I posted a question on a physics forum about IMU alignment and using a star finder.
http://www.thenakedscientists.com/forum/index.php?topic=46824.new#new
The response was interesting:
"About that same time, I was trained to repair astrotrackers for USAF.
...
The astrotrackers I worked on were heavy and bulky. NASA must have had a less massive version.
Irrelevant, Apollo did not use automatic astrotrackers due to size, weight, and power considerations, when the pilot(s) could do the necessary alignment checks and adjustments with far simpler equipment.
A typical system back then, such as used in the Hound Dog missile, would include a gyro about 2 feet across, and astrotracker optical assembly maybe 18" across, and a computer of similar size to handle it.
The Apollo IMU was basically a gyro one foot across. A main part of the reduction was leaving out the fourth gimbal, and associated sensors and driver motors, used in most such system (including Gemini). Although dropping the gimbal could lead to gimbal-lock (check out
"a fourth gimbal for Christmas" at ALSJ), this could be avoided by some procedural changes, and the savings were considered well worth it.
"Also, I think NASA must have dropped some navigation aids on the lunar surface before they attempted any manned landings."
And he is as wrong as you, though it's possible he was simply [mis]led to that conclusion by all the blatant question begging in your query. Elevation was completely irrelevant, and as long as they were within maybe 100 miles of the planned landing site and could tell their orientation (such as the sun being in the east), they could make a suitable orbit to
begin rendezvous. Any precision beyond that, in terms of location, alignment, or relative position of the CSM, merely allowed for a better rendezvous. Of course they would want the best data they could get, to save time and fuel, and, yes, for pride in a job well done, but also for improved safety margins in case any problems occurred.
You still cling to this absurd notion that extreme precision was needed for the ascent module to make a single shot to "hit" the CSM in orbit or something. The reality is that's more like something you've probably seen in movies dozens of times -- someone jumping from one vehicle to another on the highway. In this case, all they had to do at the start was get onto a [very wide] highway going in the right direction; once that was done, either vehicle (or both) could adjust their speed or lane until they got together.