NavList:

Bob Bossert, you wrote:
"I did a run of Venus-Moon. My best was .18' and my average was .6' "

Ok, but could you please remind us what type of sextant you're using for your lunar sights?

You asked:
"And trying to understand the algorithm for Error in lunar, Equivalent Error in Longitude, and Position Error. I'm sure the last 2 are based on derived Longitude."

Nope. The equivalent error in longitude is pedagogic info for a beginning lunarian to get a handle on the relative importance of the errors in their work. That number is simply the error in the lunar converted to a typical longitude error at the standard rate of 12 seconds of time per 0.1' (tenth of a minute of arc) error in the lunar distance. And the equivalent error in position is that number reduced by cos(latitude) --since an error or, let's say, 20' of longitude at the equator corresponds to about 14 nautical miles error at 45° latitude or 10 nautical miles at 60° latitude.

Your final paragraph is very difficult to decipher. You wrote:
"I tried to calculate Longitude using the Law of Cosines formula. Substituting Ho for Hc, using the UTC derived from the LD to come up with different GHS, and using assumed Latitude from my DR (actually my GPS location). Doing the calculations, I get a much bigger difference in Longitude. Am I on the wrong path?"

You could be on the wrong path. You probably are on the wrong path... But your description here is nearly impossible to figure out. Describe what you're trying to do in more detail. In fact, it would be best if you can provide an example. Try to avoid acronyms and jargon, too. Just describe your process...

Frank Reed