From Sweden to Spain: Aitoff and Hammer

[quadibloc]

In the Lund Observatory in Sweden, there is a magnificent painting and map of the starry heavens, in galactic coordinates, which took five years to make. That is, the map is also a painting.
It was completed in 1955. The web site of the observatory notes, no doubt correctly, that in 1950, Professor Knut Lundmark directed that this panorama of the Milky Way be produced on the Aitoff projection.
What it fails to note was that the panorama, which may easily be verified with a ruler, was actually painted in what most everyone who had an awareness of map projections thought the Aitoff projection was in 1950, and not the actual Aitoff projection. It was painted in the Hammer projection.
I've contacted the Lund Observatory webmaster about this, and I've also tried to contact a professor in Spain who contrasted a digital map derived from Gaia data on the Hammer projection with the Lund painting on the Aitoff projection in a blog post as well.
I hope my efforts will bear fruit.

[daan]

Good luck!

— daan

[Milo]

The Hammer projection is also known as the Hammer-Aitoff projection, as Hammer explicitly cited Aitoff as an inspiration for it. It's possible that someone saw "Hammer-Aitoff" and tried to abbreviate it to the wrong half.

[quadibloc]

The Hammer projection is also known as the Hammer-Aitoff projection, as Hammer explicitly cited Aitoff as an inspiration for it. It's possible that someone saw "Hammer-Aitoff" and tried to abbreviate it to the wrong half.

Well, that may have happened on occasion.
But this isn't an isolated incident; it's a long story.
Today, this projection is called the Hammer projection, or the Hammer-Aitoff projection.
I refer you to https://www.jstor.org/stable/212233 and https://adsabs.harvard.edu/full/1993Obs...113..213J.
From Leighly's paper, we learn that in 1912, Arthur R. Hinks referred to the Hammer projection simply as the "Aitoff Equal-Area Projection". The actual Aitoff projection was sufficiently obscure that it was often just called the Aitoff projection. It wasn't until 1952, as noted in my second reference, a letter of M. H. Jones to The Observatory, that H. J. Andrews called the attention of the English-speaking cartographic world to the error.