The StarScan plate measuring machine: overview and calibrations

The StarScan machine at the U.S. Naval Observatory (USNO) completed measuring photographic astrograph plates to allow determination of proper motions for the USNO CCD Astrograph Catalog (UCAC) program. All applicable 1940 AGK2 plates, about 2200 Hamburg Zone Astrograph plates, 900 Black Birch (USNO Twin Astrograph) plates, and 300 Lick Astrograph plates have been measured. StarScan comprises of a CCD camera, telecentric lens, air-bearing granite table, stepper motor screws, and Heidenhain scales to operate in a step-stare mode. The repeatability of StarScan measures is about 0.2 micrometer. The CCD mapping as well as the global table coordinate system has been calibrated using a special dot calibration plate and the overall accuracy of StarScan x,y data is derived to be 0.5 micrometer. Application to real photographic plate data shows that position information of at least 0.65 micrometer accuracy can be extracted from course grain 103a-type emulsion astrometric plates. Transformations between "direct" and "reverse" measures of fine grain emulsion plate measures are obtained on the 0.3 micrometer level per well exposed stellar image and coordinate, which is at the limit of the StarScan machine.Comment: 24 pages, 8 figures, accepted for PAS

Der diskrete Charme der Bourgeoisie - Ein Beitrag zur Soziologie des modernen Wirtschaftsbürgertums

Entgegen der These der Auflösungserscheinungen des Bürgertums stellt der Autor die Annahme auf den Prüfstand, dass wir es nach wie vor mit gesellschaftlichen Fraktionierungen bürgerlicher Lebensweisen zu tun haben. Am Beispiel autobiographischer Schriften von deutschen Topmanagern stellt der Text ein modernes Verständnis des Wirtschaftsbürgertums vor, das organisational (durch die Karrieremechanismen der Organisation) und institutionell (im Feld der Wirtschaft) verankert ist. Die moderne Sozialformation des Wirtschaftsbürgertums ist nur noch auf der Grundlage von Organisationen denkbar. Sie lässt sich, jenseits von Klasse und Stand, als Positionselite beschreiben. Anhand der Autobiographien lässt sich die Reproduktion dieser Elite auf Basis einer engen Verknüpfung zwischen familialer Herkunft, an organisationale Karrieren gebundene Leistungsbereitschaft und hoher formaler Bildung nachzeichnen. Die Abgrenzung in der Statusreproduktion zwischen Bildungs- und Wirtschaftsbürgertum weist der Autor am jeweiligen Verhältnis zur Bildung nach; zwar können beide einen hohen Bildungsgrad in Form von Bildungspatenten nachweisen, doch im Falle des Wirtschaftsbürgertums herrscht ein instrumentelles Verhältnis zur Bildung vor. Der hohe Bildungsgrad folgt hier dem Bedürfnis, den Status mittels formaler Bildung abzusichern und damit die Gefahr der eigenen Austauschbarkeit - als Personal der Organisation - zu kompensieren. Der Text macht außerdem generationale Effekte sichtbar; insbesondere indem er darlegt, inwieweit der "moderne Manager" einerseits in der Betonung seines Status seinen Vorgängern gleicht und sich doch gleichzeitig in der Art der Unternehmensführung abgrenzt - indem er bspw. die Managementkonzepte seiner Zeit aufgreift

Positive Interactions between Desert Granivores: Localized Facilitation of Harvester Ants by Kangaroo Rats

Facilitation, when one species enhances the environment or performance of another species, can be highly localized in space. While facilitation in plant communities has been intensely studied, the role of facilitation in shaping animal communities is less well understood. In the Chihuahuan Desert, both kangaroo rats and harvester ants depend on the abundant seeds of annual plants. Kangaroo rats, however, are hypothesized to facilitate harvester ants through soil disturbance and selective seed predation rather than competing with them. I used a spatially explicit approach to examine whether a positive or negative interaction exists between banner-tailed kangaroo rat (Dipodomys spectabilis) mounds and rough harvester ant (Pogonomyrmex rugosus) colonies. The presence of a scale-dependent interaction between mounds and colonies was tested by comparing fitted spatial point process models with and without interspecific effects. Also, the effect of proximity to a mound on colony mortality and spatial patterns of surviving colonies was examined. The spatial pattern of kangaroo rat mounds and harvester ant colonies was consistent with a positive interspecific interaction at small scales (<10 m). Mortality risk of vulnerable, recently founded harvester ant colonies was lower when located close to a kangaroo rat mound and proximity to a mound partly predicted the spatial pattern of surviving colonies. My findings support localized facilitation of harvester ants by kangaroo rats, likely mediated through ecosystem engineering and foraging effects on plant cover and composition. The scale-dependent effect of kangaroo rats on abiotic and biotic factors appears to result in greater founding and survivorship of young colonies near mounds. These results suggest that soil disturbance and foraging by rodents can have subtle impacts on the distribution and demography of other species

New methods of forming and aligning the instrumental frames of absolute transit circle catalogs

A new method of defining the declination axis of the instrumental frame of an absolute transit circle catalog has been developed utilizing observations from stars over the entire sky rather than, as in the past, observations of just circumpolar stars. This method allows the planetary observations to be used directly to align the axes of the instrumental frame thus constructed with DE200. The alignment process has been simplified and recast so that it does not feed back into the definition of the instrumental frame. A declination offset, which is unique to absolute transit circle observational catalogs, is discussed emphasizing the problem of its cross-correlation with rotation terms from the alignment process. When compared to "traditional" methods, these new procedures give similar results for those quantities in common but they also produce additional adjustments that were not accounted for previously

The U.S. Naval Observatory pole-to-pole catalog: W2

Between the years 1985 and 1996 the U.S. Naval Observatory (USNO), using two transit circles, one located in Washington, DC (U.S.A.) and the other in Blenheim, New Zealand, conducted an ambitious program of absolute observations of positions of celestial objects completely covering both hemispheres. Over 737 000 individual observations were made, primarily of the International Reference Stars (IRS) and FK5 stars, as well as all the major planets (except Pluto) and thirteen minor planets. This included some 55 000 observations of day-time objects including the Sun, Mercury, Venus, and Mars. 
The original objective was to form a traditional, all-sky catalog of absolute star positions which could be firmly linked to the dynamical system. However, with the success of the Hipparcos project and the adoption of the ICRF as the celestial reference frame, the primary focus of the pole-to-pole program changed. The stellar positions have been differentially reduced to the system of Hipparcos and these were used to tie the planetary observations into the ICRF. Thus the program has resulted in a body of high quality observational data (average standard deviation of a mean position of about 75 mas) that will provide important input for the production of ICRF-based ephemerides. This is particularly true for the outer and minor planets.