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On the current status of open-cluster parameters
We aim to characterize the current status of knowledge on the accuracyof open-cluster parameters such as the age, reddening and distance.These astrophysical quantities are often used to study the globalcharacteristics of the Milky Way down to the very local stellarphenomena. In general, the errors of these quantities are neglected orset to some kind of heuristic standard value. We attempt to give somerealistic estimates for the accuracy of available cluster parameters byusing the independently derived values published in the literature. Intotal, 6437 individual estimates for 395 open clusters were used in ourstatistical analysis. We discuss the error sources depending ontheoretical as well as observational methods and compare our resultswith those parameters listed in the widely used catalogue by Dias et al.In addition, we establish a list of 72 open clusters with the mostaccurate known parameters which should serve as a standard table in thefuture for testing isochrones and stellar models.
| Kinematics of the Open Cluster System in the Galaxy
Absolute proper motions and radial velocities of 202 open clusters inthe solar neighborhood, which can be used as tracers of the Galacticdisk, are used to investigate the kinematics of the Galaxy in the solarvicinity, including the mean heliocentric velocity components(u1,u2,u3) of the open cluster system,the characteristic velocity dispersions(σ1,σ2,σ3), Oortconstants (A,B) and the large-scale radial motion parameters (C,D) ofthe Galaxy. The results derived from the observational data of propermotions and radial velocities of a subgroup of 117 thin disk young openclusters by means of a maximum likelihood algorithm are:(u1,u2,u3) =(-16.1+/-1.0,-7.9+/-1.4,-10.4+/-1.5) km s-1,(σ1,σ2,σ3) =(17.0+/-0.7,12.2+/-0.9,8.0+/-1.3) km s-1,(A,B) =(14.8+/-1.0,-13.0+/-2.7) km s-1 kpc-1, and (C,D) =(1.5+/-0.7,-1.2+/-1.5) km s-1 k pc-1. A discussionon the results and comparisons with what was obtained by other authorsis given.
| Proper motion determination of open clusters based on the UCAC2 catalogue
We present the kinematics of hundreds of open clusters, based on theUCAC2 Catalogue positions and proper motions. Membership probabilitieswere obtained for the stars in the cluster fields by applying astatistical method uses stellar proper motions. All open clusters withknown distance were investigated, and for 75 clusters this is the firstdetermination of the mean proper motion. The results, including the DSSimages of the cluster's fields with the kinematic members marked, areincorporated in the Open Clusters Catalogue supported on line by ourgroup.
| Washington photometry of open cluster giants: two moderately metal-poor anticentre clusters
New photometric data in the Washington system are presented for redgiant candidates in NGC 1817 and 2251, two open clusters located towardsthe Galactic anticentre direction. In the case of NGC 2251, theWashington data are supplemented with new UBV and David DunlapObservatory (DDO) photoelectric photometry. Published radial velocitiesare used to separate field stars from cluster giants. The photometricdata yield an effective temperature and metal abundance for each clustermember. Five independent Washington abundance indices yield meanmetallicities of [Fe/H]= 0.25 +/- 0.04 for NGC 1817 and 2251,respectively. From combined BV and DDO data, we also derive E(B-V) =0.21 +/- 0.03 and [Fe/H]DDO=-0.14 +/- 0.05 for NGC 2251. Bothobjects are then found to be on the metal-poor side of the distributionof open clusters, their metallicities being compatible with theexistence of a radial abundance gradient in the disc. Using the WEBDAOpen Cluster data base and the available literature, we re-examined theoverall properties of a sample of 30 clusters located towards theGalactic anticentre with the distances, ages and metallicitiesavailable. This cluster sample presents no evidence of an abundancegradient perpendicular to the Galactic plane, nor is an age-metallicityrelation found. However, a radial abundance gradient of -0.093 dexkpc-1 is derived over a Galactocentric distance of 14 kpc, agradient which is in keeping with most recent determinations. This valuepractically does not change when all clusters with basic parametersknown up to this date are considered.
| Morphology of Galactic Open Clusters
We analyzed the shapes of Galactic open clusters by the star-countingtechnique with the Two Micron All Sky Survey star catalog database.Morphological parameters such as the ellipticity and size have beenderived via stellar density distribution, weighed by clusteringprobability. We find that most star clusters are elongated, even for theyoungest star clusters of a few million years old, which are locatednear the Galactic disk. The shapes of young star clusters must reflectthe conditions in the parental molecular clouds and during the clusterformation process. As an open cluster ages, stellar dynamics cause theinner part of the cluster to circularize, but the overall radius getslarger and the stellar density becomes sparser. We discuss how theinternal relaxation process competes with Galactic external perturbationduring cluster evolution.
| On the recent star formation history of the Milky Way disk
We have derived the star formation history of the Milky Way disk overthe last 2 Gyr from the age distribution diagram of a large sample ofopen clusters comprising more than 580 objects. By interpreting the agedistribution diagram using numerical results from an extensive libraryof N-body calculations carried out during the last ten years, wereconstruct the recent star formation history of the Milky Way disk.Under the assumption that the disk has never been polluted by anyextragalactic stellar populations, our analysis suggests thatsuperimposed on a relatively small level of constant star formationactivity mainly in small-N star clusters, the star formation rate hasexperienced at least five episodes of enhanced star formation lastingabout 0.2 Gyr with production of larger clusters. This cyclic behaviourshows a period of 0.4+/-0.1 Gyr and could be the result of density wavesand/or interactions with satellite galaxies. On the other hand, the starformation rate history from a volume-limited sample of open clusters inthe solar neighbourhood appears to be consistent with the overall starformation history obtained from the entire sample. Pure continuous starformation both in the solar neighbourhood and the entire Galactic diskis strongly ruled out. Our results also indicate that, in the Milky Waydisk, about 90% of open clusters are born with N<=150 and the slopein the power-law frequency distribution of their masses is about -2.7when quiescent star formation takes place. If the above results arere-interpreted taking into consideration accretion events onto the MilkyWay, it is found that a fraction of the unusually high number of openclusters with ages older than 0.6 Gyr may have been formed in disruptedsatellites. Problems arising from the selection effects and the ageerrors in the open cluster sample used are discussed in detail.
| The age of the oldest Open Clusters
We determine ages of 71 old Open Clusters by a two-step method: we usemain-squence fitting to 10 selected clusters, in order to obtain theirdistances, and derive their ages from comparison with our own isochronesused before for Globular Clusters. We then calibrate the morphologicalage indicator δ(V), which can be obtained for all remainingclusters, in terms of age and metallicity. Particular care is taken toensure consistency in the whole procedure. The resulting Open Clusterages connect well to our previous Globular Cluster results. From theOpen Cluster sample, as well as from the combined sample, questionsregarding the formation process of Galactic components are addressed.The age of the oldest open clusters (NGC 6791 and Be 17) is of the orderof 10 Gyr. We determine a delay by 2.0±1.5 Gyr between the startof the halo and thin disk formation, whereas thin and thick disk startedto form approximately at the same time. We do not find any significantage-metallicity relationship for the open cluster sample. The cumulativeage distribution of the whole open cluster sample shows a moderatelysignificant (˜ 2σ level) departure from the predictions foran exponentially declining dissolution rate with timescale of 2.5 Gyr.The cumulative age distribution does not show any trend withgalactocentric distance, but the clusters with larger height to theGalactic plane have an excess of objects between 2-4 and 6 Gyr withrespect to their counterpart closer to the plane of the Galaxy.
| Intermediate-age Galactic open clusters: fundamental parameters of NGC 2627
Charge-coupled device (CCD) photometry in the Johnson V, Kron-Cousins Iand Washington CMT1 systems is presented in the field of thepoorly known open cluster NGC 2627. Four independent Washingtonabundance indices yield a mean cluster metallicity of [Fe/H]=-0.12 +/-0.08, which is compatible with the existence of a radial gradient in theGalactic disc. The resultant colour-magnitude diagrams indicate that thecluster is an intermediate-age object of 1.4 Gyr. Based on the best fitsof the Geneva group's isochrones to the (V, V-I) and (T1,C-T1) diagrams, we estimate E(V-I) = 0.25 +/- 0.05 andV-MV= 11.80 +/- 0.25 for logt= 9.15, and E(C-T1) =0.23 +/- 0.07 and T1-MT1= 11.85 +/-0.25 for logt= 9.10, respectively, assuming solar metal content. Thederived reddening value E(C-T1) implies E(B-V) = 0.12 +/-0.07 and a distance from the Sun of 2.0 +/- 0.4 kpc. Using the WEBDAdata base and the available literature, we re-examined the overallproperties of all the open clusters with ages between 0.6 and 2.5 Gyr.We identified peaks of cluster formation at 0.7-0.8, 1.0-1.1, 1.6-1.7and 2.0-2.1 Gyr, separated by relative quiescent epochs of ~0.2-0.3 Gyr.We also estimated a radial abundance gradient of -0.08 +/- 0.02, whichis consistent with the most recent determinations for the Galactic disc,but no clear evidence for a gradient perpendicular to the Galactic planeis found.
| Metallicity distribution on the galactic disk
Depending mainly on UBVCCD data, the metallicities of 91 open starclusters nearby the galactic disk have been estimated using Cameron's[A&A 147 (1985b) 39] method. The metallicity radial gradient alongthe galactic plane is found to be -0.09 dex/kpc; which is in a very goodagreement with Panagia and Tosi [A&A 96 (1981) 306] and Carraro etal. [MNRAS 296 (1998) 1045]. Vertically on the galactic disk, withinabout 800 pc, the metallicity gradient is found to be so trivial. Anaverage age-metallicity relation has been examined, which confirms theprevious suggestion that the metallicity of a cluster depending mainlyon its position on the galactic disk more than its age.
| On the Galactic Disk Metallicity Distribution from Open Clusters. I. New Catalogs and Abundance Gradient
We have compiled two new open cluster catalogs. In the first one, thereare 119 objects with ages, distances, and metallicities available, whilein the second one, 144 objects have both absolute proper motion andradial velocity data, of which 45 clusters also have metallicity dataavailable. Taking advantage of the large number of objects included inour sample, we present an iron radial gradient of about -0.063+/-0.008dex kpc-1 from the first sample, which is quite consistentwith the most recent determination of the oxygen gradient from nebulaeand young stars, about -0.07 dex kpc-1. By dividing clustersinto age groups, we show that the iron gradient was steeper in the past,which is consistent with the recent result from Galactic planetarynebulae data, and also consistent with inside-out galactic diskformation scenarios. Based on the cluster sample, we also discuss themetallicity distribution, cluster kinematics, and space distribution. Adisk age-metallicity relation could be implied by those properties,although we cannot give conclusive result from the age- metallicitydiagram based on the current sample. More observations are needed formetal-poor clusters. From the second catalog, we have calculated thevelocity components in cylindrical coordinates with respect to theGalactic standard of rest for 144 open clusters. The velocitydispersions of the older clusters are larger than those of youngclusters, but they are all much smaller than that of the Galactic thickdisk stars.
| Morphological analysis of open clusters' propertiesII. Relationships projected onto the galactic plane
A morphological analysis study of open clusters' properties has beenachieved for a sample of 160 UBVCCD open star clusters of approximately128,000 stars near the galactic plane. The data was obtained and reducedfrom using the same reduction procedures, which makes this catalogue thelargest homogeneous source of open clusters' parameters.
| Integrated photometric characteristics of galactic open star clusters
Integrated UBVRI photometric parameters of 140 galactic open clustershave been computed. Integrated I(V-R)0 and I(V-I)0colours as well as integrated parameters for 71 star clusters have beenobtained for the first time. These, in combination with published data,altogether 352 objects, are used to study the integrated photometriccharacteristics of the galactic open clusters. The I(MV)values range from -9.0 to -1.0 mag corresponding to a range in totalmass of the star clusters from ~ 25 to 4*E4 Msun.The integrated colours have a relatively narrow range, e.g., I(B-V){_0}varies from -0.4 to 1.2 mag. The scatter in integrated colours at agiven integrated magnitude can be understood in terms of differences infraction of red giants/supergiants in the clusters. The observedintegrated magnitudes and colours agree with the synthetic ones, exceptthe dependences of I(V-R)0 and I(V-I)0 colours forclusters younger than ~ 100 Myrs and also of the integrated magnitudesof oldest clusters. The large sample provides the most accurate agedependence of integrated magnitudes and colours determined so far. Theluminosity function of the I(MV) has a peak around -3.5 magand its slope indicates that only ~ 1% of the open clusters in thegalactic disc are brighter than I(MV)=-11 mag. No variationhas been found of integrated magnitude with galactocentric distance andmetallicity.
| Morphological analysis of open clusters' propertiesI. Properties' estimations
A sample of 160 UBVCCD observations of open star clusters near thegalactic plane has been studied, and a catalogue of their propertiesobtained. The main photometrical properties have been re-estimated selfconsistently and the results have been compared with those of Lynga[Lynga, G., 1987. Catalog of Open Cluster Data, 5th Edition, StellarData Centers, Observatoire de Strasbourg, France].
| Foreground and background dust in star cluster directions
This paper compares reddening values E(B-V) derived from the stellarcontent of 103 old open clusters and 147 globular clusters of the MilkyWay with those derived from DIRBE/IRAS 100 mu m dust emission in thesame directions. Star clusters at |b|> 20deg showcomparable reddening values between the two methods, in agreement withthe fact that most of them are located beyond the disk dust layer. Forvery low galactic latitude lines of sight, differences occur in thesense that DIRBE/IRAS reddening values can be substantially larger,suggesting effects due to the depth distribution of the dust. Thedifferences appear to arise from dust in the background of the clustersconsistent with a dust layer where important extinction occurs up todistances from the Plane of ~ 300 pc. For 3 % of the sample asignificant background dust contribution might be explained by higherdust clouds. We find evidence that the Milky Way dust lane and higherdust clouds are similar to those of several edge-on spiral galaxiesrecently studied in detail by means of CCD imaging.
| Fundamental properties of the open cluster NGC 2355
NGC 2355 is an old open cluster in the outer part of the galactic disk(l=203fdg4 , b=+11fdg8 ) which has been little studied until now. Thispaper presents the first astrometric and spectroscopic investigation ofthis cluster. We have measured precise absolute proper motions from oldCarte du Ciel plates, POSS-I plates and recent CCD observations obtainedwith the Bordeaux meridian circle. The proper motion data reveal 38highly probable cluster members down to Blim = 15 mag within7' of the cluster center. We have also obtained ELODIE high resolutionspectra for 24 stars. Seventeen of them are confirmed to be members ofthe cluster on the basis of radial velocity. Eight of them are fastrotating turnoff stars for which the projected rotational velocity hasbeen determined. The spectroscopic observations have also providedestimates of the physical parameters Teff, log g, {[Fe/H]},MV of the 24 target stars. Two stragglers have beenidentified in the cluster. Combining our astrometric and spectroscopicresults with previous UBV photometry and recent JHK_s photometry fromthe 2MASS survey we have derived the fundamental properties of thecluster: metallicity, age, distance, size, spatial velocity and orbit.Based on observations made on the 193cm telescope at the Haute-ProvenceObservatory, France, and on plate digitisation at the Centre d'Analysedes Images, Paris. This publication makes use of data products from theTwo Micron All Sky Survey, which is a joint project of the University ofMassachusetts and the Infrared Processing and Analysis Center, funded bythe National Aeronautics and Space Administration and the NationalScience Foundation.
| Remembering Gemini.
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| Catalogue of blue stragglers in open clusters.
An extensive survey of blue straggler candidates in galactic openclusters of both hemispheres is presented. The blue stragglers wereselected considering their positions in the cluster colour-magnitudediagrams.They were categorized according to the accuracy of thephotometric measurements and membership probabilities. An amount of 959blue straggler candidates in 390 open clusters of all ages wereidentified and classified. A set of basic data is given for everycluster and blue straggler. The information is arranged in the form of acatalogue. Blue stragglers are found in clusters of all ages. Thepercentage of clusters with blue stragglers generally grows with age andrichness of the clusters. The mean ratio of the number of bluestragglers to the number of cluster main sequence stars is approximatelyconstant up to a cluster age of about 10^8.6^ yr and rises for olderclusters. In general, the blue stragglers show a remarkable degree ofcentral concentration.
| The Old Open Clusters Of The Milky Way
The Galactic open clusters, in particular the oldest members, serve asexcellent probes of the structure and evolution of the Galactic disk.Individual clusters provide excellent tests of stellar and dynamicalevolution. Cluster spatial and age distributions provide insight intothe processes of cluster formation and destruction that have allowedsubstantial numbers of old open clusters to survive.Spectroscopic andphotometric data for the old clusters yield kinematic, abundance, andage information that clarifies the relationship between the old opencluster population and other Galactic populations. New samples of oldopen clusters, which span a large range in distance and age, are used todefine disk abundance gradients and the cluster age-metallicityrelationship, and they point to a complex history of chemical enrichmentand mixing in the disk.
| Physical parameters of the intermediate age open cluster IC 1311: Clues for the theory of stellar evolution
The results of a UBVR photometric study in the field of the open clusterIC 1311 are presented. A comparison with previously published results onNGC 7044, based on measurements secured during the same observing run,leads to a self-consistent constraints to the parameters of the cluster.The location of selected samples of giant and unevolved dwarf members inthe U-B vs B-V diagram is used to simultaneously compute the colorexcess E(B-V) and the metallicity (Fe/H). Distance modulus and age areestimated by the Zero Age Main Sequence (ZAMS) fitting method, and bythe use of theoretical isochrones, based on models computed with andwithout the consideration of convective overshooting during the phasesof core nuclear burning. The adopted set of values is: E(B-V) = 0.28,(Fe/H) = 0.0, DM = 13.9, Age = 1.6 x 109 yr. The massfunction for the cluster main sequence has been estimated, with a slopex = -2.58, significantly steeper than the Salpeter initial mass function(IMF) (-1.35). The uncertainties in the adopted values for the clusterparameters, due to interstellar reddening, and to the calibrations oftheoretical luminosity and effective temperature in terms ofobservational quantities, are also addressed. The discrepancies betweenthe observational color-magnitude (CM) and the model isochrones, inparticular the difference between observed and predicted luminosity ofthe red giant clump (RGC), are sensibly reduced for the models withconvective core overshooting. The results indeed suggest the need ofincreasing the overshooting effectiveness beyond the values consideredup to now in evolutionary computations.
| The galactic system of old star clusters: The development of the galactic disk
The vast majority of open clusters persist as clusters for no more thana few hundred million years, but the few which survive for much longerperiods constitute a unique sample for probing the evolution of thegalactic disk. In a charge coupled device (CCD) photometric survey forpossible old open clusters combined with previously publishedphotometry, we have developed a list of 72 clusters of the age of theHyades or older (Phelps (1994). Using our version of parameters based onthe luminosity difference between the main sequence turnoff and thehorizontal branch and on the color difference between the turnoff andthe giant branch, we have calculated a 'Morphological Age Index' (MAI)for the clusters in our list and for a sample of globular clusters. Wefind that the MAI is well correlated with the logarithm of cluster ages,as determined by fitting to theoretical isochrones. We conclude that theindex is a good measure of the relative ages of both globular and openclusters, although uncertainties in the models and residual metallicityeffects prevent the use of the MAI as a definitive calibration of actualcluster ages. The age distribution of the open clusters overlaps that ofthe globular clusters, indicating that the galactic disk began todevelop toward the end of the period of star formation in the galactichalo. The open cluster age distribution can be fit approximately with atwo-component exponential decay function; one component can beidentified as the tail of the dominant population of thin disk openclusters with an age scale factor of 200 Myr, and the other consists oflonger-lived clusters with an age scale of 4 Gyr. The young openclusters are distributed on the galactic plane almost symmetricallyabout the Sun with a scale height perpendicular to the galactic plane of55 pc. The old population consists of rich clusters found only in theouter disk, nore than RGC = 7.5 kpc from the galactic center;this population has a scale height of 375 pc. After accounting for thetwo exponential distributions of cluster ages, there are indications ofan excess of clusters in the age range of 5-7 Gyr; there may have beenlarge bursts of star formation in that period, or perhaps a largerproportion of the clusters forming at that time had advantageous orbitsfor survival. Either circumstance is consistent with the idea that thegalactic disk has been repeatedly disturbed, possibly in collisions orother interactions with external systems, resulting in the occasionalformation of clusters with relatively large velocities perpendicular tothe plane; these are the clusters that have survived until the present.Finally, the repeated accretion of low angular momentum material ontothe disk from the halo or beyond would also explain the observed radialcomposition gradient and the lack of a correlation between open clustermetallicity and age found by Friel & Janes (1993).
| CCD photometry of distant open clusters. I. Berkeley 22, Berkeley 29 and Berkeley 54.
We present deep BVI photometry for three previously unstudied rich anddistant open clusters. The color-magnitude diagrams of all studiedobjects show well-defined main-sequences and clumps of helium burninggiants. Estimates of age, reddening and distance are given for alltarget clusters. Ages of Be 54 and Be 29 are close to the age of M 67(about 4Gyr on the scale of Geneva isochrones). Age of Be 22 is about3Gyr. Heliocentric distance of Be 29 is estimated at 10.5 kpc while itsgalactocentric distance is about 19kpc. Be 29 seems to be the mostdistant galactic open cluster known in sense of its heliocentric as wellas galactocentric distance. A clearly marked sequence of binaries isvisible on the color-magnitude diagram of Be 29. Two likely candidatesfor evolved giants belonging to the very extended halo of Be 29 wereidentified. Our photometry suggests extremely low metallicity of Be 29.Several candidates for variable stars were found in the field of Be 54.
| Development of the Galactic disk: A search for the oldest open clusters
In an extensive charge coupled devices (CCD) photometric survey ofpotential old open clusters, we have identified a number of systems thatare indeed old; some of them are among the oldest of the open clusters.Using our versions of two well-known morphological age indices, onebased on the luminosity difference between the main sequence turnoff andthe horizontal branch and the other on the color difference between theturnoff and the giant branch, we have ranked the open clusters inapproximate order of age. Our data together with previously publishedphotometry of other old open clusters, yields a catalogue of 72 clustersof the age of Hyades or older with 19 of the clusters as old or olderthan M67 (about 5 Gyr). Among the oldest open clusters are Be 17, Cr261, NGC 6791, Be 54, and AM 2. Be 17 and another old cluster, Lynga 7,are possibly as old as the youngest globulars. The data also suggestthat the formation rate of open clusters may have been higher early inthe history of the disk than at intermediate times since numerousclusters have survived from that time.
| New dating of galactic open clusters
A new set of isochrones for solar metallicity computed from modelstaking into account mass loss and moderate overshooting and using therecent opacity tables by Rogers and Iglesias (1992) has been used todetermine the ages of 30 galactic open clusters covering an interval ofage from 4 million to 9.5 billion years. The clusters collected hereconstitute an ensemble of homogeneous and accurate data, well discussedfor distance, reddening, membership and binarity, and thus they providea basic reference for age determinations. The present set of isochronesfits the observed color-magnitude diagrams of the clusters veryaccurately, and may thus be expected to provide reliable ages. Analyticrelations between several characteristics of the isochrones and the ageare given and can be used for further age calibrations consistent withthis homogeneous scale.
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| Open clusters as standard candles - The age-metallicity relation and metallicity gradients
An overview is presented of a series of investigations of the use of theopen clusters as probes of the history of the galactic disk. Noindications are found of a gradient in metallicity perpendicular to thegalactic plane; along the plane, there is a very definite radialgradient. There is also no evidence for a systematic trend inmetallicity with cluster age, and it appears that the metallicity of adisk star depends entirely on its place of formation. On the basis ofthe spectra considered, it is possible to derive a metallicity that isprimarily based on Fe lines and another based on the Mg b + Mg IIfeature.
| Preliminary CCD Photometry of the Open Cluster NGC 2355
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| The Praesepe-age anticenter cluster NGC 2355
CCD photometry on the UBV system is presented for the central part ofNGC 2355, so far unstudied open cluster located in the galacticanticenter. The color-magnitude diagram (CMD) reveals a main sequenceand red giant clump. The foreground reddening is estimated to be E(B -V) = 0.12. The cluster age and metallicity are close to age andmetallicity of Praesepe. For the assumed (Fe/H) = 0.13 the apparentdistance modulus of NGC 2355 is 12.1 which corresponds to a positionabout 2.2 kpc near the direction of the galactic anticenter, and 440 pcabove the galactic plane. Eleven candidates for the cluster giants wereidentified. Examination of the CMD for the comparison field, located 19arcmin from the cluster center, suggest that majority of thesecandidates are cluster members. Red giants belonging to NGC 2355 showatypically large spread of colors as compared with populations of giantsobserved in other clusters with similar ages.
| King 8 - A metal-poor disk cluster
The faint cluster, King 8 (IAU designation C00546+336), was observed aspart of a study of galactic anticenter stars, which are used as probesof the environmental conditions in the outer galactic disk. Thedistribution of stellar ages and metallicities as a function of positioncan be compared to the properties of solar neighborhood stars, andthereby serve as constraints for theoretical models. BV observations areconsidered, taking into account photoelectric data, photographic data,and video camera data. The final photographic values for all starsmeasured are listed in a table. Video camera magnitudes were averagedwith photographic magnitudes when available. Attention is given to acolor-magnitude diagram, the luminosity function, a two-color diagram,slitless spectra, and IIDS spectrophotometry. The color-magnitudediagram morphology of King 8 suggests this open cluster is a moderateage, 800 million years, metal-poor (Y = 0.30, Z = 0.01) object locatedin the anticenter 3-4 kpc from the sun.
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