Right Ascension and Declination to the Horizon

[Philosophaie]

Let's just say I was on a ship in the middle of the ocean. I am at a certain Longitude and Latitude with a Right Ascension (RA0) and Declination (DEC0) looking straight up into the heavens. If I look East how many degrees (RA and DEC) difference from my initial location to the horizon? Also in the other directions also.

 

[tiny-tim]

Hi Philosophaie!

Depends on height.

The difference in declination depends only on height.

The difference in right ascension depends on height and on declination.

Draw a sphere, stick a pin in it of height h, and draw a tangent. ​

 

[Philosophaie]

The h=0 at mean sea level. You would only have the radius of the Earth at the specified longitude and latitude. I just want the extents of the RA and DEC window at sea level just a rough estimate.

 

[tiny-tim]

At h = 0, the horizon is at distance 0.

 

[Philosophaie]

The Right Ascension of the horizon at h=0 is not zero. The distance will always take into consideration the radius of the Earth in its calculations plus h. The value is dependent upon the time of year and time of day in addition to the Longitude and Latitude.