to spacers and possibly pinching in the cell (which is hard to adjust for a thin-edged element), now corrected. See section 9 for more on the lens. Greiner’s test comments were based on spacers he found between the elements which were very irregular for a lens of Clark vintage, with spacer variations such as 4.1, 10, and 3.2 thousandths of an inch. Surely, these must not have been the original spacers, and must have been put in place after Clark’s time. The elements themselves are superb in quality, and now show no astigmatism with new, proper spacers.




  1   2   3   4   5
:)


The database is protected by copyright ©hestories.info 2017
send message

    Main page

:)