A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Michael Jones
Date: 2020 Mar 19, 21:26 -0700
HO-249 was designed for use in aircraft navigation, and the bubble sextants used only read to one or two minutes. Their fixes were accurate to around 5 miles, and didn't need to be more precise as they could see a long way at altitude. Once the aircraft got within 20 - 50 miles they could rely on radionavigation.
There was a thread here about significant digits that might help answer this also.