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Recent-epochs positions and proper motions of nine dwarf carbon star candidates are presented along with finding charts for each object. Measurements are obtained from digitized Palomar Observatory Sky Survey (POSS) and Quik V plate archives at the Space Telescope Science Institute, and from recent CCD images.

Completion of long-term astrometric plate series yields revised results on the orbits and parallaxes. The subdwarf mu Cas seems to be overluminous; the distance of the supergiant epsilon Aur is near 600 pc. The unresolved companion in the red dwarf pair BD +6degree398 is of very low mass, and the companion of BD +67degree552 massive but probably underluminous.

Trigonometric parallaxes for stars in the regions of the binary stars Delta Equulei (HR 8123) and Chi(sup l) Orionis (HR 2047) are derived from data collected with the Multichannel Astrometric Photometer (MAP) and the Thaw Refractor of the University of Pittsburgh's Allegheny Observatory. The weighted mean parallax of all trigonometric studies of delta Equ is now +5.42 +/- 0.93 mas, corresponding to absolute magnitudes of 3.87 +/- 0.04 and 3.95 +/- 0.04 mag, respectively, for the primary and secondary. Using the Popper and Dworetsky orbit we find a photocentric semimajor axis of 2.9 +/- 0.8 mas and individual masses of 1.21 +/- 0.090 and 1.19 +/- 0.088 solar masses, respectively, for the primary and secondary components. The weighted mean trigonometric parallax of all studies of the binary star Chi(sup l) Ori is +111.0 +/- 0.92 mas, implying an absolute visual magnitude for the dominant GO V primary of 4.63 +/- 0.018 mag. The photocentric semimajor axis, derived from a fraction of the orbit, is 96.9 +/- 5.4 mas.

Trigonometric parallaxes for stars in the regions of the variable stars delta Cephei and EV Lacertae are derived from data collected with the Multichannel Astrometric Photometer (MAP) and the Thaw Refractor of the University of Pittsburgh's Allegheny Observatory. The weighted mean parallax of all trigonometric studies of delta Cephei is now + 0.0030 sec + or - 0.00093 sec, corresponding to a distance modulus of 7.61 + or - 0.67 mag. This indicates that this luminosity standard star is approximately one standard deviation more distance than has been generally accepted. The weighted mean trigonometric parallax of all studies of the variable star EV Lacertae (BD + 43 deg 4305) is + 0.1993 sec + or - 0.00093 sec, implying a distance modulus of - 1.498 + or - 0.0010 mag. The calculated absolute magnitude of this star is almost exactly that predicted by its (R-I)(sub Kron) magnitude and by the Gliese (R-I) main-sequence value for stars in the solar neighborhood. We also find a parallax of 0.0189 sec + or - 0.0008 sec for the FO IVn star, HR 8666 (BD + 43 sec 4300). The derived luminosity of this star is midway between that expected for luminosity class IV and V stars at the indicated temperature.

This system consists of three red-dwarf components with masses from 0.4 to 0.1 solar masses. The orbits with periods of 16 and 323 years are rediscussed from astrometric plates to 1991.

We have determined the orbit and parallax of the Procyon system (F5 IV-V primary and white dwarf secondary) using conventional absolute radial velocities, precise relative radial velocities determined with the hydrogen flouride (HF) absorption-cell technique, and astrometric and visual observations. Our least-squares analysis confirms and strengthens Strand's previous analysis based on more limited material. We derive an absolute parallax of piabs=0.2899 ± 0.0074 arcsec. Our parallax result is in excellent agreement with other parallax investigations based on independent material. If we adopt the latest USNO parallax of piabs=0.2864 ± 0.0023 arcsec, then from our orbital paramters we derive MA=1.751 ± 0.051 solar mass, and MB=0.622 ± 0.017 solar mass. For the derived mass of Procyon A (which is consistent with previous results), it has long been known that the luminosity predicted by stellar interior theory is approximately a factor of two larger than the luminosity derived from observations. The errors in this observed luminosity and the above formal standard errors (i.e., our best estimates of the statistical random errors) in our derived mass are too small to explain this discrepancy. If the observed separation of the binary components has been systematically overestimated by approximately 0.2 arcsec, then the derived mass would be reduced, thus resolving the discrepancy. However, the excellent consistency of the separations measured by Aitken and Barnard for a number of years at different sites argues against this interpretation. The stellar interior theory of Procyon A may need substantial revision.

A complete determination is made of the orbital elements of the visual binary Sigma 2173, by combining new high-dispersion spectroscopic observations with others obtained during passage through the opposite node and with visual and interferometric observations. While the derived parallax of 0.059 arcsec implies masses and luminosities for the components that are in good agreement with spectral types and luminosity classes, they are noted to be problematic from the standpoint of extant theoretical studies of stellar evolution. The two stars of this system are so similar that no difference is distinguishable in spectral type; the brighter of the two stars appears, however, to be the less massive.

In this paper the results of a study of the relation between M-giant spectral types and their intrinsic color indices are presented. The result of a discussion of the absolute magnitudes of M-type giants, determined by different authors, is also given. These results will be used for the determination of the space density of M giants in the galactic plane.

A new generation of photoelectric astrometric telescopes promises significant advances for both semiglobal and differential astrometry. Some of these new telescopes have a Ronchi ruling at the prime focal plane. The images move relative to the ruling, behind which photomultipliers or similar detectors view the modulated transmitted light. When several stars are viewed simultaneously, this technique exploits correlations in the atmospheric seeing to significantly improve differential astrometric precision. This article presents some general design and analysis criteria for this type of telescope and describes the particular reflector telescope. This has a 29-cm aperture and has met a 4-milli-arc-second differential precision per 5-minute observation. The system is designed for a program of improved annual parallax and solar-system object measurements.

A determination is made of the spectroscopic parallax of Stock 14 on the basis of an MK classification of the 14 brighter stars. Of these, it is noted that two are spectroscopic nonmembers and one is the supergiant V810 Cen. The mean color excess is found to be E(B-V) = 2.26 m + or - 0.12 kpc (s.e. mean for 11 stars); this is fully consistent with Turner (1982), whose results are based mainly on UBV photometry, and conforms to the slightly evolved main sequences of NGC 3293. The independent determination made here confirms Turner's result, in particular with regard to the absolute magnitude and probable membership of the pseudo-cepheid V810 Cen. The nature of the star as a small-amplitude cepheid, however, is by no means certain.

The paper presents a new parallax, proper motion, and orbit for the 7th magnitude G0 V pair Sigma 1819. The absolute parallax is +0.027 + or - 0.006 arcsec (s.e.). With the newly determined orbital elements (P = 220.0 y, a = 1.117 arcsec) the components are found to be main-sequence stars of equal mass (about 0.74 the solar mass) with absolute magnitudes of 4.7 and 4.8.

Radial velocities measured for both components of 70 Oph during the recent passage of the stars through the nodes of their orbits enable the parallax and mass of the system to be determined independently of absolute astrometric measurements. The absolute parallax derived from radial velocities alone is 0.194 arcmin (+ or - 0.004 arcmin) (if the apparent semiaxis and the period of the orbit are assumed to be given by visual observations). Combining this value with the best astrometric determination yields an absolute parallax of (0.199 arcmin) and individual masses for the stars of 0.81 (+ or - 0.06)solar mass and 0.72 (+ or - 0.09). It is also shown that the new radial-velocity observations agree with the best micrometer measures in providing no evidence for a perturbation in the orbital motion of the brighter star.

A total of 371 photographic plates were made of the binary Mu Cassiopeia (Mu Cas) region with a 76 cm refractor. An astrometric orbit of nearly 22.09 yr was calculated, accompanied by an eccentricity of close to 0.58 and a semimajor axis close to 0.19 arcsec. The absolute magnitude was approximately 5.83 and the radial velocity 164 km/sec.

A technique for estimating trigonometric parallaxes in a matter of days or weeks is presented. The technique relies on the discrepancy between the instantaneous proper motion and the proper motion of a star. The main sources of error in the method are the standard error of the individual observations (0.004 arcsec) and the arbitrary limit placed on the observation interval. The parallactic motion of an MO dwarf of known parallax and a blue magnitude of 11.2 is determined. The slope inferred is within 10 percent of the value (0.555 arcsec) derived from a 1.5-year study of Barnard's star. It is concluded that the technique, if used on the same time scale as conventional techniques, would yield results of much higher accuracy.

Astrometric results for the high-velocity metal-poor G8 subdwarf HR 4550 show a parallax of 0.122 + or -0.004 arcsec. The radial velocity of -98.2 + or -0.2 km/s appears to be constant. The difficulty in obtaining an accurate determination of the secular acceleration of the proper motion is discussed. No evidence for orbital effects of the unconfirmed visual companion of HR 4550 is found in the observations.

Photoelectrically determined color indices of white dwarfs are reviewed with particular emphasis on the possibility that a large percentage of these objects in the solar neighborhood are members of the Hyades and Sirius superclusters. The astrometric, photometric, and spectroscopic data now available for the best-established cases of such membership are discussed. The color-luminosity array obtained from supercluster members is tested against that obtained with trigonometric parallaxes determined at the U.S. Naval Observatory.

We present a new parallax and orbit for the late-type 9th magnitude system ADS 8887. The Sproul absolute parallax is + 0'.'051 :1: 0'.'005 (p.e.); we adopt a combined absolute parallax of 0'.'053 :1: 0'.'004 (p.e.). This absolute parallax, combined with newly derived orbital elements (P = 229.r0, a = 2'.'14), yields a total mass for the system of 1.2 . This appears to resolve a long-standing discrepancy inherent in earlier orbits. No evidence for an unseen third body was found. Key words: parallax-visual binary-orbit

Sproul photographic data covering two periods of revolution for each of these well-known visual binaries provide independent orbital elements. The dynamical elements P,T,e, are 34Y.33, 1933.17, 0.41, respectively, for ζ Her. The corresponding values for 85 Peg are 26Y.27, 1962.52, 0.26. The orientational elements of the apparent orbits are also derived. The Sproul absolute parallax for ζ Her is + 0".091 ± 0".003 (p.e.). The mass found for the system is 2.21 Msun; MA = 1.43 Msun, for the G0 subgiant, and MB = 0.78 Msun. No clear indication of a third body is shown by the residuals. The Sproul absolute parallax for 85 Peg is +0.081 ± 0".003. The mass found for the system is 1.50 Msun; MA = 0.82, MB = 0.68 Msun.

Values and probable errors are reported for the orbital elements, parallax, and proper motion of the G0 V star Chi-1 Ori. An absolute parallax of +0.102 (+ or - 0.002) arcsec is adopted along with a value of 1.00 (+ or - 0.10) solar mass for the A component. A range of masses is given for the B component, and it is suggested that the primary is not a close binary.

Astrometric analysis of plates taken on 36 UMa A with the Sproul 61-cm refractor indicate variable proper motion which can be explained by Kepler motion for a photocentric orbit with a period of 18 years. An unseen red-dwarf companion is indicated with a mass of about 0.07 solar mass. This additional companion makes the 36 UMa system at least quadruple. The Sproul relative parallax of the system is + 0.0738 arscec + or - 0.0028 arcsec as determined by the A component.

The narrow absorption features superimposed on the rotationally broadened Mg II λ4481 line of o And A are almost certainly from the spectrum of o And B which is shown to be a 33.01 day double-lined spectroscopic binary. The speckle interferometrically measured separations of Aa and AB indicate that the system contains at least two doubles separated by some 25 AU with the periods of A-a and Aa-B on the order of four and 30 years, respectively, based on a parallax of 0.015±0.008 arc seconds.

The high quality of the United States Naval Observatory trigonometric parallaxes, and the unique temperature-color relation found for multichannel spectrophotometry permit a detailed reexamination of the relation between color and luminosity, and therefore radius, for white dwarfs. The mean white-dwarf radius is 0.0124 Rsun;, based on theoretical fluxes from hydrogen model atmospheres. The cosmic scatter is about 12% in radius, appreciably less than found in other studies, but it is not zero. The scatter is close to that derived by Koester and Weidemann from surface gravities determined from the Balmer jump in hydrogen atmospheres at log g = 8. The masses lie within the range 0.47 to 0.71 Msun;. The single definitely overluminous white dwarf is EG 11 (0135-05).

Orbital elements are reported for three single-line spectroscopic binaries, HR 2692, HR 3725, and HR 5911, none of which have previously determined orbits. In addition, improved orbital elements are reported for three stars with previously determined orbits of low quality.

The new relative trigonometric parallax of 0.038 j 0'.' 008 has been obtained for the very high- velocity star W851. When reduced to an absolute parallax and averaged with previous values this yields ir = 0.026 j 0.007 and hence a tangential velocity of 360 km sec-5. The calibration of the subdwarf main sequence requires a very uncertain systematic correction, leading to ir (photometric) o': 026. Key words: parallaxes - subdwarfs

The constancy of the speed of light outside the solar system is checked by a technique combining parallax, visual binary, and spectroscopic binary data. A total of ten binary systems are uncovered with parallax errors small enough to correct for systematic errors in distance estimates, which are used to check directly for the speed of light within one standard deviation. The speed is found to be constant to within 10% for distances up to 25 parsecs.

Observations during and after the periastron passage of Castor AB permit a rediscussion of the orbit (P = 467 yr, a = 6.80 arcsec). Also discussed are the motion of star C, parallax, and masses of the sextuple.

This paper is reproduced from Publ. Astron. Soc. Pac., Vol. 28, p. 61 - 69 (1916) to celebrate the centenary of the Publications. See also 004.055.

In Lick Observatory Bulletin, 10, 135, 1922, anew determination of the mean parallax of stars of known proper motion and apparent magnitude was given for stars of spectral classes F, G, K and M. It was found later on1, that the formulae given there have some value even in the prediction of parallaxes for individual stars. It seems therefore desirable to derive the corresponding formulae for stars of spectral classes B and A, especially as it is only in recent years that trustworthy determinations of parallax for the highly luminous and distant stars of these classes have come within reach. It was assumed again that the absolute magnitude is linearly related to the quantity m + 5 -f5 log fi, where m is the apparent magnitude and fi the total annual proper motion, thus : tw+5+51ogw=^*+c(m-f5+51og/t*)or M=a+ c H (H was formerly called MaO