Not a war, just a sextant question.

[killarney_sailor]

Originally Posted by Minnewaska

I may give it a try for giggles. Since my iPad has an internal gps, I have to admit to being suspicious of the app. I guess I would feel better if it was wrong, but then........

Get suspicious if your positions are too accurate or if the app suggested that the GPS feature is required for offshore use. I agree with someone else, sighting along the edge of the IPad is just not that accurate. You might get accuracy to one degree (if lucky) but that won't do much for a useful position.

[AdamLein]

Originally Posted by hellosailor

Anyone who has used Google Sky Map can tell you that using a smartphone for anything astronmical can be a rude surprise. Mine kept saying "West" when I was looking SOUTH.

It turns out that this is a common error, the magnetic sensors in the smartphones need to be regularly recalibrated (you make voodoo figure 8 passes with the phone) in order to get anything near reality with them.

I've had similar problems with Google Sky Map. In my case it had no idea what direction I was facing and would routinely put solar system objects in incorrect relative positions, as though it were plotting for the wrong date, but displaying the correct date. Another problem was that it kept forgetting where I said I was. These things seem to have been resolved now.

Anyway, a "sextant app" only uses the accelerometer, AFAIK. They do have sensitivity problems but surprisingly I've rarely seen the Hs that the app gives be terribly wrong.

[svzephyr44]

Put this in a page named "something.html" and open it with your web browser. It works with the Sight Reduction Tables for Marine Navigation downloadable for free from Maritime Safety Information Also you can get a bunch of useful calculators for free at the same site.
..............................................

Pub 229

This page allows calculation of the data in the Sight Reduction Tables for Marine Navigation (Pub. No. 229). The main purpose of this calculator is to facilitate the practice of celestial navigation at sea.  A secondary purpose is to provide the solutions of a spherical triangle of which two sides and the included angle are known and it is necessary to find the values of the third side and adjacent angle.

Latitude:	(degrees) Same name as declination (minutes) Contrary name as declination
Declination:	(degrees) (minutes)
Local Hour Angle (LHA):	(degrees) (minutes)

Altitude (Hc):	(degrees)
	(minutes)
Azimuth (Z):	(degrees)
	(minutes)

-->
.................................................. .....