Hi, no problem! I do not by any stretch claim any expertise in stereographic imagery, I just came to be interested in it for a little time, quite some time ago now. Just to clear up what I said which was apparently misunderstood (but maybe it's my fault, english is not my native language and I have sometimes hard time to express exactly what I'd mean
) : the stereographic effects comes from the shift of position of the object between the two images, but if the object is moving, it has to be captured simultaneously by the two cameras (which was obviously not the case for the "flying saucer"), in order for the shift between the two pictures to have a meaning relating only to the stereographic effect.
Actually, what struck me in the link was "In 2005, a researcher noticed that the second and third Heflin photos could be considered as a single stereographic image since Heflin moved in the seat between the two images" which is clearly not the case, and set my mind straight. But I must admit I read the thing quickly and I missed the main point.
If you look at the picture reflected by the rear-view mirror, you can see that Heflin centered himself towards the axis of the rear-view mirror but still keeping the camera oriented almost in the same direction (it seems that there is a small rotation to the left). So the movement would be mostly a translation forward and to the right (forward being the direction the camera is pointed to in the 1st photo). So even if the two pictures can't be used for some real stereograpic imagery, the overall effect of shifting between the two pictures could still show up, the shift being more pronounced for objects close to the camera. The fact that the shift of the "flying saucer" is of the same magnitude of that of the rear-view mirror one, when the trees in the far distance are almost lined up would indeed indicate that these two objects lie on the same plan. Now it could be said that between the two shots, the object has moved, which would false this assumption, but what would be the chance that the object moved in a way that the shift would be the same as the rear-view mirror one? Pretty low I'd believe...That's why I think it indeed indicates the object and the rear-view mirror are quite close.
I must also say that the object appears to me quite sharp and luminous (1st photo) or dark (2nd picture) to me, compared to the surroundings for its supposed distance as if a real "flying saucer" and the comparison with the poles somehow interesting.
For these (and others) reasons , I believe the Heflin photos are a hoax.