The unaided eye part III

Abstract

Coincidence observations; description of apparatus and safeguards. Coincidence accuracy observations with results. Variables that affect the observations. Distinction between precision and adjustment errors. Variation of precision with length of thick coincidence lines, similar results for thin lines. Minimum precision error relatively to length of coincidence line. Effect on precision of separating line thickness. Adjustment errors. Effect on adjustment of separating line thickness. Variation with length of line. Variation with thickness of line. Effect of premature judgment. Verticalising power of eye. Relation to coincidence adjustment error. Effect of astigmatism on error.