Instead, the astronomers saw the same features during every second orbit and recorded them, but disregarded those seen in the meantime, when Mercury's other face was toward the Sun, because the orbital geometry meant that these observations were made under poor viewing conditions.
Derimod så astronomerne de samme træk i hvert andet omløb og optegnede dem, men så bort fra dem, der kunne ses i mellemtiden, mens Merkurs anden halvdel vendte mod Solen, fordi banegeometrien betyder at disse observationer blev gjort under dårlige observationsforhold.