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On 2015-04-27 11:36, Carly Butler wrote:
> I
> knew I should have an artificial horizon, but I actually thought  it
> wasn't that important (!) and that I could get an approximate location
> that wouldn't be so far off.

You don't need an artificial horizon to have fun with a marine sextant.
In fact, I think "fun" and "artificial horizon" are mutually exclusive!
Fiddling around with a bowl of fluid is not my cup of tea. Never tried a
mirror artificial horizon, but it doesn't seem attractive. If I wanted
to dink with a bubble and leveling screws, I'd use one of my theodolites.

With just the sextant you can be spontaneous. For instance, in the
middle of writing the first paragraph I noticed it was twilight. Grabbed
my Astra and went outside. No stars yet, but there was the gibbous Moon
high in the sky. I had to go to the fence and shoot toward my porch. I'm
not used to that direction, but took a hurried sloppy shot anyway,
estimating where the horizon ought to be.

According to a subsequent calculation, what I judged to be horizontal
was actually 3° above the horizon. Not too good, but not terrible
considering the conditions. When I'm shooting in a familiar direction
where I know some reference points, I can get within a degree.

With an AH at night, the darker the better. But when you have to
estimate the horizon, darkness in a mixed blessing. It helps star
visibility, but your horizon references are harder to see. You have to
compromise and shoot in twilight, just like a sailor.

One mistake I made tonight - forgot to remove the scope. With an
estimated horizon the reduced accuracy doesn't justify a scope. In fact,
removing the scope *increases* accuracy because it's so easy to shoot
with both eyes open and thereby get a better sense of horizontal. It's
also much less trouble to find the body.

In some cases the scope helps with star visibility. But for the Sun,
Moon, and planets, it just makes observing more difficult and less accurate.

Of course "less accurate" applies to all observations with an estimated
horizon. But I find the satisfaction of an accurate observation is
relative to the equipment and techniques in use.

   

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