Author name code: pierce ADS astronomy entries on 2022-09-14 =author:"Pierce, A. Keith" OR =author:"Pierce, A.K." ------------------------------------------------------------------------ Title: Wavelength Shifts in the Solar Photospheric Spectrum Authors: Pierce, A. Keith; Lopresto, James C. Bibcode: 2000SoPh..196...41P Altcode: Wavelength shifts converted to velocities between solar lines observed at disc center and laboratory wavelengths of Fe i, Fe ii, Ti i, Ni i, and Fe i lines in the near infrared are plotted as a function of the logarithm of their solar equivalent width in milliångstroms. The need for wavelengths based on the wavelength standards is stressed. A comparison of photographic Fe i solar wavelength is shown to agree, on the average, with Fourier Transform Spectrometer solar wavelengths within less than 0.5 milliångstroms. Using Balthasar's limb effect tables we convert the disc center velocities to limb velocities and find, though the scatter is large, that there is little evidence for a super-gravitational red shift. Title: Observations of the limb effect in potassium λ7699 Authors: Lopresto, J. C.; Kraus, Pauline M.; Pierce, A. K. Bibcode: 1994SoPh..149..243L Altcode: Center-to-limb observations of the KI λ7699 line made on 30 days over a five-year period using the McMath-Pierce Solar Telescope at Kitt Peak are presented. Both a relative and absolute limb effect have been derived from the data. Our determination of the limb effect in KI λ7699 shows a linear increase to the limb amounting to about 40 m s−1. Title: The Observed Limb Effect in Fraunhofer Lines - Part Two Authors: Pierce, A. K. Bibcode: 1992SoPh..139....1P Altcode: In this paper the absolute limb effect for a number of Fraunhofer lines observed at the McMath Solar Observatory is given. Results, uncorrected for scattered light, are given for the following lines: FeIλ37334.9, λ3735.3, λ5123.7, λ5250.2, λ5434.5, λ6678.0, and λ8886.6. Additional lines observed are five lines of CN λλ3876.3-3880.0, two lines of CaIλ6161.3 and λ6162.2, one line of NaI, λ6160.7, and one CN line (λ7957.0) of the red system. Title: Solar Gravitational Redshift from the Infrared Oxygen Triplet Authors: Lopresto, James C.; Schrader, Charles; Pierce, A. K. Bibcode: 1991ApJ...376..757L Altcode: The difference in wavelength between the IR oxygen triplet 7772-7775 A in the sun and in the laboratory has been observed. Converted to velocities, the disk values, extrapolated to the limb, give a redshift of 655 m/s compared to the value of 636 m/s predicted from the principal of equivalence. Observations of the chromospheric oxygen lines in emission just off the sun's limb give a velocity of 627 m/s or 0.99 of the Einstein prediction. Title: The Observed Limb Effect in Fraunhofer Lines - Part One Authors: Pierce, A. K. Bibcode: 1991SoPh..133..215P Altcode: The absolute limb effect is presented for FeI lines λ 3767 and λ3969; for five TiI lines of multiplet 42 near λ 4535 and one TiII line at λ 4534; two lines of MgI, λ 4571 and λ 5172; two lines of BaII at λ 5854 and λ 6497. The scattered light of the McMath solar telescope is illustrated by several figures but not applied to the limb-effect observations. It is suggested that the supergravity shift at the limb is the result of scattering of the atoms in anisotropic velocity field. Title: The Solar Gravitational Red Shift Authors: Lopresto, J. C.; Pierce, A. K. Bibcode: 1989BAAS...21..752L Altcode: No abstract at ADS Title: A Windscreen around the Heliostat of the Mcmath Solar Telescope Authors: Pierce, A. Keith Bibcode: 1987SoPh..107..397P Altcode: No abstract at ADS Title: Solar Meridional Flow Authors: Pierce, A. Keith; Lopresto, James C. Bibcode: 1987BAAS...19..935P Altcode: No abstract at ADS Title: Solar Gravitational Red Shifts of 07772A and K7699A Authors: Lopresto, James C.; Pierce, A. Keith Bibcode: 1987BAAS...19..942L Altcode: No abstract at ADS Title: The Morphology of Solar Granulations and Dark Networks Authors: Graves, J. Elon; Pierce, A. Keith Bibcode: 1986SoPh..106..249G Altcode: Solar granules are classified into four groups according to their shapes and splitting by sharp rifts crossing them. The appearance and evolution of `white-light dark networks' is described. Title: The center-to-limb wavelength shift of a number of Fraunhofer lines Authors: Lopresto, J. C.; Pierce, A. K. Bibcode: 1985SoPh..102...21L Altcode: The center-to-limb wavelength shifts of the cores of faint, medium and strong Fraunhofer lines are presented: FeI 3767, CaII 3968, CeII 4222, CaI 4227, NaI 5896, BaII 6497, and KI 7699. Title: Center to Limb Behavior of Some Strong and Medium Strong Fraunhoffer Lines Authors: Lopresto, J. C.; Pierce, A. K. Bibcode: 1985BAAS...17R.756L Altcode: No abstract at ADS Title: Investigation of Photospheric Limb-Darkening Variation Between 1980 and 1985 Authors: Petro, L. D.; Foukal, P. V.; Rosen, W. A.; Pierce, A. K.; Kurucz, R. L. Bibcode: 1985BAAS...17..644P Altcode: No abstract at ADS Title: Center to Limb Behavior of Some Strong Fraunhofer Lines Authors: Lopresto, J. C.; Pierce, A. K. Bibcode: 1984BAAS...16.1001L Altcode: No abstract at ADS Title: A study of solar photospheric limb-darkening variations Authors: Petro, L. D.; Foukal, P. V.; Rosen, W. A.; Kurucz, R. L.; Pierce, A. K. Bibcode: 1984ApJ...283..426P Altcode: The authors have obtained regular observations of photospheric limb darkening, using the McMath Solar Telescope, to study possible slow changes in the global temperature structure, in Teff, and in the ultraviolet continuum flux from the quiet Sun. This paper reports on the analysis of data obtained on 15 days between 1980 September and 1982 December in a continuum window at λ4451. There are no variations of global limb darkening exceeding 0.1% at the 99% confidence level. The implications of these measurements for slow changes in solar luminosity, convection zone structure, and ultraviolet flux are discussed. Title: Solar Rotation from a Number of Fraunhofer Lines Authors: Pierce, A. K.; Lopresto, J. C. Bibcode: 1984SoPh...93..155P Altcode: Solar differential rotation for 1982-83 obtained at the double pass spectrograph of the McMath telescope at Kitt Peak, are presented for lines of Fe, Mg, Na, K, Si, and O in the wavelength interval λλ3820-10827. The results are analyzed by representations in Legendre polynominals and a power series. The differential rotation is very close to the result obtained by Howard and Harvey in 1966-68 at Mt. Wilson but with a slightly greater amplititude. We find a mean equatorial rate of rotation of 1.977 km s-1. Day to day variations are observed in the equatorial zone; a stable rate of rotation is observed outside of the sunspot zone. Title: Solar Rotation From a Number of Fraunhofer Lines Authors: Lopresto, J. C.; Pierce, A. K. Bibcode: 1984BAAS...16..532L Altcode: No abstract at ADS Title: Fraunhofer Line Profiles Authors: Pierce, A. Keith Bibcode: 1984SoPh...90..195P Altcode: It is shown that comparing an observed Fraunhofer profile to a fitted gaussian yields more information on shape and asymmetry of the solar line than the simple bisector method. Title: Variation of Solar Limb Darkening Authors: Petro, L. D.; Foukal, P. V.; Rosen, W. A.; Kurucz, R. L.; Pierce, A. K. Bibcode: 1983BAAS...15..951P Altcode: No abstract at ADS Title: Variations in photospheric limb darkening as a diagnostic of changes in solar luminosity Authors: Rosen, W. A.; Foukal, P. V.; Kurucz, R. L.; Pierce, A. K. Bibcode: 1982ApJ...253L..89R Altcode: The paper reports on photospheric limb-darkening measurements obtained with the McMath Solar Telescope in July, September, and October 1980 as part of a continuing program to investigate possible long-term variations in the photospheric emergent flux. A total of 243 usable full-diameter scans were recorded over seven days in the clean continuum window at 4451-25 A. The limb darkening was found to decrease significantly between September 25 and 26. It is suggested that this decrease was caused by a decrease of the temperature gradient in the upper photosphere in the region above approximately tau(5000) = 0.5. The small increase in effective temperature that might accompany this limb-darkening variation is estimated using a standard radiative equilibrium photospheric model. Title: Center to limb observations of sodium lines in the solar spectrum Authors: Pierce, A. K.; Slaughter, C. Bibcode: 1982ApJS...48...73P Altcode: Center to limb (cos theta = 1.0 to 0.1) intensities are given for the profiles of 25 sodium lines distributed at wavelengths from 3302 to 22083 A in the solar spectrum. Central intensities and half-widths are tabulated for five additional sodium lines. Title: Photospheric Limb Darkening as a Ground-based Diagnostic for Variations in the Solar Effective Temperature Authors: Rosen, W. A.; Foukal, P. V.; Kurucz, R.; Pierce, A. K. Bibcode: 1981BAAS...13..551R Altcode: No abstract at ADS Title: Solar limb darkening in the interval 7404 - 24018 Å, II. Authors: Pierce, A. K.; Slaughter, C. D.; Weinberger, D. Bibcode: 1977SoPh...52..179P Altcode: The coefficients of third degree and fifth degree polynomial representations of limb darkening are tabulated for 50 wavelengths in the interval λλ 7404-24 018. Title: Solar limb darkening. I: lambda lambda (3033 - 7297). Authors: Pierce, A. K.; Slaughter, C. D. Bibcode: 1977SoPh...51...25P Altcode: The coefficients of several polynomial representations of the limb darkening at 62 wavelengths in the UV and visible portions of the solar spectrum obtained at the McMath Solar Telescope are presented in tabular form. Full corrections for scattered light and seeing have been included in the reductions. Title: The Solar Spectrum Between .3 and 10 μm Authors: Pierce, A. K.; Allen, R. G. Bibcode: 1977soiv.conf..169P Altcode: No abstract at ADS Title: Kitt Peak 60-cm vacuum telescope Authors: Livingston, W. C.; Harvey, J.; Pierce, A. K.; Schrage, D.; Gillespie, B.; Simmons, J.; Slaughter, C. Bibcode: 1976ApOpt..15...33L Altcode: A major new solar-research telescope conceived and built during a time of budget restraint is described. The observation of magnetic and velocity (circulation) field structure on a synoptic basis and with diffraction-limited resolution is the aim. New optical features include the use of oversize mirrors and windows to avoid thermal edge effects and the placement of the coelostat feed outside the vacuum, mainly for economy. The site selected has prevailing winds that clear thermals from these mirrors. Test data in the form of the system MTF and optical transmission, together with examples of full disk magnetograms and photoheliograms, show present performance capability. Measured MTF indicates a response of 0.2 at 1 sec of arc (whereas diffraction-limited response would be about 0.8). System transmission, including the accompanying spectrograph, is only 2-3% (wavelength 0.44-1.1 microns). Thus, both the optical quality and efficiency are subject to improvement. Title: The Kitt Peak 60-cm Vacuum Telescope Authors: Pierce, A. K.; Livingston, W. C.; Harvey, J. W.; Schrage, D.; Gillespie, B.; Simmons, J.; Slaughter, C. Bibcode: 1976ApOpt..15...33P Altcode: No abstract at ADS Title: Thorium Comparison Spectrum Authors: Breckinridge, James B.; Pierce, A. Keith; Stoll, Clifford P. Bibcode: 1975ApJS...29...97B Altcode: Wavelengths for approximately 1850 thorium emission lines between 2720 and 8805 A are given. The accuracy of these measures appears to be better than ::i:: 0.001 A. These measures, made from photographic plates taken with the 13 .7-m focal length grating spectrograph at the McMath Solar Telescope at Kitt Peak, are part of work done for the solar wavelength atlas program (Pierce and Breckirridge, Kitt Peak Contributions 559, 1973). We suggest they be used for general stellar and solar comparison wavelengths. Subject headings: line identifications - spectra, laboratory Title: The Kitt Peak table of photographic solar spectrum wavelengths Authors: Pierce, A. Keith; Breckenridge, James B. Bibcode: 1974kptp.book.....P Altcode: No abstract at ADS Title: Radiation and structure of the solar atmosphere (Radiation et structure de l'atmosphère solaire). Authors: Athay, R. G.; Delbouille, L.; Pierce, A. K.; Rigutti, M. Bibcode: 1973IAUTA..15..129A Altcode: No abstract at ADS Title: True Central Intensities of Fraunhofer Lines Authors: Brault, J. W.; Slaughter, C. D.; Pierce, A. K.; Aikens, R. S. Bibcode: 1971SoPh...18..366B Altcode: From observations made at Kitt Peak the true central intensities of 40 Fraunhofer lines distributed between λλ 3083-7699, for the center of the solar disk, are derived and given in tabular form. The paper includes a description of the optical system - telescope and spectrograph. The methods of observation and reduction of the data are discussed. Title: Working Group on Central Line Intensities Authors: Pierce, A. K. Bibcode: 1971IAUTB..14..116P Altcode: No abstract at ADS Title: Working Group on Sunspot Spectra Authors: Pierce, A. K. Bibcode: 1971IAUTB..14..115P Altcode: No abstract at ADS Title: Radiation and structure of the solar atmosphere. Authors: Athay, R. G.; Pierce, A. K.; Rigutti, M. Bibcode: 1970IAUTA..14..111A Altcode: No abstract at ADS Title: The Solar Wavelength Program-Kitt Peak National Observatory Authors: Brault, J. W.; Breckinridge, J. B.; Pierce, A. K. Bibcode: 1969BAAS....1Q.235B Altcode: No abstract at ADS Title: The Solar Program of the Kitt Peak National Observatory Authors: Pierce, A. Keith Bibcode: 1969SoPh....6..498P Altcode: No abstract at ADS Title: The Chromospheric Spectrum Outside of Eclipse, lambda lambda 304O to 9266 A Authors: Pierce, A. Keith Bibcode: 1968ApJS...17....1P Altcode: Approximately 11500 chromospheric emission lines are listed from plates taken at the McMath solar telescope with the slit of the spectrograph placed tangent to the limb of the Sun. The ledger gives (1) solar wavelengths, (2) rough eye estimates of intensity, (3) identifications for both atomic and molecular lines, (4) laboratory wavelengths, and (5) multiplet numbers. A brief discussion of selected elements and lines is given in the text. Title: Energy from the Sun. (Book Reviews: Solar Radiation) Authors: Pierce, A. Keith Bibcode: 1966Sci...154..639R Altcode: No abstract at ADS Title: Report of the Working Group on Central Line Intensities Authors: Pierce, A. K. Bibcode: 1966IAUTB..12..169P Altcode: No abstract at ADS Title: Grinding and Figuring Equipment Authors: Pierce, A. K. Bibcode: 1966IAUS...27...75P Altcode: No abstract at ADS Title: Construction of a Bowen Image Slicer Authors: Pierce, A. Keith Bibcode: 1965PASP...77..216P Altcode: No abstract at ADS Title: Observations of the Flash Spectrum Outside Eclipse Authors: Pierce, A. K. Bibcode: 1965PASP...77..137P Altcode: No abstract at ADS Title: The Infrared Spectrum of the Sun Authors: Pierce, A. Keith Bibcode: 1965ASPL....9..217P Altcode: 1965ASPL..428.....P No abstract at ADS Title: The McMath solar telescope of Kitt Peak National Observatory Authors: Pierce, A. Keith Bibcode: 1964ApOpt...3.1337P Altcode: Available from http://www.opticsInfoBase.org/abstract.cfm?id=13580; Title: Excitation-Temperature Equality in the Balmer Lines. Authors: Pierce, A. Keith; Waddell, J., III Bibcode: 1964ApJ...140.1160P Altcode: An analysis of observations of the Balmer lines suggest that the excitation temperatures of these lines are equal, to within present observational error. Title: The Coronal Spectrum of the July 20, 1963 Eclipse Authors: Pierce, A. Keith; Slaughter, Charles D. Bibcode: 1963PASP...75..459P Altcode: No abstract at ADS Title: Report of scientific sessions Authors: Pierce, A. K. Bibcode: 1962IAUTB..11..316P Altcode: No abstract at ADS Title: Analysis of Limb Darkening Observations Authors: Pierce, A. K.; Waddell, J. H. Bibcode: 1961MmRAS..68...89P Altcode: 1961MmRAS..63...89P No abstract at ADS Title: The Large Solar Telescope at Kitt Peak II Authors: McMath, Robert R.; Pierce, A. Keith Bibcode: 1960S&T....20..132M Altcode: No abstract at ADS Title: The Large Solar Telescope at Kitt Peak, II Authors: Pierce, A. K.; McMath, R. R. Bibcode: 1960S&T....20..132P Altcode: No abstract at ADS Title: The Large Solar Telescope at Kitt Peak I Authors: McMath, Robert R.; Pierce, A. Keith Bibcode: 1960S&T....20...64M Altcode: No abstract at ADS Title: The Large Solar Telescope at Kitt Peak, I Authors: Pierce, A. K.; McMath, R. R. Bibcode: 1960S&T....20...64P Altcode: No abstract at ADS Title: The Photosphere of the Sun. Authors: Goldberg, Leo; Pierce, A. Keith Bibcode: 1959HDP....52....1G Altcode: The continuous spectrum Solar constant Observed limb darkening Observed solar energy distribution Observational models of the photosphere The Fraunhofer spectrum Observational data The formation of Fraunhofer lines The analysis of Fraunhofer lines General references Title: The Photosphere of the Sun Authors: Pierce, A. K.; Goldberg, L. Bibcode: 1958HDA....52....1P Altcode: No abstract at ADS Title: Performance of an Eight-Inch Babcock Grating in a Large Vacuum spectrograph Authors: Pierce, A. K. Bibcode: 1957JOSA...47....7P Altcode: 1957OSAJ...47....7P No abstract at ADS Title: A High-Resolution Isophotometer. Authors: Mohler, O. C.; Pierce, A. K. Bibcode: 1957ApJ...125..285M Altcode: A modification of a microdensitometer that converts the instrument into an isophotometer is described. There are two advantages of the modified instrument. First, it is completely automatic in operation; second, the accuracy of the intensity levels can be made very high Title: Preliminary Results with a Vacuum Solar Spectrograph. Authors: McMath, Robert R.; Mohler, Orren C.; Pierce, A. Keith; Goldberg, Leo Bibcode: 1956ApJ...124....1M Altcode: New observations of the solar spectrum with a high-resolution vacuum spectrograph reveal a wealth of detail in the cores of all Fraunhofer lines observed both in the normal disk and in areas exhibiting various kinds of solar activity. The lines show fluctuations in width, intensity, and position over intervals as small as 2 seconds of arc. A representative collection of photographs is presented, together with tentative conclusions derived from inspection and preliminary measurement. Measurements of Doppler shifts have been carried out in considerable detail for the two lines Cr X 4626 and Ba+ X 5853. The random turbulent velocity at the center of the disk is 0 70 km/sec for the chromium line and O. km/sec for the ionized barium line. For both lines the random turbulent velocity appears to increase toward the limb. The velocity shifts observed for the Ha and sodium D lines are of the same order of magnitude as those of the weaker metallic lines. The disk observations of the Fraunhofer lines of hydrogen and ionized calcium seem to he consistent with a qualitative model of the low chromosphere, consisting of relatively hot clouds of gas and with cooler regions both above and between the hot regions. Both the K2 emission in ionized calcium and the wide absorption features in Ha seem to originate in the hot regions; from the appearance of these line features near the limb it seems that the hot regions contribute a substantial fraction of the hydrogen and ionized calcium emission in the very low chromosphere. The profiles of Ha at the extreme limb and of the K line and other strong metallic lines on the disk favor the conclusion of Adams and Burwell that central self-reversal is a general characteristic of most strong chromospheric profiles. The similarity between the intensity and velocity fluctuations in the core of the strong magnesium line X 5167 and in those of neighboring weaker lines implies either a chromospheric origin for the centers of these weaker lines or the extension of the photospheric granules into the low chromosphere. The preliminary nature of the foregoing results is emphasized. Title: Doppler Shifts in Solar Granules. Authors: McMath, Robert R.; Mohler, Orren C.; Pierce, A. Keith Bibcode: 1955ApJ...122..565M Altcode: No abstract at ADS Title: Introductory remarks: Some Observational Techniques and Basic Data on Stellar Atmospheres Authors: Pierce, A. Keith Bibcode: 1955stat.conf....1P Altcode: 1954stat.conf....1P No abstract at ADS Title: Solar Limb Darkening in the Region λλ 7793-24388. Authors: Pierce, A. Keith Bibcode: 1954ApJ...120..221P Altcode: Observed values of limb darkening determined with a PbS cell and the Snow telescope of the Mount Wilson Observatory are given for the near infrared. The method of correcting the observed curves for seeing, scattered light, and time constant is given in detail. The observed brightness distribution extends from cos 0 = 1.00 to cos 6 = 0.10; and covers the interval XX 7793-24388 with values at 26 different wave lengths. Title: Photoelectric Observations of the Profile of HA in the Sun's Spectrum. Authors: Pierce, A. Keith Bibcode: 1954ApJ...120..233P Altcode: The profile of Ha in the sun's spectrum for the center of the disk is tabulated. The wings of the line show a depression of 1 per cent at 4 40 A from the line center. The central core of the line is asymmetrical with the minimum intensity at -0.037 A. Title: The profile of Hα in the sun's spectrum. Authors: Pierce, A. Keith Bibcode: 1954AJ.....59..189P Altcode: The existing infrared equipment of the McMath-Hulbert Observatory has recently been modified so that direct scanning of the visible spectrum with a I P2 I photomultiplier can be carried out. Through the kindness of Dr. I. Bowen we have been able to use a 6 X 8 inch, 15,000 g/inch grating ruled by Babcock. Tracings made in the green of the fourth order show a resolution in excess of 250,000. But, because of the low sensitivity of the I P2 I at Ha, wider slits were used so that R = 150,000 for these observations. The grating has negligible scattered light while the total ghost intensity is 2.0 per cent in the fourth order. The position of the continuum and extent of the wings of Ha were determined from tracings covering 200 to 300A in length. Observations made at the sun's center show a measurable depression of one per cent occurring at 40A from the line center. The Doppler core of the line was observed at cos 6 = 1.00, o.86, 0.64, 0.42 and 0.25. At cos 0 = 1.0, the central parts of the line show a distinct asymmetry in the direction that the red part is considerably more rounded on the bottom than the violet. The minimum of intensity occurs at -0.042A. At this point there often appears a sharp, weak absorption line. The strongest absorption feature so far observed has an equivalent width of 0.0036A, which corresponds to 1.5 X 1010 atoms in the second quantum level. The sharpness of the feature, a half-width about 0. IA, implies the unreasonably low temperature, ~oo0K, particularly since the hyperfine structure amounting to a separation of components of 0.12A should appear. Hence its interpretation as hydrogen absorption is uncertain. The absorption feature and the asymmetry of the line disappear at the limb. The general asymmetry of the line can be explained if we assume a complex emission core produced by jets or small prominences, some having a radial velocity of 5 km/sec toward the sun and others with a velocity of 8 km/sec outward from the sun. In a general way this agrees with the H2, K2 emission in Ca. T. Royds observed on Ha spectroheliograms that dark markings and the bright emission markings accompanying spot disturbances showed best when the second slit of the spectroheliograph was set 0.2A to the violet.' When the slit was set to the red it was observed that the markings disappear and the image is much less contrasty. Further observations will be made on the relationship of the line profile to spectroheliograms. Title: Relative Solar Energy Distribution in the Spectral Region 10,000-25,000 a. Authors: Pierce, A. Keith Bibcode: 1954ApJ...119..312P Altcode: Tables are given of the observed relative solar energy distribution for zero air mass in the wavelength interval 10,()()( 25,000 A. The observations are based on measures made at Mount Wilson at the Snow telescope with resolution-band pass 0.30 A. The calibration of the spectral response of the equlpment was evaluated by observations of a black-body source and a pyrometric arc. A detailed description of the comparison sources and their use is given. Title: The 50-foot focal length vacuum spectrograph for solar research. Authors: McMath, R. R.; Mohler, O. C.; Pierce, A. K. Bibcode: 1954AJ.....59R.328M Altcode: It is plain that an adequate study of the profiles of a large number of Fraunhofer lines demands a spectrograph of high resolving power and great linear dispersion. Through the kindness of Drs. I. S. Bowen and H. W. Babcock we have been able to use one of their fine gratings, 6X8 inches, in our Pfund system.' With this arrangement we immediately found an asymmetry and variable features in the center of Ha.2 However, further work on faint solar lines and on the absorption spectrum of iodine indicated a resolving power lower than anticipated with this particular grating. Photoelectric traces made by placing the steep portion of an absorption line or the very steep intensity change at the zero order on the exit slit of the spectrometer indicated from the strong random fluctuations of the signal that spectrographic seeing was the undoubted cause of lowered resolution. For photographic work the criteria for the design of large stellar spectrographs, as given by I. S. Bowen,3 require that the resolving power of the photographic plate be matched to the linear resolving power of the grating at the focal plane. A photograph taken with a spectrograph approximating this condition will show considerable graininess if a narrow slit of width equal to the resolving power is used in the photometer. Where there is ample light the use of a longer focal length and a larger scale permits the use of wider microphotometer slits with a gain in smoothness of the recording with no loss in resolving power. In addition, with the larger scale spectrograph the slits are mechanically easier to construct and the effects of dust, defects and non- parallelism of the slit jaws are percentagewise less. The latter points are of considerable importance in problems which involve photometry of details of the solar surface that the slit intersects along its length. However, a longer focal length aggravates the seeing problem. Following the high resolution work on Ha and an experimental investigation of our spectrographic seeing, both at Lake Angelus and at the Snow telescope at Mount Wilson, Dr. McMath started in January 1954 the design and construction of a large vacuum spectrograph which would completely eliminate the spectrograph seeing problem, and which would give adequate scale and vacuum wave lengths. The design utilizes the 50-foot focal length off-axis mirror system of the existing McGregor Tower to form an image of the sun at the first slit of a predisperser before the grating spectrograph. The optical arrangement of the spectrograph follows the design described by M. Czerny and A. F. Turner,4 but the mirrors and grating are now placed in a vacuum tube 52 feet long and 4 feet internal diameter. Other tube specifications are: Rolled and welded plate, thickness ~` inch, reinforced with rings every four feet. The end plates are 14' inches thick and are heavily reinforced with 6-inch deep ribs of i-inch plate welded to the inside faces. Light from the entrance slit located behind a quartz field lens which also acts as a window to the vacuum tank is collimated by a i~-inch spherical mirror and returned to the grating located several feet inside the head of the tube. The dispersed beam is focused on the second slit by a second i~-inch spherical mirror and after passing through a quartz window is received by a photomultiplier. A third concave i~-inch mirror at the far end of the tube is arranged so that a short region of the spectrum can be returned to a photographic plate. All mirrors, and the grating table, are provided with complete motions in all degrees of freedom through the use of electrical motors. The final adjustments can be made by push buttons after the tank has been pumped down and assumed its slightly altered shape under the atmosphere pressure load of 700 tons. The head of the spectrograph is to be provided with air locks at every point. The adjustment and repair of the slits,: or of the photocell, are thus facilitated without destroying the vacuum of the main tank. A special cassette and air lock will permit a quick plate change to be made. The tank, constructed by Whitehead and Kales of Detroit, proved to be vacuum-tight on erection. The first pump-down with a Kinney vacuum pump, Model VSD-88i I, of 45 cubic feet displacement per minute, required one hour to reach I cm pressure I mm after two hours. A pressure of 70 microns has been obtained and it is expected that still lower values will be achieved after the inside surfaces, painted with red lead, have occluded their more volatile constituents. Tests have shown that the rate of pressure rise on the tank is so small, 0.1 mm rise per 24 hours, that it will be possible to pump out the tank at night and then to shut off the pump during the operating day. This is a necessary requirement as the pump, though on an isolated pier with flexible connection to the tank, carries a perceptible vibration to the optics. This spectrograph will allow the use of one of Babcock's superb gratings in the fifth order, and should allow the grating to develop its full resolving power of about 600,000. The linear dispersion in the fifth order will be 6.92 mm per angstrom at 5000 A. This dispersion should make3]possible faint line profile work containing a relatively small instrumental contribution. The scattered light is to be evaluated by interferometric and other methods. Precision measurements of profiles of the stronger lines by photoelectric methods requires an exceptional sky. Our experience has been that sky transparency over long intervals of time is so rarely obtained that means of monitoring the background intensity is very desirable. For this purpose we are planning to use a modification of the system employed by Hiltner and Code.5 One photocell will monitor a 200 A interval as passed by the predisperser through the first slit, and the other will record the spectrum through the second slit. Reflecting slits of stellite will allow one to guide accurately on details seen through a Lyot filter which will present a field bisected by the slit. 5.R. R. McMath and 0. C. Mohler, J. Opt. Soc. Amer. 39, 903, `949. 2.Ap. J. in press. 3.Ap. J. is6, 5, 5952. 4.Zs. Phys. 6i, 792, 5930. 5.J. Opt. Soc. Amer. 40, `49, 5950. McMath-Hulbert Observatory, University of Michigan, Pontiac, Mich. Title: Table of Infrared Solar Lines, 1.4-2.5 μ. Authors: Mohler, Orren C.; Pierce, A. Keith; McMath, Robert R.; Goldberg, Leo Bibcode: 1953ApJ...117...41M Altcode: Accurate wave lengths and measurements of equivalent width are given for 888 solar lines in the spectral region 1. 2.5 . The number of solar lines has been more than doubled, as compared with previous preliminary studies in this spectral region. The wave lengths of the solar lines are referred to those of the Fraunhofer lines in the visible and very near infrared spectrum by the method of overlapping orders. The root-mean-square errors of the infrared standard wave lengths, as derived from repeated measurements of individual lines, are +0.13 A for the l.6 region and +0.17 A for the 2.3 region. The equivalent widths are preliminary. The estimated errors are between 10 and 100 per cent, depending upon the degree of blending. About 470 infrared solar lines have been tentatively identified with atoms of H, K, C, At, Na, Si, Mg, Ca, Ni, and Fe and with first overtone lines of CO. Comparisons between solar wave lengths and those measured in the laboratory or predicted from term values reveal somewhat closer agreement, on the average, between the solar and the predicted values than between the solar and the laboratory values. Title: Model Solar Atmospheres. Authors: Aller, Lawrence H.; Pierce, A. Keith Bibcode: 1952ApJ...116..176A Altcode: An iteration method is described for obtaining model stellar atmospheres when the temperature as a function of optical depth is known. This process is applied to the solar atmosphere, using an empirical temperature distribution based on observations of limb darkening. The total pressure, the electron pressure, and the absorption coefficient are tabulated as functions of the optical depth for different hydrogento-metal ratios. In addition, two solar models with He/H ratios of and are tabulated and compared with other models. Title: The Abundance of CO in the Sun and in the Earth's Atmosphere Authors: Goldberg, Leo; McMath, Robert R.; Mohler, Orren C.; Pierce, A. Keith Bibcode: 1952PhRv...85..481G Altcode: No abstract at ADS Title: Identification of CO in the Solar Atmosphere Authors: Pierce, A. K.; Goldberg, L.; McMath, R. R.; Mohler, O. C. Bibcode: 1952PhRv...85..140P Altcode: No abstract at ADS Title: The Abundance of CO in the Sun and in the Earth's Atmosphere Authors: Pierce, A. K.; Goldberg, L.; McMath, R. R.; Mohler, O. C. Bibcode: 1952PhRv...85..418P Altcode: No abstract at ADS Title: The Structure of the Solar Atmosphere as Deduced from Limb-Darkening Measures. Authors: Pierce, A. Keith; Aller, Lawrence H. Bibcode: 1951ApJ...114..145P Altcode: From solar limb-darkening measurements made at the McMath-Hulbert Observatory and from the intensity distribution at the center of the disk the temperature at optical depth, rX, is derived for a number of wave lengths. The theoretical kx, based on the negative hydrogen ion as the main source of opacity, appears to give an adequate interpretation of the solar limb-darkening measurements in the visual and infrared region of the solar spectrum. The boundary temperature of the sun is about 45000. Title: Solar spectroscopy with echelles. Authors: Pierce, A. Keith; McMath, Robert R.; Mohler, Orren Bibcode: 1951AJ.....56R.137P Altcode: The echelle grating has the advantage of compressing a large spectral range into a small angle about the blaze direction. A 150 X 75 mm echelle has been installed at the McMath-Hulbert Observatory in an optical system using 14-foot focal length concave mirrors for collimator and camera. The observed resolving power at N5000 is about 250,000 with plate dispersion 2.9 mm/A. The instrumental profile shows a narrow central peak with a strong satellite line at about .o5A from the central peak. Photographs of the solar spectrum, prominence spectra, and of a Zeeman triplet in a sunspot magnetic field have been made. McMath-Hulbert Observatory, University of Michigan, Pontiac, Mich. Title: Structure of the solar atmosphere from limb darkening measures. Authors: Pierce, A. Keith; Aller, Lawrence H. Bibcode: 1950AJ.....55..181P Altcode: The darkening to the limb of the sun depends not only on the temperature gradient but also on the absorptivity of the solar gases. From measures of the intensity distribution, A (o), at the center of the solar disk and from limb darkening measures it is possible to derive both the temperature gradient and the wave-length dependence of the absorption coefficient of the solar atmosphere. For this purpose we have utilized Mulders's determination of A (o), together with limb darkening measures made with the lead sulfide cell at the McMath-Hulbert Observatory. The limb darkening curves were made at 10 different wave lengths in the region 0.5 ~ to 2.3 ~ and cover 98.5 per cent of the solar radius. The results confirm previous studies which show that the negative hydrogen ion is the princi pal source of continuous absorption. The extrapolation of the limb darkening curves to the boundary is small and thus a reliable boundary temperature can be found. The observed parts fit a Planck distribution corresponding to a boundary temperature of 45000K with an uncertainty of less than 1000K. From these studies we hope to obtain Improved knowledge of the variation of temperature, gas pressure, electron pressure, etc. with depth and thus finally an improved model of the solar atmosphere. McMath-Hulbert Observatory, University of Michigan, Lake Angelus, Pontiac, Mich. Title: Observations of Solar Limb Darkening Between 0.5 and 10.2&mu Authors: Pierce, A. K.; McMath, R. R.; Goldberg, Leo; Mohler, O. C. Bibcode: 1950ApJ...112..289P Altcode: Measurements of solar limb darkening are tabulated for thirteen wave lengths between 0.5 and 10.2 . Observations in the wave-length region 0.5-2.2 were carried out with the McGregor Tower telescope and spectrometer for the interval cos 0 = 1.0 to cos 0 = 0.16. Measurements at three longer wave lengths were made with a Perkin-Elmer spectrometer attached to the 24inch reflector and covered the interval cos 0 = 1.0 to cos 0 = 0.2. At certain wave lengths the near infrared measurements agree with those of Abbot's to within 0.1 per cent; at other wave lengths the systematic differences are as large as 1 per cent. It is found that the degree of limb darkening decreases in the infrared from 3.5 to 10.2 . This result is qualitatively consistent with a systematic increase of the solar continuous opacity toward longer wave lengths in the infrared, as predicted by theoretical calculations of the absorption coefficient of the negative hydrogen ion. Title: New Solar Lines in the Spectral Region 1.97-2.49 μ. Authors: Goldberg, Leo; Mohler, Orren C.; Pierce, A. Keith; McMath, Robert R. Bibcode: 1950ApJ...111..565G Altcode: Measurements of wave length and of percentage central absorption are given for 109 solar lines in the region 1.97-2.49 of the infrared solar spectrum. The lines were found on tracings obtained with the high-dispersion spectrometers and Cashman PbS cells of the McMath-Hulbert Observatory at Lake Angelus and at the Mount Wilson Observatory. Forty-seven lines have been identified as arising from neutral atoms of H, Na, Si, Mg, Al, Ca, and Fe. The relative scarcity of solar lines in the 2.2 IL region is discussed, and a qualitative explanation is given in terms of the variation with wave length of the continuous absorption coefficient of H- combined with the solar temperature gradient. Title: The 3n3 Band of Telluric CO2 in the Solar Spectrum Authors: Pierce, A. K.; Goldberg, L.; Mohler, O. C.; McMath, R. R. Bibcode: 1950PhRv...78...74P Altcode: No abstract at ADS Title: N2O Bands in the Solar Spectrum Authors: Pierce, A. K.; McMath, R. R.; Mohler, O. C.; Goldberg, L.; Donovan, R. A. Bibcode: 1950PhRv...78...65P Altcode: No abstract at ADS Title: An Improved Tracing of the Solar Spectrum Between 2. 9 and 3. 6 Microns Authors: Mohler, Orren; Pierce, A. Keith Bibcode: 1949PASP...61..221M Altcode: No abstract at ADS Title: Solar Observations with a Perkin-Elmer Infrared Spectrometer Authors: Pierce, A. Keith Bibcode: 1949PASP...61..217P Altcode: No abstract at ADS Title: Note on Methane in the Infra-Red Solar Spectrum Authors: Pierce, A. K.; McMath, R. R.; Mohler, O. C.; Goldberg, L. Bibcode: 1949PhRv...76.1533P Altcode: No abstract at ADS Title: Carbon Dioxide in the Infra-Red Solar Spectrum Authors: Pierce, A. K.; Goldberg, L.; Mohler, O. C.; McMath, R. R. Bibcode: 1949PhRv...76.1848P Altcode: No abstract at ADS Title: The solar curve of growth and the kinetic temperature of the solar reversing layer. Authors: Pierce, A. Keith; Goldberg, Leo Bibcode: 1948AJ.....53..202P Altcode: An observational solar curve of growth for iron, titanium, and vanadium was constructed from the gf values of the Kings and the equivalent widths of Allen. Corrections for the variable continuous opacity and limb darkening coefficient were applied to each line before grouping according to excitation potential. For iron and titanium the displacement of the groups gave a temperature of 46800 K, while for vanadium no proper temperature could be found because of the non-linear relation between excitation potential and the displacements. The observed curve of growth was fitted to a theoretical curve based on the Milne-Eddington model. The "best" fit corresponds to a most probable Doppler velocity of 2.5 km/sec and values AND/AXN = a (as defined by Mitchell and Zemansky, Resonance Radiation and Excited Atoms, Cambridge, 1934) equalling 0.01 for the weaker iron lines and 0.05 for the stronger. The velocity parameter may be interpreted in terms of either a kinetic temperature of 57000 plus a turbulent velocity of 2.0 km/sec or a straight kinetic temperature of 19,5000 K. In an attempt to distinguish between the alternatives of thermal or turbulent broadening, the half-widths of faint lines of several elements of different atomic weight, ranging from carbon to nickel, were determined from the Utrecht Atlas. The widths of these lines, after correction for instrumental broadening, show a dependence on atomic weight that accords well with the assumption of thermal widening at a temperature of 16,0000 K. Observatory, University of Michigan, Ann Arbor, Mich. Title: Mass Spectrographic Confirmation of the Isotopic Assignment for the Long-Lived Radioactivity in Beryllium Authors: Pierce, A. K.; Brown, F. W. Bibcode: 1946PhRv...70..779P Altcode: No abstract at ADS