Vertical object with red strobes moved in the northern sky from west to east.

We were outside trying to observe the ISS in the NW sky - did not see it but suddenly in the N sky about 40 degrees above the horizon we saw an object that was apparently vertical, red blinking strobes (back and forth, top then bottom, rapid succession, 6 times per second roughly?) - moved from west to east.  It appeared very large, but must have been enormous as it disappeared over the horizon in the NE sky.  The lower light appeared at about 30 degrees above, the uppermost light was at more than 45 degrees above horizon.