The Greenwich Photo-heliographic Results (1874 – 1976): Initial Corrections to the Printed Publications
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A new sunspot and faculae digital dataset for the interval 1874 – 1955 has been prepared under the auspices of the NOAA National Geophysical Data Center (NGDC). This digital dataset contains measurements of the positions and areas of both sunspots and faculae published initially by the Royal Observatory, Greenwich, and subsequently by the Royal Greenwich Observatory (RGO), under the title Greenwich Photo-heliographic Results (GPR), 1874 – 1976. Quality control (QC) procedures based on logical consistency have been used to identify the more obvious errors in the RGO publications. Typical examples of identifiable errors are North versus South errors in specifying heliographic latitude, errors in specifying heliographic (Carrington) longitude, errors in the dates and times, errors in sunspot group numbers, arithmetic errors in the summation process, and the occasional omission of solar ephemerides. Although the number of errors in the RGO publications is remarkably small, an initial table of necessary corrections is provided for the interval 1874 – 1917. Moreover, as noted in the preceding companion papers, the existence of two independently prepared digital datasets, which both contain information on sunspot positions and areas, makes it possible to outline a preliminary strategy for the development of an even more accurate digital dataset. Further work is in progress to generate an extremely reliable sunspot digital dataset, based on the long programme of solar observations supported first by the Royal Observatory, Greenwich, and then by the Royal Greenwich Observatory.
KeywordsGreenwich photo-heliographic results Positions and areas of sunspots and faculae New digital dataset Quality control procedures Printed publications Typographic errors Initial corrections
The authors thank J.H. Allen, R.A. Harrison, A.J. Perkins, F.R. Stephenson and J.S. Warburton for much valuable advice, assistance and encouragement during the preparation of this paper. They also thank a referee for suggesting important improvements to the presentation of the paper. The image shown in Figure 1 is adapted from a contact print located at Cambridge University Library (Royal Observatory Solar Plate Contact Print MS.RGO.51/3838). The original solar plate was acquired at the Dehra Dun Observatory, Uttar Pradesh, India, on 03 February 1897. Figure 1 is reproduced by kind permission of the Syndics of Cambridge University Library.
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