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"The angle of incidence equals the angle of reflection."

Therefore, the angle, as measured at the reflecting surface of the 
artificial horizon, to your eye is the same as Ho. Simple trig then 
gives you the answer for "X."
X = 6'-2'' divided by tan Ho. For Ho = 30° then X = 10.6'; Ho= 45° then 
X= 6'-2''; for Ho = 60° then X= 3.5'.

Don' call your eye position "height of eye" as this term has a specific 
definition in relationship to celestial navigation and is used to 
calculate the "dip" correction when using the natural sea horizon and 
has no relevance to the use of an artificial horizon. Using these terms 
incorrectly may cause you confusion later in your celnav.

Since you are not using the natural sea horizon you do not make a 
correction for dip.

We have all had the same problem you are having as the field of view is 
usually quite limited looking at a bowl of water so use the largest 
diameter bowl you can. It doesn't need to be very deep. Being as close 
to the bowl as possible increases the field of view so sit on the ground 
close to the bowl.  Set up the bowl, sit with the bowl between you and 
the sun and then back up slowly until you see the sun's reflection. Try 
to use the image from the center of the bowl, avoid the edge as the 
miniscus will distort the surface of the liquid (I use mercury) and give 
you an error in your alitude reading. Lining up the bottom edge of the 
sun's image in the index mirror with the top edge of its inverted image 
in the liquid gives you a lower limb observation.

Using the reading from your sextant requires some corrections. First, 
take the reading and apply the correction for index error, you must do 
this as the first step. Then divide by two. Then make the corrections 
for refraction, semi-diameter and parallax (just use the correction 
table in the Nautical almanac) and you arrive at observed altitude, Ho. 
DO NOT apply a dip correction no mater how tall you are or how high you 
are above sea level.


gl

Andrew Corl wrote:
>
> All,
>
> A number of years ago I purchased a Davis Mark III Sextant and 
> artificial horizon. I live in a land locked area. On a few occassions 
> I have dug out the horizon filled it with either water, or vegetable 
> oil, or motor oil and attempted to take a sun sight. My sextant only 
> goes out to 120d so I have to work when the sun is less than 60d above 
> the horizon. After several minutes of walking around attempting to 
> find the sun I gave up and got back to my yard work. So now I going to 
> make another attempt to get this working. I have enclosed attached a 
> diagram showing the general configuration of what I am looking for. My 
> height of eye is 6'2". Is there a way to calculate what x should be on 
> the attached diagram? If so what would the formula be? Since I have a 
> three day weekend I should have a little bit of time to work on this 
> issue. I think once I work it out a couple of times I should be able 
> to just walk up and find the sun fairly easily.
>
> Thanks,
> Andrew
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