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NASA NTRS1976

Photoelectric photometry of comet Kohoutek (1973f)

Comet Kohoutek was observed with the 50 cm (f/15) reflecting telescope of the European Southern Observatory, La Silla, Chile, on fourteen nights between January 16 and 30, when the heliocentric and geocentric distances of the comet were r=0.66 - 1.00 A.U. and delta=0.81 - 0.96 A.U., respectively. The 40 inch and 80 inch diaphragms were used for the photometry of the cometary head in the UBV system and with six interference filters. The atmospheric conditions were good but the accuracy of observations was low due to large extinction and twilight. The mean error of one measurement of log F in all but Na 5893 A filters can be estimated at plus or minus 0.02, whereas the accuracy through the Na filter was substantially lower.

Kohoutek, L.↗
NASA NTRS1978

Photoelectric photometry of J V

UBV photometry of J V (Amalthea) near greatest western elongation shows this satellite to be about one magnitude fainter than previously believed. It is observed to be very red, having a B-V color index near + 1.5 mag. Unlike the Galilean satellites, J V appears to be a low-albedo object.

Millis, R. L.↗
NASA NTRS1982

Photoelectric photometry of asteroids 33 Polyhymnia and 386 Siegena

The photometric parameters of 33 Polyhymnia and 386 Siegena were determined in the course of an international campaign performed during August 15-September 14, 1980 at Table Mountain Observatory, European Southern Observatory, and Catania Astrophysical Observatory. The rotational periods and amplitudes were determined, and the multiple-scattering factor was found to be 0.15 plus or minus 0.06 for 386 and 0.26 plus or minus 0.33 for 33, implying higher albedos in each case than expected according to their taxonomic classes, C and S, respectively. The color indices B-V and U-B were measured and found to differ significantly from those given by Bowell et al. (1979).

Zappala, V.↗
NASA NTRS1983

Photoelectric photometry of selected SAO stars. III

Photometric observations of 131 SAO stars for use in calibrating data obtained from the Near Infrared Photographic Sky Survey (NIPSS) are reported. The serial numbers of the primary NIPSS program fields in which the photometry was done are shown along with the approximate position of each field and the number of stars observed in each field. The observations are listed, showing the SAO numbers of the program stars, their 1950 equatorial coordinates, the V magnitudes, and the (V-R) and (V-I) color indices. The mean errors in magnitudes and color indices obtained by averaging deviations from the mean for each star are on the order of 0.02 mag.

Scharlach, W. W. G.↗
NASA NTRS1985

Photoelectric photometry of asteroid 69 Hesperia

UBV photometric observations of the M asteroid 69 Hesperia, obtained using single-channel photometers on the 31-in. and 42-in. reflectors at Lowell Observatory and on the 24-in. reflector at Mauna Kea Observatory during the apparition of August-November 1977, are reported. The data are presented in tables and graphs and analyzed. Findings presented include minimal temporal or phase-angle-dependent light-curve fluctuations, evidence for large-scale albedo variegation of a few percent, synodic rotation period 5.65537 + or - 0.00064 h, zero-phase color indices B-V = 0.68 mag and U-B = 0.24 mag, B-V phase reddening 0.003 mag/deg, and absolute zero-phase primary maximum magnitude V = 7.04.

Poutanen, M.↗
NASA NTRS1989

Photoelectric photometry of the RS CVn binary EI Eridani = HD 26337

Differential UBV(RI)sub KC and UBVRI photometry of the RS CVn binary EI Eridani obtained during December 1987 and January 1988 at fourteen different observatories is presented. A combined visual bandpass light curve, corrected for systematic errors of different observatories, utilizes the photometric period of 1,945 days to produce useful results. The analysis shows the visual light curve to have twin maxima, separated by about 0.4 phase, and a full amplitude of approximately 0.06 mag for the period of observation, a smaller amplitude than reported in the past. The decrease in amplitude may be due to a decrease or homogenization of spot coverage. To fit the asymmetrical light curve, a starspot model would have to employ at least two spotted regions separated in longitude.

Hooten, J. T.↗
NASA NTRS1985

Photometric support for future astonomical research

The I.A.P.P.P. is described and how that organization can provide photometric support for future astronomical research projects such as the 1982-1984 eclipse of epsilon Aurigae discussed at this workshop. I.A.P.P.P., International Amateur-Professional Photoelectric Photometry, is an organization founded in Fairborn, Ohio by the authors in 1980. Its purpose is to encourage contact between amateur and professional astronomers interested in photoelectric photometry, for their mutual benefit and for the benefit of astronomical research. Aspects dealt with include instrumentation, electronics, computer hardware and software, observing techniques, data reduction, and observing programs. Starting with the June 1980 issue, I.A.P.P.P. has published the quarterly I.A.P.P.P. Communications. The Communications contain articles dealing with all the above aspects of photoelectric photometry, although it does not publish observational results as such. Photoelectric photometry obtained by amateurs is published in the same journals which publish photometry obtained by professionals.

Hall, D. S.↗
NASA NTRS1991

Asteroid photometry

Photoelectric light curves provide fundamental information about asteroids: rotation periods, pole orientations, shapes, and phase relations, which yield some information about the surface physical properties. This task is to carry on a program of such observations to increase the overall data base, obtain data on newly discovered asteroids, and to observe asteroids which are the subject of other complementary observations, such as occultations, radar, and infrared.

Harris, Alan W.↗
NASA NTRS1983

Five years of photometry of Lambda Andromedae

Photoelectric photometry of the bright variable RS CVn-type binary Lambda And obtained in 1977-78 and 1980-81 is presented and used, together with earlier photometry, to derive the photometric period and discuss the changing shape of the light curve. The best ephemeris for times of minimum light is 2443829.2 + 53.95 d E. Because times of minimum and maximum extending back to those of Calder in 1933-37 can be phased together properly, the principal dark region must have maintained its identity for almost 50 yr. Over the last five years the brightness range has been between 3.70 and 4.05 m. During 1980-81 shallow secondary minima developed at phases where maxima occurred in previous years. Lambda And remains the only well-established case of nonsynchronous rotation among the known RS CVn variables.

Boyd, R. W.↗
NASA NTRS1984

Ground-based Measurements of Solar Irradiance Variations

Observations and analysis programs being carried out at the San Fernando Observatory are reviewed. A digital analysis of sunspot areas from full disk photographs shows an especially good correlation with areas published in the Solar Geophysical Data Bulletin with scale factor near unity. Results are presented from photoelectric photometry of active regions using the Extreme Limb Photometer. These results suggest energy balance between sunspots and faculae. Preliminary results are presented from a new program of photoelectric photometry using a linear array of diodes. Results are presented for the August 1982 passage of a large active region. This active region caused a maximum dip in the quiet Sun irradiance of about 800 parts per million.

Chapman, G. A.↗
NASA NTRS1970

Photometry of asteroids

Photographic and photoelectric photometry of asteroids, discussing luminescence, reflectivities, light curves, colors and phase variations observations

Gehrels, T.↗
NASA NTRS1976

Physical properties of asteroids from UBV photometry

A program of asteroid photoelectric photometry is discussed which is designed primarily to obtain UBV magnitudes and colors of most asteroids reaching magnitude 13.3 or brighter at opposition and of asteroids reaching magnitude 14.3 or brighter at perihelic opposition. A two-color plot is presented for asteroids whose compositional classes have been determined by radiometry, spectrophotometry, and polarimetry. A clear separation by color is observed for S and C objects; M and E objects are shown to be colorimetrically similar to C objects. Another two-color plot for about 200 asteroids reveals a continuum between the C and M, E domains and a possible continuum between the C and S domains. A plot of the frequency distribution of asteroid semimajor axes indicates that C objects predominate in the outer part of the asteroid belt while S objects are more numerous in the inner part. Statistics of asteroid phase angles and light-curve amplitudes are examined. It is suggested that the phase coefficient of an asteroid is inversely proportional to its geometric albedo and that S objects may be less spherical than C objects.

Bowell, E.↗
NASA NTRS1990

Some Insights on Solar Variability from Precision Stellar Astronomical Photometry

At Lowell Observatory, precision photoelectric photometry was directed toward the study of solar variability and the variability of sun-like stars beginning in 1949 and continuing until now. The ubiquity and range of low-level variability, including some that appears to be cyclic, among solar-type stars shows that recent solar variability may be unusual only in its present restraint.

Lockwood, G. W.↗
NASA NTRS1993

The quality of photometric information in the Hipparcos Input Catalog

Comparison with independent photoelectric photometry is used to assess the quality of magnitudes and colors in the Hipparcos Input Catalog. These magnitudes and colors will play an important role in the luminosity calibration of Hipparcos stars. We conclude that photoelectric photometry, available for about 37 percent of the catalog, is of uniformly good quality, and the error estimates in the Catalog are very accurate. On the other hand, colors determined from poor spectral classes suffer from very significant errors, also correctly estimated in the Catalog, which make them essentially unsuited for the purpose of luminosity calibration. Only stars with either photoelectric colors or good 2D spectral classes can be used in a high-accuracy luminosity calibration.

Casertano, Stefano↗
NASA NTRS1984

A Statistical Evaluation of the Limitations of Single-channel Intermediate-band Photoelectric Stellar Photometry

Error distribution in differential photometry for a moving solar system object is investigated. The results of differential photometry of several dozen pairs of planetary comparison stars observed since 1972 are reviewed. Each pair of stars was observed along with the corresponding planet or satellite, typically about ten times during the course of a single apparation lasting about four months. The comparison stars are chosen to bracket the opposition position of the planet, the expected opposition magnitude, and solar color. In practice, this means that the range of spectral type was mid-F to early K, the range of B-Y color was about 0.25 to 0.95 mag, the range of differential magnitude was less than 2 mag but most often less than 1.0 mag, and the difference in declination was typically less than 3 deg. The difference in air mass at meridian transit was usually less than 0.03, and rarely exceeded 0.01. Hence, differential extinction effects are negligible, except under extraordinary conditions.

Lockweed, G. W.↗
NASA NTRS1979

The dwarf spheroidal galaxy in Draco. I - New BV photometry. II - Galactic foreground reddening

BV photoelectric photometry for 39 stars and BV photographic photometry for 514 stars in the field of the Draco dwarf spheroidal galaxy are presented. The color-magnitude diagram for 512 of these field stars is found to display a well-defined red horizontal branch as well as a red giant branch whose observed width is comparable to the accidental photometric error. The results also indicate that a more diffuse sequence of stars lies about 0.1 mag to the blue of the giant branch and that an upper horizontal branch of more massive core helium-burning stars may also be present. The foreground reddening toward Draco is then determined by narrow-band uvby-beta photometry of galactic B-A-F stars.

Stetson, P. B.↗