Both apps allow calibration and capturing of altitude
readings. CamSextant associates a camera view with
Differently from marine sextants, which compensate
instrument shaking naturally by design, the phone
version must be hold pointing sharp to the object
and steady while capturing the altitude. Difficult
sometimes. Hold your breath. Tap gently.
It is also
hard to see faint stars ( a camera limitation
I guess ).
CamSextant app is as simple as can be. By default,
the camera view is zoomed in, to allow precise pointing.
The angle of view is smaller than the regular camera
Calibration is done by pointing the phone
to the sea horizon and carefully tapping the
This is the "zero" of your device. Instrumental
altitude reading is automatically corrected
after calibration. Use the X button to clear
the calibration, setting it back to 0.
Once calibrated, to read the altitude Hs,
point the device to the celestial object (a star,
planet, Sun or Moon) and tap [--Mark--]
( or tap anywhere on the camera view ).
You'll hear a click. The app did not take a picture
of the star. Instead it saves the local time
and instrumental altitude Hs, as shown. The camera image is frozen for a couple seconds, so you can inspect the quality of the altitude capture. Tap again to release.
can be used in landscape and portrait orientations.
note: Magnetic azimuth
indicator does not work on some older phones.
You don't need any adaptation to the phone
to use CamSextant app. A plain phone will do. But
I wanted to try something different. The original iphone camera has wide field angle. This
is not so good for a sextant viewfinder. Marine
sextant eyepieces are more like tele objectives.
The small field angle is important for precise pointing. To remedy that I bought one of
those little phone lenses. It is a 8X magnification
objective ( I'm not associated with the lens
manufacturer in any way). There are a many options
in the market. This is what I did: