15P/Finlay
Comet Finlay is a periodic comet with an orbital period of 6 years discovered by William Henry Finlay on September 26, 1886. The next perihelion passage is July 13, 2021 when the comet will have a solar elongation of 54 degrees at approximately apparent magnitude 10. It last came to perihelion on December 27, 2014, at around magnitude 10. Of the numbered periodic comets, the orbit of 15P/Finlay has one of the smallest minimum orbit intersection distances with the orbit of Earth. In October 2060 the comet will pass about 5 million km from Earth.
Description
When the first 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. Lewis Boss noted large discrepancies between the orbits and after further observations concluded that de Vico's comet could not be the same as Finlay's.During the 1906 apparition the comet brightened to magnitude 6. 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 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.