Bright diffuse atmospheric phenomenon.

Bart De Pontieu (
Mon, 24 Feb 1997 18:51:25 +0100 (MET)

Hi all,

I received a message from Juergen Rendtel (
of the International Meteor Organization. I've included a
few excerpts below. If you want a text with the complete discussion
that was held on the meteor-observing mailing list, let me know,
I'll send it to you privately. It's a bit too long to be sent to

Suffice it to say that Mr. Rendtel contacted me (and I contact
you) because no explanation has been found yet. 

> 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 close to the 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 also from Potsdam, Germany (52.4 deg N,
> 13.0 deg E) 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              2 photos of the fireball patrol
>                                               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 don't expect an aurora-like phenomenon, because the Sun was quiet at this
> time and the geomagnetic coefficient Kp was very low.
> 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