How to explain the equation 'Altitude of a star at culmination = co-latitude + declination'? Altitude of a star at culmination = co-latitude + declination.
I understand that the co-latitude is equal to the altitude of the celestial equator (since it is 90 degrees away from the NCP). I also understand that declination is the height of a star above the celestial equator.
But I am just unsure why you can directly link altitude and declination at the exact point of culmination?
And why is a star reaching its highest point as it crosses the meridian?
thanks for any help.
Unless the observer is at a geographic pole, the celestial equator is not parallel to the horizon but crosses it at an angle equal to the observer's colatitude.
A star's path across the sky is parallel to the celestial equator, with maximum altitude midway between the eastern and western horizons, i.e. on the meridian.

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