One interesting thing about this sighting:
The object was initially at 230 deg magnetic and 1030 o'clock from the Hercules. That puts the a/c heading at 275 deg magnetic. The sun would have been lowish but still up, about 10 deg or so from FL200, a bit north of west, almost directly ahead of the plane. The object was off to the left and moving at a slow angular rate of about 7.5 deg/minute. It was a reflective slow-moving object described as like "an elongated sphere or dirigible", 8 deg above the horizon almost level with the sun and 45 deg left of the sun . It was evidently placed so as to catch bright reflections. After being lost to sight by the a/c commander it "reappeared twice" to some other crew "probably due to reflected light", an intermittency possibly suggesting rotation. So could this slow-moving object have been a big polyethylene balloon?
I don';t think so, because it was moving in the wrong direction. If they were passing a balloon the winds could be assumed to cancel for balloon and plane, being in the same airstream. We can assume this because unless they were quite close they could not have seen 15 deg of relative movement, and at 8 deg over the horizon (rather less above the observers' astronomical horizon from 20,000ft) it was not too far above their own altitude. Therefore in a C-130 at a cruise of about 290 kt they travelled about 10 miles during the 2 minutes and the bearing to a balloon should have moved left as it fell aft at roughly zero relative knots.
But it actually moved in the *opposite* direction, closing the angle off the nose from 45 deg to 30 deg.
Also, instead of growing in angular size as ought to happen with a balloon during this 2 minutes, it did the opposite and dwindled quite rapidly.
These two facts together suggest a real true motion towards the west.
We can estimate some other things about this: It was big enough in 12x bins to show quite a bit of detail. The description of 5 or 6 rectangular patches implies *at least* about 11 optical "bits" or elements of resolvable detail across it, probably more, each of which needs to have subtended at least a minute of arc, so we can be confident that the *minimum* true angular width of this thing is about 12arcmin/12 = 1 arcmin, which would be visible as a bright speck to the naked eye . So in closing the angle by 15 degs its bearing changed by about 15*60 = 900 times its own angular width in 2 minutes.
That has some implications, including that the *minimum* possible true metrical distance flown by the object in two minutes *relative to the C-130* was about 900 times its true metrical diameter. So, if it was 10 ft across (to pick a datum point at random) then it travelled nearly 2 miles, or a minimum of about 60 mph *faster* than the C-130, or about 320 knots. This is the minimum geometrically possible average rate, not the most likely average, and definitely not the peak rate, which would have occurred when it "shrank rapidly and disappeared to the SW very very rapidly" at the end of the 2 minutes.
Maybe it's possible to pull out something else from this about brackets on size, speed and distance (all coupled in known ways for conventional physical culprits) but I'm out of steam for this evening.
One other possibly relevant thing for completeness: There were no astronomical objects in that part of the sky. Venus was setting ahead of and NW of the sun, and the moon would have been a scarcely visible crescent also N of the sun and quite close to it. There was nothing else there in the W or SW to the left of the sun.
Date: Sat, 18 Aug 2012 10:37:55 -0600
From: Michael Tarbell <firstname.lastname@example.org>
On 8/17/2012 1:54 PM, Martin Shough wrote:
I've snipped off most of your excellent analysis to focus on this one aspect of the sighting that has me a little puzzled. The fact that there was some ambiguity about whether it was 5 or 6 rectangular patches leads me to think that, indeed, this feature must have been at the very minimum of visual resolution (i.e., one 'bit' each per dark patch and intervening light patch), otherwise there should be no uncertainty about whether it was 5 or 6. But in that case, how were they able to determine that the patches were rectangular, as opposed to say, circular? Identification of shape would seem to require substantially more 'bits' than the minimum assumed above.
As such I can only surmise that the object had substantially more angular diameter than the minimum discussed above, and that the individual dark patches were readily countable, but no explicit count was actually conducted, with "5 or 6" being a subsequent estimate from memory.
Yes, I think this is correct. I went through the same process of reasoning but returned to the conservative minimum on the basis that if visual memory could have been uncertain about the "four or five" it could also be uncertain about the shape. This may have been no more than a subjective impression in memory, based on some unstated assumption about marks glimpsed right at the limit of resolution.
But it is possible that the angular size was somewhat greater. I have the idea that only the observer with binoculars could see any detail (although this isn't too clear) but it would allow considerably larger angular scale. If the angular size was really great enough for five or six shapes to be separately and distinctly resolved as rectangles then it would need to be very much larger - at least 3 or 4 arcsecs across for each of 5 or 6 rectangles, i would say, with 1 arcmin between - and we are approaching the effective diameter of the full moon in binoculars. I think we can appreciate that this is large enough to see quite a bit of detail. 1/12 of this for naked eye size is only 2 or 3 arcmin, which is getting marginal for perception of shape.