isogonal

[ ahy-sog-uh-nl ]

/ aɪˈsɒg ə nl /

equiangular; isogonic.

isogonal line.

Origin of isogonal

1855–60; < Greek isogṓn(ios) equiangular (see iso-, -gon) + -al¹

i·so·go·nal·i·ty

[ahy-soh-guh-nal-i-tee] /ˌaɪ soʊ gəˈnæl ɪ ti/, noun i·sog·o·nal·ly, adverb

The former part is clearly on the isogonal where the declination is 0, the latter on the isogonal where it is 180.

Encyclopaedia Britannica, 11th Edition, Volume 17, Slice 3 |Various