A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2017 Sep 30, 10:59 -0700
Start with a telephoto 150 mm or larger vintage lens that is non-zooming and has the focus taped at infinite focus (adaptor needed to attach to DSLR camera). Field of view will be around 8°. This means CN is restricted to sunrise and sunset images and very low altitude Moon and planets. There is a learning curve to the best settings and lightroon 5 developing. A quick initial calibration can be done by imaging a 4° distant horizontal angle at infinite focus then compare to a metal sextant reading of the same horizontal angle. Work up the minutes of arc per pixel and then test on a filtered sunset capture with a visible natural horizon. Dip will need to be applied to the camera angle Hs to get a working Ho for sight reduction. Calibrating wider angle lens is much more difficult and will test the photogragher/navigator's patience. Lots in the archives on this.
From: Andrés Ruiz
Date: 2017 Sep 30, 12:09 +0200