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Hi Alan.
I toyed a couple of days ago with the simplest AH - a bowl of water on a
chair in my garden. I found that it worked best if I positioned myself so
the sun reflection in the water was clearly visible, then with a zeroed
sextant (and both sets of sun shades on!!!) aim the sextant directly at the
sun and bring it down slowly to the image in the water by lowering the
sextant gradually and at the same time pushing the index arm forward so as
to keep the real sun in view all the time until the reflected image from the
AH appears underneath it. You are right - the lateral alignment of the two
images is very sensitive sensitive. You can rock the sextant very gently
from side to side as you bring the sun down to resolve this.


-----Original Message-----
From: Alan S
Sent: Thursday, March 22, 2012 11:41 PM
To: zvidoron@btinternet.com
Subject: [NavList] more on artificia;l horizons ala davis and mirror type

Possibly it all revolves around the fact that I haven't had all that much
practice doing sun shots with artificial horizons Of course, it could be
something else, for instance the position of Mars or something like that,
however the following is what I've gotten the last couple of days.

Using a Davis AH, either sitting on the ground or set on a dining chair,
about 18" high (450mm for those of metric persuasion, I get reasonable
shots, without particular difficulty.

Using a mirror AH, a home made assembly, one that is likely on the crude
side, this assembly set on the ground and leveled, the thing doesn't seem
willing to work, I can find the "mirror" sun, though as for the sextant sun,
while I know it is there, I know not where. Placeing this assembly on the
previously mentioned dining chair, after leveling the unit, I'm able to get
sun shots, the mirror sun being pretty obvious, though the sextant sun is
less easily found and held, the problem being, as we used to describe
regarding long range rifle shooting, one of windage, that is left/right
positioning of the sextant sun with respect to the mirror sun. Finding the
sextant sun with my mirror AH seems trickier than with the Davis AH.

Such might be the slings and arrows that are part of being a "landlocked
navigator". Lest I forget, thanks to those who have tried to keep mre
straight on this business.

Alan
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