This longitude indicator show a zodiac signs horizontal line boundaries that identify the start of the sign marked in the corresponding horizontal line label in the Y axis, this simplify the analysis of a planet effect within specific zodiac sign.
Note: The Neptune longitude indicator is based on an ephemeris array that covers years 2010 to 2030, prior or after this years the data is not available, this daily ephemeris are based on UTC time so in order to align properly with the price bars times you should set UTC as your chart timezone.
In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.