NavList:

Bill Lionheart
You talked of estimating the position of the horizon at night from a photograph.

Just to try and turn this into layman’s terms, are you saying that on a clear night you might be able to see the stars but be unable, for whatever reason, to work out where the horizon is, so you can’t use the stars to obtain position lines using a marine sextant?

Therefore, take a photograph which includes the brightest recognizable stars and use this Hough technique to predict where the horizon might be on the photograph.  Then use a pixel count to find the Hs of a required star and thus a position line.

An alternative approach might be to take a vertical photograph and use the same technique to predict your zenith at the instant the photograph was taken.  Then use pixel counts to measure zenith distances of all the brightest stars in the photograph.  Use these statistically to make a best guess of your position***.  DaveP

*** ”How to bluff your way in Mathematics” by A Bloke I Know.