Comet Finlay is a periodic comet in the solar system discovered by William Henry Finlay (Royal Observatory, Cape of Good Hope, South Africa) on September 26, 1886. It came to perihelion (closest approach to the Sun) on December 27, 2014, at around apparent magnitude 10.
When the first parabolic orbit calculations were made in 1886, there was a similarity between this orbit and that of Francesco de Vico's lost periodic comet of 1844 (54P/de Vico-Swift-NEAT). Lewis Boss (Dudley Observatory, Schenectady, United States) noted large discrepancies between the orbits and after further observations concluded that de Vico's comet could not be the same as Finlay's.
The 1899 apparition was missed, in 1910 a close pass with Jupiter increased the orbital period, in 1919 the path was off predictions and a new comet discovered by Sasaki (Kyoto Observatory, Japan) on October 25, 1919, was discovered to be Finlay's.
The magnitude of the comet declined after 1926, and it was not until 1953 that it has been observed on every return.
During the 2015 perihelion passage the comet outburst on 16 December 2014 from magnitude 11 to magnitude 9 becoming bright enough to be seen in common binoculars with a 50 mm objective lens. On December 23, 2014, 15P and Mars were only 1/6 of a degree apart in the sky after sunset. But by December 23, 2014, the comet had dimmed considerably since the outburst. On 16 January 2015, the comet outburst to magnitude 8.
The comet currently has an Earth-MOID of 0.01 AU (1,500,000 km; 930,000 mi). On October 25, 2060, the comet will pass roughly 0.04 AU (6,000,000 km; 3,700,000 mi) from the Earth.