No description of Piazzi Smyth’s researches would be complete without mention of the Apex of the Sun’s motion – i.e. the point in the sky towards which the Sun is moving.
He made this project a reality as early as 1847. It relies on a knowledge of the Proper Motions of the stars and so significant passage of time is a requirement in order to establish such proper motions.
Piazzi Smyth stated at the outset that he would track the proper motions of up to 2000 stars over a 30 year period in order to achieve his aim. An aim that ultimately led to 16 years examining and correlating what turned out to be almost 4,000 stars and he published this work in two parts.
In the image above we see, on the left, a typical publication of the work carried out in the observatory by both Henderson and Piazzi Smyth. On the right we see the publication of the 16 years of effort that went into his “proper motion” stellar atlas – almost certainly the first such atlas in existence.
Sadly, despite the monumental effort in creating these two volumes it did not translate into the solution for the Apex of the Sun’s motion. But he was close for the problem was solved within 5 years of his death, and it has been further refined over the years.
Piazzi Smyth called it a day after publishing these two volumes. He resigned from his position as Astronomer Royal for Scotland, and went into retirement in Ripon where he spent 12 years studying Meteorology and engaging in further Spectroscopic work.
Dr Bruce Vickery