THE
TROUVELOT
ASTRONOMICAL DRAWINGS
MANUAL
BY
E. L. TROUVELOT,
FORMERLY CONNECTED WITH THE OBSERVATORY OF HARVARD COLLEGE; FELLOW OF THE
AMERICAN ACADEMY OF ARTS AND SCIENCES, AND MEMBER OF THE SELENO-GRAPHICAL
SOCIETY OF GREAT BRITAIN; IN CHARGE OF A
GOVERNMENT EXPEDITION TO OBSERVE THE
TOTAL SOLAR ECLIPSE OF 1878.
NEW YORK
CHARLES SCRIBNER'S SONS
1882
INTRODUCTION
During a study of the heavens, which has now been continued for morethan fifteen years, I have made a large number of observationspertaining to physical astronomy, together with many original drawingsrepresenting the most interesting celestial objects and phenomena.
With a view to making these observations more generally useful, I wasled, some years ago, to prepare, from this collection of drawings, aseries of astronomical pictures, which were intended to represent thecelestial phenomena as they appear to a trained eye and to anexperienced draughtsman through the great modern telescopes, providedwith the most delicate instrumental appliances. Over two years werespent in the preparation of this series, which consisted of a number oflarge drawings executed in pastel. In 1876, these drawings weredisplayed at the United States Centennial Exhibition at Philadelphia,forming a part of the Massachusetts exhibit, in the Department ofEducation and Science.
The drawings forming the present series comprise only a part of thoseexhibited at Philadelphia; but, although fewer in number, they are quitesufficient to illustrate the principal classes of celestial objects andphenomena.
While my aim in this work has been to combine scrupulous fidelity andaccuracy in the details, I have also endeavored to preserve the naturalelegance and the delicate outlines peculiar to the objects depicted; butin this, only a little more than a suggestion is possible, since nohuman skill can reproduce upon paper the majestic beauty and radiance ofthe celestial objects.
The plates were prepared under my supervision, from the original pasteldrawings, and great care has been taken to make the reproduction exact.
The instruments employed in the observations, and in the delineation ofthe heavenly bodies represented in the series, have varied in aperturefrom 6 to 26 inches, according to circumstances, and to the nature ofthe object to be studied. The great Washington refractor, kindly placedat my disposal by the late Admiral C. H. Davis, has contributed to thiswork, as has also the 26 inch telescope of the University of Virginia,while in the hands of its celebrated constructors, Alvan Clark & Sons.The spectroscope used was made by Alvan Clark & Sons. Attached to it isan excellent diffraction grating, by Mr. L. M. Rutherfurd, to whosekindness I am indebted for it.
Those unacquainted with the use of optical instruments generally supposethat all astronomical drawings are obtained by the photographic process,and are, therefore, comparatively easy to procure; but this is not true.Although photography renders valuable assistance to the astronomer inthe case of the Sun and Moon, as proved by the fine photographs of theseobjects taken by M. Janssen and Mr. Rutherfurd; yet, for other subjects,its products are in general so blurred and indistinct that no details ofany great value can be secured. A well-trained eye alone is capable ofseizing the delicate details of structure