This point is called the First Point of aries.
"Lectures in Navigation"
Ernest Gallaudet Draper
Add to that the sun's R.A. or the distance in time the sun is from the First Point of aries at Greenwich Mean Noon.
"Lectures in Navigation"
Ernest Gallaudet Draper
You remember that, roughly speaking, the Sun's Right Ascension was the distance in time the sun was from the First Point of aries.
"Lectures in Navigation"
Ernest Gallaudet Draper