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How about this for an idea?  A line through Merak and Dubhe points roughly north, so we must be looking roughly north.  The Celestial Sphere looks like a disk rotating around the North Celestial Pole (NCP), so if we can find a star just scraping the horizon and we know its declination our latitude is 90-dec star (or something like that).  Alternatively, dec Talitha is 48*, so Talitha is 42* below Polaris.  If we can measure the height of Talitha above the horizon and add 42, we have our latitude. 
Dec Talitha = 48.04* so Talitha is 41.56* below the NCP.
Dec Dubhe = 61.75*
Dec Merak =  56.38*
Difference =  5.37* for scaling
On my screen Dubhe to Merak = 36mm, Talitha to the horizon = 110mm
Height Talitha = 110/36 x 5.37 = 16.41*
Therefore, our lat is 41.56* + 16.41* = 57.97*, which is on the Lewis Harris Border.
However it’s less than one degree below Callanish (58.2N) where the ground is littered with sets of stones.  The light is possibly Aird Laimishadar Light 1Fl W 6, which is described as a “flatpack lighthouse” and nothing like the noble 1862 Butt of Lewis Lighthouse a bit further north-east.  Usual caveat, I might be completely wrong.  DaveP