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Message: <blockquote data-quote="Binastro" data-source="post: 3567963" data-attributes="member: 111403">Lee.We are both crackers. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile    :)" loading="lazy" data-shortname=":)" />Well, at least I am.If Leica are claiming fields at 1000m, they should do just that.Build a straight wall exactly 1000m away centrally from an observing platform.Scientific lasers measure the Moon's distance to 10cm, so 1000m can be known to 1/1000 mm. But 10mm is good enough, even 100mm.Or surveyor's equipment.Then measure off the markings on the wall.At 8 degree field I think the wall is actually 1,002.5m distant from the observer at the field edge.However, with a 20 degree field the wall is I think 1,015.5m distant at the field edge.I have a problem with these linear field measures.The real world is spherical. The horizon is round not straight.The Earth is not flat, except for the flat Earth society.For military use, I accept that reticles measuring linear sizes are useful.But I think in degrees for field sizes.I understand Wernher Von Braun was asked to believe that we actually live inside a spherical Earth.I doubt he actually believed that.P.S.How many metres at 1000 metres is equivalent to a 180 degree angular field?</blockquote>