By Peter Van De Kamp (auth.)
This is the newest attempt in a series of displays began in 1949 with a sequence of lectures on long-focus photographic astrometry given by way of the writer as Fulbright professor in Paris on the invitation via the overdue H. Mineur, at the moment Director of the Institut d' Astrophysique. those previous lectures have been released as a chain of evaluate articles in well known Astronomy (1951) and seemed either as Contributions de l'Institut d'Astrophysique, Serie A, No. eighty one and as reprint No. seventy five of Sproul Observatory. A extra complicated presenta tion was once given in 1963 in Stars and Stellar structures, which was once through ideas of Astrometry (1967, W. H. Freeman & Co.). in the course of the moment half 1974, back lower than Fulbright auspices, on the invitation of Pik Sin The, I lectured on the Astronomical Institute in Amster dam, via a quick path in May-June 1978 on the invitation of E. P. J. van den Heuvel. I gave a extra huge direction on the Institut d' As trophysique on the invitation of J. C. Pecker of the school de France and of J. Audouze, Director of the LA.P. either in Amsterdam and in Paris I had awarded occasional astrometric issues at a variety of occasions. the chance to lecture in France and in Holland has facilitated, prompted and enhanced the association and contents of the shows just about long-focus photographic astrometry.
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Additional resources for Stellar Paths: Photographic Astrometry with Long-Focus Instruments
1) and, vice versa: sin Lla x tan 0 sin 00 + Y cos 00 ' . ~ _ sin 00 + Y cos 00 sm u + x2 + y2 . 2) vI Here ao, 00 refer to the tangential point, a as 0 to the object S, while a = ao + Lla and 0 = 00 + Llo. 4) are useful in dealing with the positions of asteroids and comets where transformation from standard to equatorial coordinates, since the object moves rapidly from field to field, and spherical astrometry is required. do = y. da is the projection of the path in the x-coordinate measured in right ascension, and 0 is the declination.
The pulse generators give 2000 counts per milimeter which is one rotation of the screw. The counts are displayed visually and are recorded by a card punch. The measurement of a star image position is accomplished, as in the one-coordinate Grant machine, by superimposing an image density profile upon its mirror image on an oscilloscope screen. The profiles are superimposed on separate screens for each coordinate, under manual control of the screws by handwheels. By judicious settings of the scanning slit heights, width, and the oscilloscope electronics, well peaked profiles of the circular images can be formed for precise settings.
By comparing the reduced positions from two measurements on each of several hundred plates the error of one measurement of the Grant machine has been found to be approximately one-half the error of the photographic positional information of images in a stellar reference frame. Thus the maximum improvement possible in the present photographic technique by a perfect measuring machine should be only about 10 %. This limit would predict a 5 % decrease in probable error when 12 CHAPTER 2 the mean of two independent measurements is taken.