A puzzle: why is the circle "chipped"? (tags: translate/rotate/ofCircle)

I am trying to understand what is happening to this circle, and not having much luck.

This is part of a sample that draws and runs an analog clock. I deleted all the code that does not affect the problem. What is left of the code is pasted below, and here is a link to the resulting picture: https://picasaweb.google.com/lh/photo/5svsM8HLJ5h3CXTgPFcJ8aSH89-kaxz6dMebCPTVqB0?feat=directlink

Needless to say, I am new to openFrameworks, and would appreciate any comments/suggestions.

Thanks in advance

#include "ofApp.h"

int sec;
int mymin;
int hour;



//--------------------------------------------------------------
void ofApp::setup(){
    
    //Make everything look nice and smooth.
    ofSetCircleResolution(100);
    ofEnableSmoothing();
    
    //Set size & position of our clock
    if( ofGetHeight() < ofGetWidth() )
        radius = (ofGetHeight()/2)-80;  //+++++++++
    else
        radius = (ofGetWidth()/2)-80;   //+++++++++
    
    top = (ofGetHeight()/2);
    myleft = (ofGetWidth()/2);

    ofBackground(0, 0, 0);

}

//--------------------------------------------------------------
void ofApp::update(){

}

//--------------------------------------------------------------
void ofApp::draw(){
    
   
    //Set the coortinate system to the center of the clock.
    ofPoint circle_center = ofPoint( myleft, top);
    ofTranslate(circle_center);
    ofRotateZ(-90);
    
 
    //Draw Outline of the clock
    ofSetLineWidth( (radius/100)*4 );
    ofNoFill();
    ofSetColor(0,79,223);
    ofCircle( ofPoint(0,0), radius );
    
    ofCircle( ofPoint(0,0), radius-40 );


}

#pragma once

#include "ofMain.h"

class ofApp : public ofBaseApp{

	public:

		void setup();
        void update();
		void draw();
   
    
    int radius;
    
    int top;
    int myleft;
    
    float secondsAngle;
    float minutesAngle;
    float hoursAngle;
    
		
};

Check out these posts for similar issues …

2D line endings with thick lines are sometimes troublesome.
Check out the shivaVG renderer which draws lines more smoothly at the cost of some performance & OF compatibility:

Thanks! If I had found that thread on my own I would probably have dismissed it…

Thanks for the tip, 'preciate it!