Triangle craft headed towards Boeing Everett, WA facility

Day and time are approximate.  August 8, 1976, 11 PM.  
Was out in the backyard late at night with a telescope and binoculars looking for meteors during a meteor shower.  Skies were clear or mostly clear, low or no wind.  
Location Mountlake Terrace, WA, which is near Paine Field Airport near the Boeing Everett factory.   
Had observed the usual aircraft activity and seen several meteors.  My sister and I noticed a gently glowing object moving towards Paine Field, from our W-NW and moving north.  It was not moving very fast, and was rather low enough to see some details with binoculars.  
It moved in a straight line, no sound at all, and at a seemingly slow speed.  I had enough time to get my binoculars on it and study it.  It was not birds since it was well into night time.  
Definitely not an airplane.  Delta shaped, partially glowing from within.  It had a top ridge running down the center of the craft with a small protrusion out the back.  A faint white glow on top described a V line, but the rest of the craft was not very well illuminated.  
I wrote down the date and time on a piece of paper and included a sketch, but threw it away when my sister the next day refused to discuss the sighting, or even admit that it happened.  She was scared, so I became scared too.