Sep 21 – 23, 2015
Royal Observatory of Belgium
Europe/Brussels timezone

2016 transit of Mercury and the solar diameter: new opportunities after the Venus transits

Sep 21, 2015, 3:30 PM
Meridian Room (Royal Observatory of Belgium)

Meridian Room

Royal Observatory of Belgium

Avenue Circulaire - 3 - Ringlaan 1180 Brussels
4-Space era data versus historical records


Dr Costantino Sigismondi (ICRA)


The use of the planetary transits to measure the solar diameter exploits the accurate timing of the ingress and the egress of Mercury or Venus on the solar disk at relative radial angular velocities of 0.05 arcsec per second of time. Our analysis of the transits of Venus 2012 (observed in Huairou, China) and 2004 (in Rome and Athens) overcomes the famous black drop effect and it is presented in view of the forthcoming transit of Mercury of May 9, 2016. In particular the accuracy of the planetary ephemerides and some technical observational tips are considered to apply this historical method by observing only the ingress of the 2016 transit, as it will be possible for the majority of the European sites. The educational and scientifical opportunities offered by these measurements are discussed.


  1. historical planetary transits and accuracy of planetary ephemerides

  2. planetary vs lunar ephemerides

  3. overcoming black drop in data analysis

  4. 2016 Mercury transit from Europe and Americas

  5. suggested requirements

  6. conclusions

Primary author

Dr Costantino Sigismondi (ICRA)

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