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Bright diffuse atmospheric phenomenon at night
When turning on the fireball patrol camera this morning (1996 Nov 8)
I observed an unusual bright diffuse light high in the sky (almost
overhead). While it was overcast most of the night, I found that the
clouds started to disappear at 03:50 MET (02:50 UT). However, there
were slowly moving cirrus clouds as well as a few fast moving cumulus
clouds.
At 03:55 I was about to open the shutter of the camera, and I saw
`something diffuse' near zenith, i.e. north of Gemini. At a first
glance it appeared like the moon shining through thick cirrus or so.
(In fact, the moon was still below horizon.) I estimate the total
brightness of the phenomenon as -1...-2 mag, while I was able to
see stars up to +3/+4 with the naked eye. The object was elongated
(about 1 deg wide, 6-7 deg long), showed no motion, and even in a
10x50 binocular there was no structure to be seen. I took a few
photos between 04:02 MET and 04:14 MET. After 04:10 the brightness
decreased remarkably, and (also due to thicker cirrus again) it
disappeared after 04:15 MET. There was a little `knot-like' structure
around 04:12 visible in the binocular.
The position was near RA=100 deg, Decl=+40 deg, i.e. elevation 80 deg,
azimuth 15 deg (az. counted from S=0 deg).
I observed a similar phenomenon on 1987 Dec 21, 20:15 MET, and I checked
my log book for this entry. Here are some comparisons:
Date 1996 Nov 8 1987 Dec 21
Time 03:55 - 04:15 MET 20:15 - 20:35 MET
Position (elev.) 80 deg 85 deg
Size 1 deg x 7 deg 1 deg x 5 deg
Brightness when
first seen -1/-2 mag +1 mag
Remarks gradually fading gradually fading
position `fixed' position `fixed'
`knots' after some time no structure (visually +
phot.)
photographed (not yet 2 photos of the fireball
patrol
processed) camera
After the 1987 observation I first thought it was a persistent meteor
train.
But because of the remarkable stability of the shape and the duration I
was
very sceptical. Unfortunately, this was observed when the cloud cover just
started to break, so no photo of the fireball patrol camera from the
period
prior to the observation is available. This is the same in the new case.
There
is one difference: the appearance of the knot-like structure for some
minutes.
So, was this a persistent train of a fireball? Other ideas? Accidentially
(?)
both phenomena appeared close to the zenith - indicating a terrestrial
origin?
I am afraid there are no corresponding observations since the conditions
were
quite poor for astro-observers, and accidential eye-witnesses are unlikely
seen the time.
In the literature I found one old note which possibly refers to a
similar observation (I have to check the source, but it was in
`Astronomische Nachrichten').
Juergen Rendtel
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