More details here: Lumens vs Candelas (candle) vs Lux vs FootCandle vs Watts vs Irradiance vs Illuminance

Also see:

https://www.pixelsham.com/2020/08/01/solid-angle-measures/

The cone angle of the sun refers to the angular diameter of the sun as observed from Earth, which is related to the apparent size of the sun in the sky.

The angular diameter of the sun, or the cone angle of the sunlight as perceived from Earth, is approximately 0.53 degrees on average. This value can vary slightly due to the elliptical nature of Earth’s orbit around the sun, but it generally stays within a narrow range.

Here’s a more precise breakdown:

• • Average Angular Diameter: About 0.53 degrees (31 arcminutes)
  • Minimum Angular Diameter: Approximately 0.52 degrees (when Earth is at aphelion, the farthest point from the sun)
  • Maximum Angular Diameter: Approximately 0.54 degrees (when Earth is at perihelion, the closest point to the sun)

This angular diameter remains relatively constant throughout the day because the sun’s distance from Earth does not change significantly over a single day.

To summarize, the cone angle of the sun’s light, or its angular diameter, is typically around 0.53 degrees, regardless of the time of day.

https://en.wikipedia.org/wiki/Angular_diameter