it is possible to deduce location of the earth on its orbit around the sun, and hence the time by star transits: https://en.wikipedia.org/wiki/Transit_instrume

it is possible to deduce location of the earth on its orbit around the sun, and hence the time by star transits: https://en.wikipedia.org/wiki/Transit_instrument https://en.wikipedia.org/wiki/Transit_instrument consider for example 2 very distant stars, and a closer star in the middle, and all of them in a plane perpendicular to the ecliptic. as the earth rotates, the closest star seems to move left/right with respect to the "vertical" defined by the more distant stars. from such a star transit you know the earth has just passed through the plane defined by these stars, and hence know the earth's position, hence the time. in the past catalogues for transits were optimized for human use, i.e. close to each other, ... but a modernized i.e. software solution should not need such proximity, and could make use of all the visible stars to make a more accurate assessment. I was kind of asking if there were any free open source software, it would be kind of neat to have an emergency laptop (with some optics) loaded with openstreetmap and astronomical positioning software, ...