I have spent the last 3 days doing this.
So far, I've found nothing. My method:
First, a graphic showing how I interpreted elements of the coded circle:
http://imgur.com/QOFg1Dk.jpg
Armed with calculated lengths for the east and south distances, I converted them to Lat,Lon:
1/2 Circumference of Merope 5c = 4643km / 180 degrees = 25.8 km per degree Lat (and Lon, only at equator).
Thus:
461.61km east = +17.851 degrees
512km south = -19.8453 degrees
So, now we must place these coordinates in relation to where GP (the geographic position of Merope 5) is located. Thanks to others on this thread, and some hunting in-game, I established that Merope 5 is at 90* overhead at Lat (+15.78 to -15.78), Lon -116.7334. Apparently, due to a slightly non-circular orbit, Merope 5 travels in a north-south line overhead during an orbit.
Since my math is easy at the equator, and since Merope 5's path crosses it, I center the GP of Merope 5 at 0,-116.7334.
This results in the EP falling at +19.845,-134.5884. Adding Merope 5's north-south variance to this position the EP falls on a north-south line of coordinates:
Lat (+4.065 to +35.625), Lon -134.5844
And when I go there along that line, and turn my ship to heading 318 (the measured Angle of Azimuth on the coded graphic image), sure enough there is Merope 5, about 50-60 degrees up. The alignment of Merope 5 at that point varies with the planet orbit, but it's clear the setup appears to be in the correct general idea.
I flew that entire line north to south, and never found anything.
And since there appears to be some "unexpected" behavior with the north/south Latitude values (heading toward 0 degrees results in negative Latitudes, rather than positive), I rotated the placement of the EP triangle by 180 degrees. This gave again a north-south EP position range of:
Lat (-4.065 to -35.625), Lon -98.8824
Now, when I turn my ship to heading 138 (opposite of the Azimuth Angle, since I've rotated the position by 180 degrees), there is Merope 5 again at 50-60 degrees up. So my position is diagonally opposite from the original.
Flew the entire north to south line there, upside down at 1 to 2km altitude, and saw nothing.
Granted, there is huge room for error here. Small math errors could mean kilometers of course change. And my use of plane geometry on a spherical surface is probably not ideal.
But I had to get close, just to see if this was actually a Position Circle. This was the best I managed after 3 days. Maybe someone else can take it further!