The butterfly diagram in the 18th century

Digitized images of the drawings by J.C. Staudacher were used to determine sunspot positions for the period of 1749-1796. From the entire set of drawings, 6285 sunspot positions were obtained for a total of 999 days. Various methods have been applied to find the orientation of the solar disk which is not given for the vast majority of the drawings by Staudacher. Heliographic latitudes and longitudes in the Carrington rotation frame were determined. The resulting butterfly diagram shows a highly populated equator during the first two cycles (Cycles 0 and 1 in the usual counting since 1749). An intermediate period is Cycle 2, whereas Cycles 3 and 4 show a typical butterfly shape. A tentative explanation may be the transient dominance of a quadrupolar magnetic field during the first two cycles.Comment: Accepted for publication in Solar Physics, 1 table, 2 figure

The Effects of Atmospheric Dispersion on High-Resolution Solar Spectroscopy

We investigate the effects of atmospheric dispersion on observations of the Sun at the ever-higher spatial resolutions afforded by increased apertures and improved techniques. The problems induced by atmospheric refraction are particularly significant for solar physics because the Sun is often best observed at low elevations, and the effect of the image displacement is not merely a loss of efficiency, but the mixing of information originating from different points on the solar surface. We calculate the magnitude of the atmospheric dispersion for the Sun during the year and examine the problems produced by this dispersion in both spectrographic and filter observations. We describe an observing technique for scanning spectrograph observations that minimizes the effects of the atmospheric dispersion while maintaining a regular scanning geometry. Such an approach could be useful for the new class of high-resolution solar spectrographs, such as SPINOR, POLIS, TRIPPEL, and ViSP

Fundamentals of Astrometry

2004 text detailing the fundamentals of astrometry at milli- and micro-arcsecond accuracies

The g305 star-forming complex: Embedded massive star formation discovered by herschel hi-gal

We present a Herschel far-infrared study towards the rich massive star-forming complex G305, utilizing PACS 70, 160 ?m and SPIRE 250, 350, and 500 ?m observations from the Hi-GAL survey of the Galactic plane. The focus of this study is to identify the embedded massive star-forming population within G305, by combining far-infrared data with radio continuum, H2O maser, methanol maser, MIPS and Red MSX Source survey data available from previous studies. By applying a frequentist technique we are able to identify a sample of the most likely associations within our multiwavelength data set, which can then be identified from the derived properties obtained from fitted spectral energy distributions (SEDs). By SED modelling using both a simple modified blackbody and fitting to a comprehensive grid of model SEDs, some 16 candidate associations are identified as embedded massive star-forming regions. We derive a two-selection colour criterion from this sample of log (F70/F500)=1 and log (F160/F350)=1.6 to identify an additional 31 embedded massive star candidates with no associated star formation tracers. Using this result we can build a picture of the presentday star formation of the complex, and by extrapolating an initial mass function, suggest a current population of 2×104 young stellar objects (YSOs) present, corresponding to a star formation rate (SFR) of 0.01-0.02M yr-1. Comparing this resolved SFR, to extragalactic SFR tracers (based on the Kennicutt-Schmidt relation), we find that the star formation activity is underestimated by a factor of?2 in comparison to the SFR derived from the YSO population. © 2012 The Authors