# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Zenith distance and Ho question.
From: Robert Goldberg
Date: 2020 Dec 19, 06:00 -0800

I'm a self taught celestial navigator so my instructor has questionable credentials. I thought I understood the concept of the relationship between Ho and ZD, but not I question myself. I do understand that they are 90 degree complements of each other. To give an example of a celestial objects on the Horizon. If the Ho is calculated at 0 degrees, this would mean that the ZD is 90 degrees.  My question in turn is, does that mean the GP of the celestial object is 90 degrees x 60nm/degree = 5400 miles away from me (ie. am I on a circle with a radius of 5400 nm)? I can envision this easily if the celestial object is on my same meridian or if I am on the equator taking a sun sight and it happens to be the equinox.  But at other times of the year and day and at northern and southern latitudes, does a Ho of zero imply that the GP of celestial object is 5400 nm away from me?  When I am using my sextant,  am I measuring distances along a great circle regardless of what my latitude or time of day it is? I hope this question makes sense and please keep your responses appropriate to my level of understanding. Thanks much.

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