Author name code: babcock ADS astronomy entries on 2022-09-14 author:"Babcock, Horace W." ------------------------------------------------------------------------ Title: Zeeman effect in stellar spectra (Astrophysical Journal 1947) Authors: Babcock, H. W. Bibcode: 1993inas.book..358B Altcode: No abstract at ADS Title: The solar magnetograph (Astrophysical Journal 1953) Authors: Babcock, H. W. Bibcode: 1993inas.book..373B Altcode: No abstract at ADS Title: Adaptive Optics in Perspective Authors: Babcock, H. W. Bibcode: 1992AAS...180.5701B Altcode: 1992BAAS...24..821B No abstract at ADS Title: Optical Gyroscopes Applied to Telescopes Authors: Babcock, H. W. Bibcode: 1991PASP..103..468B Altcode: Optical gyroscopes mounted directly on a telescope can provide its precise angular coordinates referred to the fundamental inertial system. Tracking of a star can be accomplished by computing continually in real time its changing apparent place and by applying computer-generated corrections to the telescope to maintain coincidence between the output of the gyros and the apparent place of the star. This system circumvents mechanical imperfections of the mounting and drives of the telescope, thereby promising significant cost reduction as well as improved performance. Title: Optical Gyroscopes Applied to Telescopes Authors: Babcock, H. W. Bibcode: 1991BAAS...23R.977B Altcode: No abstract at ADS Title: Adaptive Optics Revisited Authors: Babcock, Horace W. Bibcode: 1990Sci...249..253B Altcode: From the earliest days and nights of telescopic astronomy, atmospheric turbulence has been a serious detriment to optical performance. The new technology of adaptive optics can overcome this problem by compensating for the wavefront distortion that results from turbulence. The result will be large gains in resolving power and limiting magnitude, closely approaching the theoretical limit. In other words, telescopic images will be very significantly sharpened. Rapid and accelerating progress is being made today by several groups. Adaptive optics, together with the closely related technology of active optics, seems certain to be utilized in large astronomical telescopes of the future. This may entail significant changes in telescope design. Title: Erratum: "Test for a magnetic field in the white dwarf 40 Eridani B" [Publ. Astron. Soc. Pac., Vol. 100, No. 633, p. 1299 - 1301 (1988)]. Authors: Babcock, H. W. Bibcode: 1989PASP..101..135B Altcode: No abstract at ADS Title: Test for a Magnetic Field in the White Dwarf 40 Eridani B Authors: Babcock, Horace W. Bibcode: 1988PASP..100.1299B Altcode: This paper is reproduced from Publ. Astron. Soc. Pac., Vol. 60, p. 368 - 370 (1948) to celebrate the centenary of the Publications. See also 126.086. Title: Preliminary Design of an 8-Meter Pneumatic Telescope Authors: Babcock, H. W. Bibcode: 1988ESOC...30...99B Altcode: 1988vltt.conf...99B; 1988vlti....1...99B No abstract at ADS Title: Carnegie Institution of Washington Southern Observatory site survey, 1963 - 68. Authors: Babcock, H. W.; Irwin, J. B. Bibcode: 1987iopo.conf...99B Altcode: The CARSO site-testing team investigated ten coastal mountains in Chile between 27°S and 31°S; extended quantitative measurements of the seeing were made on four of them. Data from 900 nights are presented. High-level seeing between 29°S and 30,5°S was uniformly good, averaging 0.8 arcsec. Excellent seeing (<0.55 arcsec) occurred 19% of the time. The selection of the 5-km-long Las Campanas ridge with its four summits was based not only on the quality of the seeing but on topography, logistics, and remoteness from artificial lights. Title: Diffraction gratings at the Mount Wilson Observatory Authors: Babcock, Horace W. Bibcode: 1986PhT....39g..34B Altcode: No abstract at ADS Title: Diffraction gratings at the Mount Wilson Observatory Authors: Babcock, Horace W. Bibcode: 1986VA.....29..153B Altcode: No abstract at ADS Title: Air-support concept for a large telescope Authors: Babcock, H. W. Bibcode: 1985ApOpt..24.1248B Altcode: The advantages that accrue to a large telescope mounting concept in which air pressure is used to support over 250 metric tons, in the case of a 7.5-m diameter primary mirror, are discussed. This air support concept obviates the conventional external dome and accomodates such comparatively long focal ratios as those in the f/3-4 range, thereby yielding a less limited field and superior optical figuring and collimation. The telescope is housed within a sphere, and manipulated from below in either an altazimuth or equatorial mode. The cost of a telescope of this design will compare favorably with other designs recently proposed in the literature. Title: Instrumentation - the Du-Pont Telescope - Anta-Barbara Computing Facility - Direct Image Tube Camera for Las-Campanas - Infrared Photometer for the Swope Telescope - Infrared Fabry-Perot Spectrometer - Prime-Focus Universal Extragalactic Instrument - Authors: Babcock, H.; Brucato, R.; Kennicutt, R.; Persson, S.; Mould, J.; Geballe, T.; Gunn, J.; Westphal, J. Bibcode: 1979haob.rept..777B Altcode: No abstract at ADS Title: Requirements for ground-based telescopes. Authors: Babcock, H. W. Bibcode: 1978otf..conf...37B Altcode: Performance criteria for ground-based telescopes are enumerated. They include: (1) the power to differentiate between the image of a faint star and the image of a quasar, (2) resolution of fine structural details within galaxies, and (3) in wide-field photography, the capability of producing aberration-free star images of uniformly good quality over the whole of the large plate. Since seeing is such an important factor, one cannot overemphasize the importance of site selection. Title: First Tests of the Irenee du Pont Telescope Authors: Babcock, Horace W. Bibcode: 1977S&T....54...90B Altcode: No abstract at ADS Title: Guest Investigators at the Hale Observatories Authors: Babcock, Horace W. Bibcode: 1975PASP...87..639B Altcode: No abstract at ADS Title: Guest Investigators at Hale Observatories Authors: Babcock, H. W. Bibcode: 1974PASP...86..340B Altcode: H. W. BABCOCK Hale Observatories Title: Guest Investigators at the Hale Observatories Authors: Babcock, H. W. Bibcode: 1973PASP...85..476B Altcode: H. W. BABCOCK Hale Observatories Title: Guest Investigators at the Hale Observatories Authors: Babcock, H. W. Bibcode: 1972PASP...84..596B Altcode: H. W. BABCOCK Hale Observatories Title: General Magnetic Field of the Sun Authors: Sugiura, M.; Heppner, J. P.; Boldt, E.; Babcock, H. W.; Howard, R. F. Bibcode: 1972AIPH....5..304S Altcode: No abstract at ADS Title: Guest Investigators at the Hale Observatories Authors: Babcock, H. W. Bibcode: 1971PASP...83..375B Altcode: No abstract at ADS Title: Notice: Guest Investigators at the Hale Observatories Authors: Babcock, H. W. Bibcode: 1971BAAS....3..413B Altcode: No abstract at ADS Title: The Las Campanas Observatory Authors: Babcock, H. W. Bibcode: 1971cltd.conf...37B Altcode: No abstract at ADS Title: Guest Investigators at the Hale Observatories Authors: Babcock, H. W. Bibcode: 1970PASP...82..927B Altcode: No abstract at ADS Title: NOTICE Guest Investigators at the Hale Observatories Authors: Babcock, H. W. Bibcode: 1970BAAS....2..280B Altcode: No abstract at ADS Title: Guest Investigators at the Mount Wilson and Palomar Observatories Authors: Babcock, H. W. Bibcode: 1969PASP...81..447B Altcode: No abstract at ADS Title: Guest Investigators at the Mount Wilson and Palomar Observatories Authors: Babcock, H. W. Bibcode: 1968PASP...80..235B Altcode: No abstract at ADS Title: Guest Investigators at the Mount Wilson and Palomar Observatories Authors: Babcock, H. W. Bibcode: 1968AJS....73..159B Altcode: Yellow and blue photoelectric light curves have been obtained for the eclipsing system BR Cygni. A new value of the period has been determined. Orbital elements are derived and a computed light curve is found to compare very well with the yellow observations. A peculiar difference is noted between the yellow and blue light curves at primary minimum. Title: Optical Astronomy in Perspective Authors: Babcock, Horace W. Bibcode: 1967ASPL...10...89B Altcode: 1967ASPL..462.....B No abstract at ADS Title: Optical Astronomy in Perspective Authors: Babcock, Horace W. Bibcode: 1967Sci...156.1317B Altcode: No abstract at ADS Title: Guest Investigators at the Mount Wilson and Palomar Observatories Authors: Babcock, Horace W. Bibcode: 1967PASP...79..262B Altcode: No abstract at ADS Title: Concentration of Elements Over the Surface of a Magnetic Star Authors: Babcock, Horace W. Bibcode: 1967mrs..conf...97B Altcode: No abstract at ADS Title: The Zeeman effect in astrophysics Authors: Babcock, Horace W. Bibcode: 1967Phy....33..102B Altcode: George E. Hale discovered the Zeeman effect in sunspot spectra in 1908, and derived the laws of sunspot polarity. Recent observations of the much weaker (1 to 50 gauss) magnetic fields of the solar photosphere, made with the solar magnetograph, are described. The bearing of these results on circulation in the sun and their consequences for the topology of the sun's magnetic field are mentioned, with reference to the solar cycle and to reversal of the sun's polar field. The problem of measuring the magnetic field of stars is outlined, with reference to instrumental requirements. Spectrographs and crystals are described, together with techniques of measurement of magnetic fields in sharp-line stellar spectra. Results of a systematic program of observations with the 100-inch and 200-inch telescopes are reviewed. All stellar magnetic fields are variable; some are periodic. The strongest yet measured is 34 000 gauss. The magnetic variations are usually related to variations in light, color, line width, and line intensity. Chemical abundance anomalies are common in magnetic stars, and this has led to much work on nuclear reactions in stellar atmospheres, but the phenomena have not been satisfactorily explained. The possible importance of element concentration through paramagnetic migration in strong magnetic field gradients, enhanced by optical pumping, is pointed out. Title: The Solar Magnetic Cycle Authors: Babcock, H. W. Bibcode: 1965ASSL....3....7B Altcode: 1965pss..conf....7B No abstract at ADS Title: Stellar Magnetic Fields Authors: Babcock, H. W. Bibcode: 1964PrCmg...3..393B Altcode: No abstract at ADS Title: Measurement of Stellar Magnetic Fields Authors: Babcock, H. W. Bibcode: 1964aste.book..107B Altcode: 1964S&SS....2..107B No abstract at ADS Title: Instrumental Recording of Astronomical Seeing Authors: Babcock, Horace W. Bibcode: 1963PASP...75....1B Altcode: No abstract at ADS Title: Concentration Elements Over the Surface of a Magnetic Star. Authors: Babcock, H. W. Bibcode: 1963ApJ...137..690B Altcode: No abstract at ADS Title: Magnetic and Light Variations of 53 Camelopardalis Authors: Babcock, Horace W. Bibcode: 1963PASP...75...74B Altcode: No abstract at ADS Title: The Sun's Magnetic Field Authors: Babcock, H. W. Bibcode: 1963ARA&A...1...41B Altcode: No abstract at ADS Title: Photoelectric Recording of Astronomical Seeing. Authors: Babcock, H. W. Bibcode: 1963AJ.....68Q.272B Altcode: An instrument has been built and tested for objectively and continuously monitoring the quality of astronomical seeing. A reticle in the form of a fine grid or lattice is placed at the focus of a small telescope, which is pointed at Polaris. Image tremor (imperfect seeing) causes fluctuations of the light passing the reticle and entering a photomultiplier, thus producing a Fourier frequency spectrum. (The component due to scintillation can be distinguished by occasional defocusing; it is generally of secondary importance.) The signal is analyzed with the aid of an ac amplifier, bandpass filter, rectifier, and recorder. Tests at Mount Wilson have shown that the instrument discriminates well among various grades of seeing, and that it can be calibrated by comparison with large telescopes. Title: The Solar Magnetic Cycle Authors: Babcock, H. W. Bibcode: 1962IAUTB..11..419B Altcode: No abstract at ADS Title: The Topology of the Sun's Magnetic Field and the 22-YEAR Cycle. Authors: Babcock, H. W. Bibcode: 1961ApJ...133..572B Altcode: Shallow submerged lines of force of an initial axisymmetric dipolar field of 8 X 1021 maxwells are drawn out in longitude by the differential rotation (after the suggestion of Cowling) to produce a spiral wrapping of five turns in the north and south hemispheres after 3 years. The amplification factor approaches 45, with a marked dependence on latitude. Twisting of the irregular flux strands by the faster shallow layers in low latitudes forms "ropes" with local concentrations that are brought to the surface by magnetic buoyancy to produce bipolar magnetic regions (BMR's) with associated sunspots and related activity. The field intensity required for producing BMR's is reached at progressively lower latitudes according to the derived formula sin = + 1.5/(n + 3), where n is the number of years since the beginning of the sunspot cycle. This accounts satisfactorily for 's law and the Maunder "butterfly diagram." Sufficient flux rope for more than 102 BMR's is produced. "Preceding" parts of BMR's expand toward the equator as they age, to be neutralized by merging; "following" parts expand or migrate poleward so that their lines of force neutralize and then replace the initial dipolar field. This process, which involves severing and reconnection of lines of force in the corona, as well as expulsion of flux loops, need be only 1 per cent efficient. The result, after sunspot maximum, is a main dipolar field of reversed polarity. The process repeats itself, so that the initial conditions are reproduced after a complete 22-year magnetic cycle. This model accounts for Hale's laws of sunspot polarity and provides a qualitative explanation of the proponderance of "preceding" spots, of the forward tilt of the axes of older spots, of the recurrence of activity in preferred longitudes, and of Hale's chromospheric "whirls." Title: The 34-KILOGAUSS Magnetic Field of HD 215441. Authors: Babcock, Horace W. Bibcode: 1960ApJ...132..521B Altcode: The AOp star HD 215441 has a magnetic field sufficiently strong and uniform to show distinct resolution of many spectrum lines into the ir and components of their Zeeman patterns. The mean field intensity derived from four plates is +34400+ 266 gauss. The field fluctuates irregularly, but 20 plates all show the same polarity. Random variations in radial velocity in the range +3.0 to -8.9 km/sec have been observed. The degree of spectral peculiarity is not extreme, although lines of Si ii, Ti ii, and Cr ii are strong, and the anomalous presence of lines of Fe iii has been noted. Sharp lines of Ca ii, showing a relatively weak Zeeman effect, are judged to arise in a circumstellar cloud having an effective height of 1.2 stellar radii above the surface and showing a mean outward velocity of S km/sec. The magneticenergy density at the surface is 4.6 X 10 ergs/cm3, and the magnetic pressure is sufficient to dominate over the gas pressure in the outer layers of the star. If a 34-kilogauss field prevails throughout the interior, the total internal magnetic energy is about 1041 ergs. Title: Magnetic Fields Associated with the Solar Flare of July 16, 1959. Authors: Howard, Robert; Babcock, Horace W. Bibcode: 1960ApJ...132..218H Altcode: Fourteen "fine-scan" magnetograms at intervals of 15 minutes were obtained during the progress of a large solar flare on July 16, 1959. The pattern of magnetic fields associated with the flare showed no changes other than minor effects attributable to seeing and imperfections in scanning. Title: Test for Polarization in the Integrated Light of Sunspots Authors: Babcock, Horace W. Bibcode: 1960PASP...72..204B Altcode: No abstract at ADS Title: Need for Photoelectric Observations of Magnetic Stars Authors: Babcock, Horace W. Bibcode: 1960PASP...72...53B Altcode: No abstract at ADS Title: Stellar Magnetic Fields Authors: Babcock, H. W. Bibcode: 1960stat.book..282B Altcode: 1960stat.conf..282B; 1960S&SS....6..282B No abstract at ADS Title: Magnetic Field Associated with a Great Solar Flare Authors: Howard, Robert; Cragg, Thomas; Babcock, Horace W. Bibcode: 1959Natur.184..351H Altcode: AN unusually large solar flare, of intensity 3+, was observed at Mount Wilson on July 16, 1959. The flare was in an active region centered on the spot group at approximately 18° N., 29° W. It showed a predominantly S-shaped or double spiral configuration, with marked variations of relative intensity in its various parts. Visual observations of the spectrum showed that the flare commenced abruptly between 21.19 and 21.24 U.T.; maximum was between 22.01 and 22.13 U.T. Lines of Ca II, Na, He and H were observed to be in emission for more than 1 hr.; the width of the Hα emission was greater than 6 A. Emission persisted in the lines of Ca II and of H until after observations were terminated at 01.00 U.T. on July 17. Title: Magnetic Fields of the A-Type Stars. Authors: Babcock, Horace W. Bibcode: 1958ApJ...128..228B Altcode: A discussion of rotational line broadening in the spectra of A-type stars tends to confirm the view that strong coherent magnetic fields are a property of all rapid rotators having convective zones but that fields are observable only in the small proportion of such stars that happen to be observed nearly pole-on. The A stars with observable fields are classed as a-variables (showing periodic magnetic variations); p-variables (irregular magnetic variations with reversal of polarity); -variables (irregular magnetic fluctuations without reversal of polarity); and variables (erratic spectrum variables with irregular magnetic variations). All groups have "peculiar" spectra (abundance anomalies), undoubtedly arising from magnetic activity. The magnetic fluctuations must occur through intrinsic magnetohydrodynamic motions of the stellar material that carries the magnetic lines of force. Irregular atmospheric mixing in the p- and roups results in peculiar spectra but relatively invariant line intensities; a higher degree of organization in the magnetically periodic a-variables results in peculiar spectra with synchronous variations in line intensity A basic physical process must underlie the extraordinary properties of the typical a-variables: they show large-amplitude, nearly symmetric magnetic reversals in periods ranging from 4 to 9 days; they display selective variations in line intensity, as well as the crossover effect and variations in luminosity The proposal is made that this process is a vastly amplified and accelerated magnetohydrodynamic oscillation analogous to the 22-year solar magnetic cycle An alternative model, the oblique rotator, is also discussed Title: Stellar Magnetic Fields Authors: Babcock, H. W. Bibcode: 1958IAUS....6..161B Altcode: No abstract at ADS Title: Photospheric Magnetic Fields Authors: Babcock, H. W.; Babcock, H. D. Bibcode: 1958IAUS....6..239B Altcode: No abstract at ADS Title: A Catalog of Magnetic Stars. Authors: Babcock, Horace W. Bibcode: 1958ApJS....3..141B Altcode: 1957ApJS....3..141B This is a catalog of magnetic stars with a compilation of numerous observations. The analysis and discussion of the results will be taken up in a later paper. The observations have been made over a period of 11 years with the 100-inch and 200-inch telescopes, using an analyzer for the Zeeman effect. Table 1 lists repeated observations of 89 sharp-line stars. Ma etic polarity, field strength, and velocity are tabulated. Notes on spectral peculiarities and line widts are given. Table 2 lists 66 stars that probably, but not definitely, show the Zeeman effect. Table 3 consists of 61 sharp-line stars not showing evidence of a coherent magnetic field. Table 4 is a collection of 122 stars with lines too broad to permit measurement. Of the magnetic stars in Table 1, one is a cluster-type variable, 1 is a subdwarf, 2 are of type S, 3 are M giants, 7 are "metallic4ine" objects, and 70 are A-type stars with sharp or ultra-sharp lines. Stellar magnetic fields are therefore probably ubiquitous. All stellar magnetic fields appear to be variable. Of the A-type stars sufficiently observed, S are regnlar magnetic variables having periods near 1 week, very large and nearly uniform magnetic amplitude, and nearly symmetrical reversal of polarity; about 22 are irregnlar variables showing reversal of polarity; and about 15 are irregnlar variables showing always the same polarity. The irregnlar variations prove that large-scale intrinsic hydromagnetic fluctuations occur in the photospheric layers. Title: Identification of Solar "m" Regions with Unipolar Magnetic Regions. Authors: Babcock, H. W. Bibcode: 1957ApJ...126..224B Altcode: No abstract at ADS Title: The Magnetic Variable HD 71866. Authors: Babcock, Horace W. Bibcode: 1956ApJ...124..489B Altcode: Sixty-one spectrograms made with the differential analyzer for the Zeeman effect have been measured in a study of the magnetic variations of this peculiar A-type star. The strong magnetic field (H = 2 kilogauss; Hp = 6 kilogauss) shows nearly symmetrical reversals of polarity in a period of about 6.8 days that is probably slightly irregular; irregularities in amplitude also occur. The lines of Eu ii under- go moderate variations in intensity in phase with the magnetic variations, but the spectrum variability is of much lower degree than that of HD 125248 Velocity measurements yield only random fluctuations within a range of several kilometers per second, without definite evidence for harmonic variations. The star may be classed along with a2 CVn, HD 153882, and HD 125248 as one of a small group of regularly reversing magnetic variables of large and nearly equal amplitude, all of which have periods of about 1 week. The crossover effect on the line profiles in polarized light is unusually prominent for Fe I but is much less so for lines of ionized elements. On the reasonable assumption that the visibility of the effect is near maximum owing to a matching of the Zeeman displacements by Doppler displacements for two hypothetical areas of opposite magnetic polarity, the matching velocity is derived from several lines of Fe I; it is about S km/sec. On the "rotator niodel" this leads to a V (axial rotation) of 3.5 km/sec, whereas an AO star with a period of axial rotation of 6.8 days should have V = 16 km/sec. Furthermore, the line widths in HD 71866, by direct measurement, are appreciably narrower than would be indicated by the rotator model Title: An Improved Automatic Guider Authors: Babcock, H. W.; Rule, B. H.; Fassero, J. S. Bibcode: 1956PASP...68..256B Altcode: No abstract at ADS Title: Magnetic Field of RR Lyrae Authors: Babcock, Horace W. Bibcode: 1956PASP...68...70B Altcode: No abstract at ADS Title: Association of a "Unipolar" Magnetic Region on the Sun with Changes of Primary Cosmic-Ray Intensity Authors: Simpson, J. A.; Babcock, H. W.; Babcock, H. D. Bibcode: 1955PhRv...98.1402S Altcode: A new instrument for observing weak magnetic fields on the photosphere of the sun has recently revealed the presence of an unusual area on the solar surface which may be called a "unipolar" magnetic (UM) region because the field is of one sign and no magnetic flux has been found returning to the sun. A region of this type was observed at central solar meridian on seven consecutive solar rotations in 1953. In the present paper it is shown that there is a striking association of this UM region with (1) times of maximum primary cosmic ray intensity as measured by neutron detectors and an ionization chamber, and with (2) the recurring geomagnetic storms-the geomagnetic disturbances being most pronounced ~3-4 days after both the central meridian passage of the UM region and the time of maximum cosmic-ray intensity. Title: The Sun's Magnetic Field, 1952-1954. Authors: Babcock, Horace W.; Babcock, Harold D. Bibcode: 1955ApJ...121..349B Altcode: More than 450 magnetograms, showing the distribution, intensity, and polarity of weak magnetic fields (> 0.3 gauss) on the sun have been obtained with the solar magnetograph over a two-year period. This interval includes the recent minimum of solar magnetic activity. The records show a pattern with a fluctuating fine structure and certain large-scale regularities. General magnetic fietd.-Consistent evidence is found for a general field, predominantly dipolar, with polarity opposite to that of the earth. The mean intensity is of the order of 1 gauss. The general field is usually limited to heliographic latitudes greater than about t 550; it has a varying fine structure and shows remarkable random fluctuations in effective intensity and extent. There seems to be no prevailing obliquity between the magnetic and rotational axes. The total flux is estimated to be nearly 10 maxwells. Bipolar magnetic (BM) regions.-In the lower latitndes the stronger magnetic effects appear as contiguous areas of opposite magnetic polarity, as if loops of a submerged toroidal field were occasionally brought to the surface by rising material. The BM regions obey Hale's laws of sunspot polarity, but spots are comparatively rare, occurring, when at all, within the BM regions while they are young. Ca ii plages are observed where the field intensity is greater than about 2 gauss. Hydrogen filaments occur around the borders of BM regions or, alternatively, seem to divide the region into parts of opposite polarity. As the regions age, they generally expand, showing a decrease in field intensity, and disintegrate until lost in the background of irregular weak fields. There is much diversity in total magnetic flux, duration, area, and course of development. Unipolar magnetic (UM) regions.-Occasional extended magnetic areas of only one outstanding polarity were recognized. The most prominent UM region of 1953 had an intensity 3 gauss and a duration of many months; it may well have been related to a prominent sequence of 27-day-recurrent terrestrial magnetic storms. UM regions may be remnants of disintegrating BM regions. We suggest that UM regions may be identified as the heretofore hypothetical "M" regions of Bartels. Repeated tracings of the same area of the sun at intervals of a few minutes show changes of the order of 1 gauss in the fine structure of the magnetic pattern within a half-hour. The observations provide objective evidence for the heretofore inferential hypothesis that magnetic fields are fundamental to sunspots, plages, prominences, chromospheric fine structure, bright coronal emissions, and, probably, regions of strong radio emission. Several solar phenomena can be synthesized on the proposition that neutral but ionized corpuscular streams are continually being ejected from all turbulent regions of the surface characterized by coherent magnetic fields of average intensity gauss or more. A hydromagnetic model, based on chromospheric spicules, is proposed for such ejection. Title: Book Reviews: Astronomical Photoelectric Photometry Authors: Babcock, Horace W. Bibcode: 1954SciMo..79...61W Altcode: No abstract at ADS Title: The Magnetic Variable HD 188041. Authors: Babcock, Horace W. Bibcode: 1954ApJ...120...66B Altcode: Fifty-seven observations of the magnetic field of HD 188041 have been made at intervals during the last seven years. The field is always of positive polarity but varies between the extreme limits 600 and 4800 gauss, with some irregnlarities in amplitude, in a period of 226 days The star is also a spectrum variable in which lines of Eu rr, Gd ii, and Sr ii are stronger when the field is strong; the phase of the intensity-curve for Gd ii is earlier than the magnetic curve by about 0.1 of the period. When the field is increasing most rapidly, Gd ii shows a stronger magnetic-field intensity than do other elements, and Fe II shows a stronger field than Fe I. The velocity shows small random fluctuations. Title: The Polarity of the Sun's Magnetic Field and the Richardson-Schwarzschild Oscillation. Authors: Babcock, Horace W. Bibcode: 1954ApJ...119..687B Altcode: No abstract at ADS Title: Stellar Wave Lengths of EU II as Affected by Hyperfine Structure. Authors: Babcock, Horace W. Bibcode: 1954ApJ...119..463B Altcode: No abstract at ADS Title: The flash spectrum without eclipse Authors: Babcock, H. W. Bibcode: 1953Obs....73..241B Altcode: No abstract at ADS Title: The Solar Magnetograph. Authors: Babcock, Horace W. Bibcode: 1953ApJ...118..387B Altcode: A new instrument for measuring and recording weak magnetic fields on the surface of the sun has been developed for use with the 150-foot solar telescope and 75-foot spectrograph of the Hale Solar Laboratory. Principal features include: a superior grating of high resolving power for use in the fifth-order spectrum; an electro-o tic analyzer for polarization; a double-slit detector for the longitudinal Zeeman effect; and a self-sync ronous system by which the disk of the sun is scanned in a raster of parallel traces, the results as to magnetic intensity and polarity being presented conformally on the screen of a cathode-ray tube and recorded by a camera. The noise level (about 0.1 gauss) is such that fields of the order of 1 gauss can be recorded readily. The method of calibration is described, and the possibility is pointed out of using the instrument, with a slight optical modification, for studying small Doppler shifts in the sun's atmosphere. Title: The Possibility of Compensating Astronomical Seeing Authors: Babcock, H. W. Bibcode: 1953PASP...65..229B Altcode: No abstract at ADS Title: Magnetic Observations of HD 188041 and HD 133029 Authors: Babcock, Horace W. Bibcode: 1953PASP...65..194B Altcode: No abstract at ADS Title: Mapping the Magnetic Fields of the Sun Authors: Babcock, Horace W.; Babcock, Harold D. Bibcode: 1953sun..book..704B Altcode: No abstract at ADS Title: The Magnetically Variable Star HD 153882. Authors: Gjellestad, Guro; Babcock, Horace W. Bibcode: 1953ApJ...117...12G Altcode: The reversing magnetic field of the peculiar A-type star HD 153882 has been investigated on twenty spectrograms made with the double analyzer for circularly polarized light. The effective magnetic field intensity at the pole, H , as determined from measures of the Zeeman effect on about thirty jines on each plate, varies periodically between the limits t4SOO gauss and - 4000 gauss. The derived period is 6.005 days. Measures of Hp and of radial velocity have been tabulated for elements at various phases. The mean velocity-curve is anharmonic, with a range of 5.3 Irm/sec. Systematic velocity differences between elements are small; this is probably related to the fact that the spectrum shows little or no variability in relative line intensities. The spectrum is peculiar in that Cr I, Cr Ir, and Mn I are strong, and the K line is sharp, but the star is not a typical spectrum variable. A cross-over effect in the polarized line profiles, rather similar to that previously found in lID 125248 and in a2 CVn, was observed at phases when the effective magnetic field is near zero. Title: General magnetic fields in the Sun and stars (Report on progress of astronomy) Authors: Babcock, H. W.; Cowling, T. G. Bibcode: 1953MNRAS.113..357B Altcode: Since the early work of G. E. Hale (x, 2) a number of attempts have been made to detect and measure the general magnetic field of the Sun. Also magnetic fields on a large scale have been observed in a variety of stars. The first part of this report (by H.W.B.) will give a brief survey of the observational work on such fields. Theories of the fields will be briefly discussed in the second part (by T.G.C.). Title: Mapping the Magnetic Fields of the Sun Authors: Babcock, Horace W.; Babcock, H. D. Bibcode: 1952PASP...64..282B Altcode: No abstract at ADS Title: The Magnetically Variable Star HD 153882 Authors: Gjellestad, Guro; Babcock, Horace W. Bibcode: 1952PASP...64..226G Altcode: No abstract at ADS Title: The Variable Magnetic Field of α^{2} Canum Venaticorum. Authors: Babcock, Horace W.; Burd, Sylvia Bibcode: 1952ApJ...116....8B Altcode: This well-known peculiar star is found to have a strong magnetic field, the polarity of which is reversed in step with the periodic changes in line intensity. The Zeeman effect has been investigated on twenty-one spectrograms made with the double polarizing analyzer. Polar magnetic-field strength and radial velocity for various elements have been tabulated as a function of phase in the period of 5.5 days. The extremes of Hp are approximately -4000 gauss when the Eu ii lines are at maximum intensity and +5000 gauss a half-period later, when Cr ii is at maximum. Title: Magneto-hydrodynamic oscillations of a star Authors: Gjellestad, G.; Babcock, H. W. Bibcode: 1952AnAp...15..276G Altcode: No abstract at ADS Title: Stellar magnetism. Authors: Babcock, H. W. Bibcode: 1951AJ.....56..116B Altcode: No abstract at ADS Title: The Magnetically Variable Star HD 125248. Authors: Babcock, Horace W. Bibcode: 1951ApJ...114....1B Altcode: The reversing magnetic field of the peculiar A-type star HD 125248 = BD - has been investigated on twenty-seven high-dispersion spectrograms made with the double analyzer for circularly polarized light. The magnetic-field intensity at the pole, Hp, as determined from the Zeeman effect on numerous Fraunhofer lines, has been tabulated for several elements at different phases in the 9.295-day period found by Deutsch for the variations in line intensity. The lines of Fe I, Fe ii, and Ti ii, which vary only slightly in intensity, indicate a field represented by Hp = 2000 + 6600 cos 0-1600 cos 20 gauss. The positive extreme (+7000 gauss) is reached near zero phase, when the lines of the rare earths are at maximum intensity and lines of Cr I and Cr ii are at minimum. The negative extreme (-6200 gauss) is reached at mid-period when Eu ii is weak and Cr is at maximum intensity. Hp determined from the Cr lines is "more negative" than that indicated by Fe-Ti, while, especially at the "cross-over" phases (0.35 and 0.7, when Hp = 0), Eu ii gives a stronger positive field. If results from all elements are averaged, the extremes are close to +7600 and - 7600 gauss. Velocities in the line of sight are also tabulated for elements at various phases. Again, systematic differences are found between the Fe-Ti group, the rare-earth group, and Cr. Rather sudden decelerations occur just as 11p reaches maximum. A "cross-over effect" on the profiles of Fraunhofer lines was discovered on plates made near phases 0.35 and 0.7. This is interpreted as a combination of differential velocity and temporary opposite magnetic polarity on two zones of the star; apparently, the magnetic field reverses in a rapid, progressive manner over the surface. The rare earths and Cr seem to be concentrated in separate atmospheric zones, which vary in effective size or location; Fe and Ti are supposed to be rather uniformly distributed and to represent best the general magnetic field. Two fundamentally different physical models are considered: the magnetic oscillator and the oblique rotator. The latter does not satisfactorily represent the observations. Consequently, it is concluded that HD 125248 is observed pole-on and that it is oscillating, perhaps in a manner suggested by Schwarzschild, for only by large-scale motions of the material of the star can rapid changes of the magnetic field be explained. In his solution (odd mode), specialized pulsations of the star are coupled with an oscillating dipole component of the field. The constant component (+2000 gauss) indicated by Fe-Ti can perhaps be interpreted most plausibly according to the Elsasser-Bullard theory, although the observations yield no data as to rate of axial rotation (or as to differential rotation). For lack of these data the electromotive forces in the atmosphere cannot be specified completely; however, the oscillating component of the electric field induced by the changing magnetic field is specified in Schwarzschild's solution (for a nonconducting atmosphere). This has an an plltude at the equator of 36 volts/cm. To account for the varying equivalent widths of lines, it is assumed that the effective atmospheric Eu and Cr have become concentrated in zones, Eu near the poles, Cr in an equatorial belt, and that the extent of these zones varies as the star oscillates. As a tentative approach to this separation of elements, a mass-spectrograph effect is considered, depending upon the transient differential drift velocities of ions, as a function of charge/mass, in crossed electric and magnetic fields. Title: The ruling of diffraction gratings at the Mount Wilson Observatory. Authors: Babcock, Harold D.; Babcock, Horace W. Bibcode: 1951AJ.....56Q.120B Altcode: The newer ruling engine of the Mount Wilson Observatory is now producing sizeable diffraction gratings of high quality in all respects. Several recent gratings are 7~41 inches wide with grooves 543 inches long, and one is 8 by 5~' inches. Curved-edge ruling diamonds, developed here, have been used in blazing these gratings to specifications for astronomical use. High luminous efficiency is combined with practically complete absence of scattered light, either general or local in the spectrum. Resolving power of 500,000 is achieved. Rowland ghost intensity is held to about 0.00004 in the first order of 15,000 line per inch rulings and is negligible. Most ruling to date has been at 300, 400, 600, or 900 grooves per millimeter, but other spacings are available. The rather considerable modifications of the Rowland-type engine are described, with particular reference to the monorail diamond carriage, the coupling of the nut to the grating carriage, the end-thrust bearing of the screw, the use of Xitralloy steel ways, and the spacing mechanism. That the principles of this entirely mechanical, single-screw machine are thoroughly sound is attested by the quality of its products. Blazed plane gratings have almost entirely supplanted prisms in fast stellar spectrographs of both short and long focus. Our methods of testing gratings are outline~ and a formula is proposed for the evaluation of gratings. Mount Wilson and Palomar Observatories, Pasadena, Ca 1sf. Title: The Strong Magnetic Field of HD 133029 Authors: Babcock, Horace W.; Burd, Sylvia Bibcode: 1951PASP...63...81B Altcode: No abstract at ADS Title: Magnetic Field of a Late-Type Star, HD 4174 Authors: Babcock, Horace W. Bibcode: 1950PASP...62..277B Altcode: No abstract at ADS Title: Stellar Magnetic Fields Authors: Babcock, H. W. Bibcode: 1950Natur.166..249B Altcode: No abstract at ADS Title: A Contour Photometer Authors: Babcock, H. W. Bibcode: 1950PASP...62...18B Altcode: No abstract at ADS Title: Three Magnetic Variable Stars Showing Reversal of Polarity Authors: Babcock, H. W. Bibcode: 1949PASP...61..226B Altcode: No abstract at ADS Title: Stellar magnetic fields and rotation Authors: Babcock, H. W. Bibcode: 1949Obs....69..191B Altcode: No abstract at ADS Title: Magnetic Intensification of Stellar Absorption Lines. Authors: Babcock, Horace W. Bibcode: 1949ApJ...110..126B Altcode: The total intensity of a saturated absorption line may be increased several fold in a magnetic field of a few kilogauss because the Zeeman pattern may be considerably wider than the thermal Doppler profile. The effect should be particularly marked for lines having wide, anomalous Zeeman patterns of many components; it is enhanced for elements of high atomic weight at reduced temperatures and in the ab- sence of turbulence. An upper limit to the intensification factor is half the number of components in the Zeeman pattern of the line. A method is developed for computing the magnetic intensification, W~/W0, for a saturated line of given pattern in integrated light of a star viewed from the direction of the pole (i = 00) or viewed from the plane of the star's equator (~ = 90°). For the line Fe i X 4260, having a triplet pattern (Z = 1.60), W~/Wo = 1.25 for a field of 8 kilogauss and a temperature of 10,000°. The intensification factor appears to be essentially independent of i; it may approach 7 for an exceptional line like Eu ii X 4205, which has 21 widespread components. If equivalent widths can be measured, it should be possible in principle to estimate stellar magnetic field strengths by detailed comparisons of lines se]ectively intensified by Zeeman splitting, even if pronounced rotational broadening is present. In a number of the peculiar stars of type A, magnetic fields ranging up to several kilogauss have been measured with the polarizing analyzer; the conclusion is practically inescapable that magnetic intensifica- tion must contribute to the abnormal line intensities in the spectra of some of these stars. For about fifty lines in the spectrum of a2 CVn, for which intensity estimates at three phases of the spectral variation have been published by Struve and Swings, the degree of observed intensity variation is compared with the magnetic intensification factor predicted from the Zeeman patterns; a satisfactory correspondence is found. I. INTRODUCTIO Title: Test for a Magnetic Field in the White Dwarf 40 Eridani B Authors: Babcock, Horace W. Bibcode: 1948PASP...60..368B Altcode: No abstract at ADS Title: The Magnetic Field of γ Equulei. Authors: Babcock, Horace W. Bibcode: 1948ApJ...108..191B Altcode: The present status of the observational work on stellar magnetic fields determined through analysis of the Zeeman effect is briefly summarized. The strongest fields have been found in the peculiar stars of types A and early F, particularly in the spectrum variables. Some of the magnetic fields are variable. In y Equulei, however, there is no conclusive evidence that the field varies; measures of forty-seven lines on each of four or five plates of dispersion 2.9 A/mm give H~ = 1900 ± 250 (p.e.) gauss. The magnetic polarity observed is positive in y Equ, negative in 78 Virginis. Magnetic moment and rotation in `y Equ are probably antiparallel, as in the earth. Lines of medium and strong intensity yield a somewhat smaller H~ than do weak lines. This result is interpreted as the effect of the curve of growth on the Zeeman components of the stronger lines. * The proportionality between magnetic moment and angu'ar momentum is briefly discussed, with consideration of variable fields. INTRODUCTIO Title: Magnetic Intensification of Absorption Lines Authors: Babcock, Horace W. Bibcode: 1948PASP...60..245B Altcode: No abstract at ADS Title: Magnetic Variable Stars as Sources of Cosmic Rays Authors: Babcock, Horace W. Bibcode: 1948PhRv...74..489B Altcode: No abstract at ADS Title: A Photoelectric Guider for Astronomical Telescopes. Authors: Babcock, Horace W. Bibcode: 1948ApJ...107...73B Altcode: A new and simple method of optical scanning with a rotating knife-edge, in combination with the modern electron multiplier phototube, makes practicable for the first time an automatic device for guid- ing astronomical telescopes. A comparatively simple guider, working in both right ascension and declina- tion and employing a single phototube, is performing satisfactorily in guiding the 100-inch reflector for high-dispersion spectrographic work. T1~e instrument compensates for fluctuations in the apparent posi- lion of the star due to "seeing" and for residual errors in the driving mechanism of the telescope Title: No. 739. A photoelectric guider for astronomical telescopes. Authors: Babcock, Horace W. Bibcode: 1948CMWCI.739....1B Altcode: 1948QB4.M93n739.... No abstract at ADS Title: An Automatic Guider for Astronomical Telescopes Authors: Babcock, Horace W. Bibcode: 1947RScI...18..854B Altcode: No abstract at ADS Title: The Reversing Magnetic Field of BD-18°3789 Authors: Babcock, Horace W. Bibcode: 1947PASP...59..260B Altcode: No abstract at ADS Title: Magnetic Fields of Astronomical Bodies Authors: Babcock, Horace W. Bibcode: 1947PhRv...72...83B Altcode: No abstract at ADS Title: Remarks on Stellar Magnetism Authors: Babcock, Horace W. Bibcode: 1947PASP...59..112B Altcode: No abstract at ADS Title: Zeeman Effect in Stellar Spectra. Authors: Babcock, H. W. Bibcode: 1947ApJ...105..105B Altcode: Some stars of early spectral type which exhibit sharp metallic lines may be in rapid rotation, with their axes directed nearly toward the observer. On the possibility that strong magnetic fields are corre- lated with rapid rotation in such objects, the Zeeman effect for a normal triplet line, as observed through a circular analyzer, has been integrated over the visible hemisphere of the star. Reasonable assumptions are made regarding field distribution and limb darkening. It is found that the integrated Zeeman effect for a normal triplet should give a displacement of about 3 X 106 A/gauss at A 4600. Observations of the star 78 Vir (type A2p), made with a differential circular analyzer in front of the slit of the coudé spectrograph of the 100-inch telescope, show displacements of the metallic absorption lines that are interpreted as a Zeeman effect resulting from a general magnetic field having a strength of 1500 gauss at the pole. The control star ~ Peg (type KO) shows no effect Title: No. 727. Zeeman Effect in stellar spectra. Authors: Babcock, H. W. Bibcode: 1947CMWCI.727....1B Altcode: 1947QB4.M93n727.... No abstract at ADS Title: The Spectrum of Zcamelopardalis and of Other U Geminorum-Type Variables Authors: Elvey, C. T.; Babcock, H. W. Bibcode: 1946PAAS...10...51E Altcode: No abstract at ADS Title: The Spectra of U Geminorum Type Variable Stars. Authors: Elvey, C. T.; Babcock, H. W. Bibcode: 1943ApJ....97..412E Altcode: Spectrograms of several U Geminorum variable stars and of a few related objects have been obtained with the Cassegrain spectrographs on the 82-inch telescope. The linear dispersions varied from 75 A/mm to 340 A/mm at Hy. Descriptions of the spectra of the following objects are given for one or more phases in their light-curves: UTJ Aqi, SS Aur, SS Cyg, U Gem, X Leo, AY Lyr, RU Peg, STJ TJMa, TW Vir, RX And, Z Cam, All Her, CN On, TZ Per, EY Cyg, CY Lyr, CO On, UX On, CL Sco, T Pyx, and V Sge. A brief summary is given of the characteristics of the spectra of the U Geminorum type of variable stars at minimum and maximum light Title: Development of the Coronaviser. Authors: Babcock, H. W. Bibcode: 1942ApJ....96..242B Altcode: The principles of the coronaviser are discussed, and an equation is developed by means of which the performance of the instrument can be predicted in terms of several disposable parameters. The equation indicates that some degree of useful performance should be attainable under favorable conditions. The original coronaviser of Skellett was tested at the McDonald Observatory, but without positive results. Following this, a new scanning mechanism, in combination with an optical system of the Lyot type, was constructed. Tests of this instrument have not been completed, but a report of progress is given now, as the work must be laid aside for some time Title: Note: Remarks on the Spectra of Comets 1941c Paraskevopoulos-De Kock) and 1941d (van Gent). Authors: Elvey, C. T.; Swings, P.; Babcock, H. W. Bibcode: 1942ApJ....95..218E Altcode: No abstract at ADS Title: A Spectrophotometric Study of the Light of the Night Sky Authors: Babcock, H. W.; Johnson, J. J. Bibcode: 1941ApJ....94..271B Altcode: A spectrophotometric comparison of the night sky and M ~ i shows that the night sky is relatively much stronger than the nebula in ultraviolet light and suggests that for nebular photography improved contrast may be obtained by the use of a filter to remove ultraviolet light. An extensive series of intensity measurements of night-sky radiations shows that no marked varia- tions may be expected within a single night, in the absence of polar auroras, but that on occasional nights the sky is extraordinarily bright, thus greatly reducing the efficiency of direct photography. If periods of unusual activity are excepted, X 5577 and the red pair of lines at X 6300 and X 6364 seem to vary lila com- plementary fashion throughout a given night, but over longer intervals all radiations tend to vary similarly and together Title: The Spectrum of Comet Cunningham, 1940C. Authors: Swings, P.; Elvey, C. T.; Babcock, H. W. Bibcode: 1941ApJ....94..320S Altcode: Slit spectrograms of Comet Cunningham secured at the McDonald Observatory reveal well-resolved ultraviolet bands due to OH and NH; oniy the lines of low rotational quantum number are observed, as in the case of CH. The abundances of OH and NH molecules seem to be of the same order as that of CN. Each branch of the violet bands of CN has two maxima, one corresponding to a rotational distribution for T - 400° K and one corresponding to T 500 K. The tail bands of CN are absent. The authors dis- cuss the variation with heliocentric distance of the relative intensities of the vibrational transitions. The rotational intensity distribution and the extension of the different bands in the head have been investi- gated. The cometary bands of CH belonging to the two electronic transitions, A2L~ -~ x211 (near X 4300) and B2»=~ -~ x211 (near X 3900), are described. The bands observed between X 4000 and X 4130 are dis- cussed but remain unidentified Title: La rotation de la Nébuleuse d'Andromède (Lick. Bull. 498, oct. 1939) Authors: Babcock, H. W. Bibcode: 1941C&T....57...91B Altcode: No abstract at ADS Title: Interstellar Absorption Near the North Pole of Rotation. Authors: Keenan, Philip C.; Babcock, Horace W. Bibcode: 1941ApJ....93...64K Altcode: Revised spectral classes for B8-A~ stars north of +800 declination confirm essentially the variation of interstellar absorption with distance found by Stebbins, Huffer, and Whitford for these stars. The total visual absorption, which is inappreciable for distances less than 200 parsecs, increases to 0.3 mag. at 400 parsecs Title: Radiations of the Night Sky Photographed with a Grating Authors: Babcock, Horace W. Bibcode: 1939PASP...51...47B Altcode: No abstract at ADS Title: The rotation of the Andromeda Nebula Authors: Babcock, Horace W. Bibcode: 1939LicOB..19...41B Altcode: 1939LicOB.498...41B No abstract at ADS Title: Spectrographic Observations of the Rotation of the Andromeda Nebula Authors: Babcock, Horace W. Bibcode: 1938PASP...50..174B Altcode: No abstract at ADS Title: On the Rotation of the Andromenda Nebula. Authors: Babcock, Horace W. Bibcode: 1938PhDT.........1B Altcode: No abstract at ADS Title: Recent Observations of Solar Chromospheric and Disk Spectra in the Infra-Red Authors: Babcock, H. W. Bibcode: 1935PASP...47..321B Altcode: No abstract at ADS Title: Some New Features of the Solar Spectrum Authors: Babcock, H. D.; Babcock, H. W. Bibcode: 1934PASP...46..132B Altcode: No abstract at ADS Title: The Paschen Series of Hydrogen Lines in the Spectrum of the Solar Chromosphere Authors: Babcock, H. W. Bibcode: 1932PASP...44..323B Altcode: No abstract at ADS