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We demonstrate the feasibility of determining magnitudes of stars on archival photographic plates using a commercially available scanner. We describe one photometric approach that could serve as a useful example for other studies. In particular, we measure and calibrate stellar magnitudes from a 1903 photographic plate from the Yerkes Observatory collection, and demonstrate that the overall precision from our methods is better than 0.10 mag. Notably, these measurements are dominated by intrinsic plate noise, rather than noise introduced through the scanning/digitization process. The low expense of this approach expands the scientific potential to study variable stars in the archives of observatory plate collections. We use the serendipitous discovery of a candidate transient at photographic magnitude $pg$ = 16.60 in the spiral galaxy NGC 7331 to illustrate our photometric methods. If this unknown source is a supernova, it would represent the fourth known supernova in NGC 7331., 12 pages, 11 figures, submitting to PASP; comments welcome

A total of 1095 magnitude estimates for the long‐period classical Cepheid GY Sge (P = 51 days), derived from the photographic plate collections of Harvard College Observatory, Sonneberg Observatory, and Sternberg Astronomical Institute, were combined with 48 new radial velocity measures obtained using the correlation spectrometer on the 1 m reflector of the Crimean Astrophysical Observatory. The data, in combination with published photometry (including observations from the All Sky Automated Survey 3) and radial velocity measurements, cover a time baseline spanning 116 years. The resulting O - C data display evolutionary changes in the period of GY Sge amounting to + 203 ± 27 s yr−1, a value in good agreement with theoretical predictions for a star in the third crossing of the instability strip. Large cyclical drifts with durations of ~23,000 days superposed on the parabolic evolutionary trend in the O - C data exhibit the positive signature of random fluctuations in pulsation period, of magnitude similar to what is found in other pulsating stars of similar period.

We present the absolute proper motion of Nova Velorum 1999=V382 Vel based on photographic plate material from the Yale/San Juan Southern Proper Motion program. The absolute motion, on the system of the International Celestial Reference System, is μαcos δ = -11.5 ± 2.3 and μδ = -1.7 ± 1.9 mas yr−1. This proper‐motion measure adds to the growing number of such measures for novae and will eventually allow the secular parallax for this class of objects to be determined.We also report the preoutburst B and V photometry of V382 Vel. In its quiescent state, the nova has mean values of V = 16.56 and B−V = 0.14. A brightening by 0.5 mag is noted in 1970 (JD 2,440,705.542).

A new CCD image of the supernova remnant RCW 103 was taken in 1995 to compare with a photographic plate taken in 1970. We calculated the proper-motion expansion of the outer edge and several filaments by comparing radial slices through each of the data sets. The mean expansion rate of the outer edge is 1\farcs 8~±~0\farcs 2 per 25 years, or about 1100 km sec-1. At this velocity the remnant is most likely around 2000 years old. In addition, it must have made the transition from the double-shock phase of evolution to the point-blast phase fairly recently for the initial energy of the supernova explosion to be within a reasonable rang.

The PDS microdensitormeter has a high positional repeatability but low coordinate systematic accuracy because of the errors of the PDS mechanism. To improve the PDS coordinate system, a method to determine and correct the errors of PDS coordinate system with a glass grid is developed and applied to the PDS of Purple Mountain Observatory (PMO). With the method, the coordinate systematic errors of the PDS at PMO are reduced from ± 5 microns to ± 1 micron. The results of an astrometric application confirmed the effect of the method.

We have just completed scanning glass copies of the blue and red plates in the original Palomar Observatory - National Geographic Sky Survey (POSS I) for the fields with b >/= |20 deg.|. All of the detected images are being cataloged with positions, shapes, magnitudes and colors. The stellar and non-stellar images are separated using a neural network approach. We estimate that there will be nearly a billion stellar objects and image data for several million galaxies in the finished database. The database, including the cataloged objects and the pixel data for the non-stellar images, will be available to the scientific community on-line via Internet. This paper is the first of a series describing the APS Catalog of the POSS I. In this first paper we describe the operation of the APS and the scanning procedures and parameters for the POSS I.

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.

Polynomial adjustments for the reduction of plates taken with the astrograph at the Observatorio de Campinas, Sao Paulo, Brazil, were investigated. A statistical analysis was performed on the vectorial residual maps derived from the reductions of 11 photographic plates. The results have shown the 2nd degree model to be inadequate for the reductions. A radial distortion effect in the 7 degree X 7 degree field was detected. The 5th degree radial distortion term was found to be not significant. The 2nd degree plus a term of radial distortion of the 3rd degree and the 3rd degree polynomial models give residuals of the order of 0".30, compatible with the errors of the catalogues used (Perth 70 and PPM South, preliminary version). However there are evidences that the last model gives slightly better results than the former.

The PDS/Monet measuring engine at the National Optical Astronomy Observatory was used to obtain photometry of nearly 10,000 stars on the NGS/POSS and 2000 stars on the ESO/SRC Survey glass plates. These measurements have been used to show that global transformation functions exist that allow calibration of stellar photometry from any blue or red plate to equivalent Johnson B and Cousins R photoelectric magnitudes. The four transformation functions appropriate for the POSS O and E and ESO/SRC J and R plates were characterized, and it was found that, within the measurement uncertainties, they vary from plate to plate only by photometric zero-point offsets. A method is described to correct for the zero-point shifts and to obtain calibrated B and R photometry of stellar sources to an average accuracy of 0.3-0.4 mag within the range R between values of 8 and 19.5 for red plates in both surveys, B between values of 9 and 20.5 on POSS blue plates, and B between values of 10 and 20.5 on ESO/SRC blue plates. This calibration procedure makes it possible to obtain rapid photometry of very large numbers of stellar sources.

merging galaxy system, were measured by digital analysis of a photographic plate (20 A bandwidth filter). Despite evidence for earlier starburst activity, the present H II luminosity function is very similar to that for the LMC, including a supergiant H II region of 0.76 the luminosity of 30 Dor. The measured H II regions of NGC 3239 have an Ha total luminosity of 1.3 X 1040^ ergs-1^.

Photographic plate-measuring and reduction techniques are described which have proven to be quite successful in producing good-quality photometric data for plates of less than optimum quality. Examples are given of typical results obtained using linear calibrations of I exp 2 data derived from null-meter-centered, seeing-adjusted, and background-adjusted iris measurements. The advantages of linear calibrations for iris data are discussed.

A new stellar photometer is described. Its main advantage is that it can be incorporated without modification into any system which provides video images of stars from a photographic plate. It is a completely electronic system and as such is completely transportable.

We have developed a break-finding algorithm that we apply to the determination of approximate redshifts of galaxies via the redshifted 4000 A break. The algorithm is particularly well suited to low-resolution data where spectral lines are not seen and most of the redshift information is contained within the spectral breaks. The algorithm is impersonal and well suited to the automated computer analysis of a large quantity of data. If used in conjunction with a technique to separate automatically stars from galaxies (such as in Edwards, Borra, and Hardy 1985), it can give, automatically, redshifts for early-type galaxies in the field observed. The redshifts so obtained have a precision sufficient to identify distant clusters of galaxies, obtain their redshifts, and establish membership in superclusters. We have tested the algorithm with various samples of objects. Photographic spectra for the galaxies of the cluster of galaxies Abell 2670 give the worst results (σ~3000 km sec-1^) while the application to photographic spectra of stars gives standard deviations of 2000 km sec-1^. On the other hand, our photographic spectra have low signal-to-noise ratios and uncertainties in the zero point of the wavelength scale which is obtained from the emulsion green cutoff. Better data obtained with photoelectric detectors and having better-calibrated zero points should give better results. This expectation is buttressed by the excellent performance of the algorithm with high-quality photoelectric spectra from Sharples, Ellis, and Gray (1988).

We have developed automated software to process slitless spectra. The software, described in a previous paper, automatically separates stars from extended objects and quasars from stars. This paper describes our quasar search techniques and discusses the results. We compare and calibrate the performance of the software with a plate taken in a region of SA 57 that has been extensively surveyed by others using a variety of techniques: our automated software performs very well. We find that an eye search of the same plate is less complete than the automated search: surveys that rely on eye searches suffer from incompleteness at least from a magnitude brighter than the plate limit. We show how the complete automated analysis of a plate and computer simulations are used to calibrate and understand the characteristics of our data.

The distance and structural properties of the remote anticenter globular cluster Palomar 2 are deduced from a preliminary analysis of a deep V photographic plate of the cluster. Its apparent distance modulus is estimated to be (n - M)V = 20.1 plus or minus 0.4 with a heavy foreground reddening E(B - V) = 1.27 plus or minus 0.07, and hence a galactocentric distance of 26 kpc. New star counts from the plate material are made to derive its tidal radius and central concentration parameters, and thus an approximate value for its perigalactic distance. Palomar 2 is much more compact than other clusters at similar distances, suggesting that it is now being seen near the outer end of a highly eccentric (e greater than 0.8) orbit.

The high quantum efficiency of CCD detectors makes it possible to study faint features in supernova remnants that are only barely detectable on the longest photographic exposures. The advantages of the CCD over the photographic plate is particularly striking in the near infrared where photographic emulsions are inefficient and where interstellar absorption is much reduced. The fine seeing in Hawaii allows study of much finer detail than was previously possible at other sites. Observations of the Crab nebula in subarcsecond seeing show that the H-alpha filaments in this object consist of chains of stellar or quasi-stellar knots with diameters less than about 1.0 arcsec (0.01 pc).

The relative position angles and separations are given for visual double stars, obtained from photographic plates taken at the Yerkes Observatory.

The imaging mode of a portable Fabry-Perot interferometer system is described. A focal reducer (f/8→ f/0.95) allows one to obtain filtergrams of extended sources and, when coupled to a red Fabry-Perot interferometer (600.0 nm to 700.0 nm), interferograms of galactic nebulae. The detector is a photographic plate. To reduce the digitized interferograms, a complete set of software has been developed for the density-intensity conversion, the correction of optical distortion, radial-velocity measurements from the interferograms, and the making of LSR velocity maps. The algorithms are explained and some results of our study of the H II region S142 illustrate our data-handling techniques.

Photoelectric photometiy has been employed in many attempts to discover optical counterparts for radio pulsars. The techniques generally involve a searchby means of some form of data manipulation-for a component of optical variability that is harmonically related to the radio pulsation. Although the general method has found spectacular success in the case of NP 0532 (Cocke, Disney, and Taylor 1969), it requires a reasonably accurate position for the radio pulsar for, otherwise, the photometer field aperture must be so large that the admitted sky light interferes to an undesirable extent with the sensitivity of the system to the sought-after signal. Thus, for a pulsar having only a poorly known position, direct photography may offer some advantages owing to the fact that the photographic plate is a panoramic device with the result that the interference contributed by the sky is limited approximately to the flux in a solid angle subtended by the actual recorded star image. To see that this is true, consider the photographic limiting magnitude for the Kitt Peak National Observatory 84-inch telescope

The fifteen years since the war have seen drastic changes in astronomical equipment and observing techniques. Photomultiplier receivers have replaced the photographic plate for perhaps one-fourth to one-third of the observing time of most large telescopes, and this use is still increasing. Image-intensifier tubes are just beginning to become available. When these are perfected they will almost certainly replace the direct recording of star light on a photographic plate for much of the remaining observing time. Most large telescopes in the past have required from 5 to 20 years for their design and construction and have then had effective lives of a half-century or more. This means that telescopes now planned or in the design stage will be used chiefly with photoelectric devices rather than with the direct-photography instrumentation typical of the last few decades. Any prediction of the properties of a device such as an image-intensifier tube that is still in the early development stage is very dangerous. However, if these telescopes now planned are to have maximum effectiveness, it behooves us to make the best guesses that we can as to these properties and as to the telescope design that will take full advantage of them. The important influence of the properties of a receiver on telescope design may be illustrated by the changes brought about by the last such shift, namely, from visual to photographic observation. Thus the retina of the eye has a very narrow wavelength sensitivity range, about 80% of its sensitivity falling in a 1000 Â range. Furthermore the small field of view of high resolution of the eye makes it possible to vary the magnification and the intensity of illumination of the image on the retina to any value needed

The initial results of a photometric investigation concerning suspected metal-rich globular star clusters are presented in the form of pseudo color-magnitude (CM) diagrams, i.e., graphical displays of the photographic plate measurements of apparent brightuess. A semiautomated iris-diaphragm photometer was used to make the measurements of the plates. The mean iris values from the visual plates are plotted along the ordinate of the pseudo-CM diagram. The differences between the mean iris values of the star images on the blue and visual plates are plotted along the abscissa. The globular star clusters reported upon here are: NGC 3201, NCC 5927, and NGC 6388. Judging from the shapes of their pseudo-CM diagrams, the first cluster is definitely not metal-rich, but the remaining two clusters are. Key words: globular clusters - color-magnitude diagrams

A good deal of water has passed under the bridge since the days when several famous positional astronomers thought of radial-velocity measurements as a species of witchcraft, and shook their heads seriously over the results. A few of you may even remember that one of them expressed his disapproval of the "soda lines," when they were shown to him in the laboratory, and would doubtless have extended his opinion to include H and K, had they been more readily visible. That those days are long since past, however, we could have no better evidence than that a well-known positional astronomer should in later life have turned to radialvelocity measurements, and spent some fifteen years upon them, finally becoming the expert in whose honor this symposium is being held. Dr. Ralph Wilson has sometimes referred to himself as a "mopper-upper" of the scientific debris which other people have left, and we all recognize that, in addition to being an observer of the first order, he shows uncanny skill and judgment in combining and discussing the results of many different investigators. Fortunately for me, my place on this program precedes his, and so I shall be able to count upon him to gather up the loose ends, and especially to bring up to date the history of a field of study which has been in progress at the Mount Wilson Observatory for the past forty years. At the outset it should be stated that in this brief discussion I have not included nebular spectroscopy with its unique and extraordinary phenomena. When Dr. Humason finds the H and K lines shifted to where the normal //s line belongs, nearly out of the range of sensitivity of the ordinary photographic plate, we cannot but feel that such results constitute a field of investigation of their own, to be studied and interpreted separately. I suppose actual work on the measurement of stellar radial velocities at Mount Wilson may be said to have begun in 1911, when the large spectrograph for use at the Cassegrain focus of the 60-inch reflector was completed. Before this time an auto-col