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Fireball Reports : 2015 August

As usual, the period around Perseid maximum produced a number of fireballs.

Moonlight and cloudy skies had severely hindered observations of the Perseids in early August, but from the night of Aug 10-11 onwards, many areas of the UK enjoyed clearer night skies.

 

Aug 11th  01:48 UT (02:48 BST)

The first, however, was not a Perseid. Richard Fleet (Wilcot, Hants) captured this image via his east facing camera on the morning of August 11th.

Few stars are visible in the image, but Richard knows the exact direction in which this camera faces and so was able to establish that the path of he meteor when traced backwards did not originate from the Perseid radiant.

 

Aug 12th  00:35 UT (01:35 BST)

The following night produced an impressive Perseid fireball at 00:35 UT.

The fireball was seen visually by Tony Markham (Leek, Staffs) during a Perseid meteor watch. He estimated it to be magnitude -4, seeing it pass through Cassiopeia. It left behind a train which persisted for 25 seconds, splitting in two lengthwise and then very visibly distorting as it faded away.

The fireball was also imaged by William Stewart (Ravensmoor, Cheshire), via his NE facing video camera and his image, showing the fireball passing between Cepheus (centre) and Cassiopeia (lower right), is reproduced here.

It is always good to have a DSLR image of a fireball, partly because the colour makes them look more impressive, but also because DSLR images are sharper than those typically produced by video cameras.

Although Peter Hill (Barton under Needwood, Staffs) didn't captured the fireball itself via his DSLR camera, he did capture an image of the train as it started to fade away.

The part of Peter's image (slightly processed via Photoshop) that shows the train is reproduced here. (the train is the streak to the left of centre - the large "fuzzy" path is cloud that was present in that area of the sky). The constellation of Ursa Minor, with Polaris at bottom right, can be seen in the lower part of the image

Note how the right hand side of the train (the part closest to the Perseid radiant) is green.

This is a feature often seen in DSLR images of Perseid meteors and is due to emission from oxygen that can only occur at altitudes above 110km, where the density of the atmosphere is very low.

At lower levels, this emission cannot be produced, although many meteors do go on to produce a green emission line from magnesium at these lower altitudes.

 

Aug 12th  01:09 UT (02:09 BST)

This mag -4 fireball was seen by Alastair McBeath (Morpeth, Northumberland) during a Perseid meteor watch. Alastair describes it flaring twice an leaving a train the persisted for 4 seconds.

 

Aug 12th  23:21 UT (00:21 BST on Aug 13th)

This fireball was also seen during a Perseid meteor watch by Tony Markham (Leek). As for the previous night's fireball, it passed through Cassiopeia and Tony estimated it to be magnitude -4. Once again, it had a very persistant train and Tony was able to follow it for 30 seconds as it slowy faded away. On this occasion it did not appear to distort as much as did the one of the previous night.

The fireball was also seen visually by Tom Banks (Cheshire) during a Perseid meteor watch. Tom's record of the fireball includes the comment  Wow!

Once again, it was also captured by the NE facing video camera of William Stewart (Ravensmoor).

William's image is reproduced here (the fuzzy path above the fireball was due  to an internal reflection withijn the camera). If you compare this image with that for the fireball at 00:35 UT, you will see that the two fireballs had remarkably similar paths against the star background !

For this fireball, we have two DSLR images, which are reproduced below: 

 

On the left, we have Alex Pratt's image (from Leeds), in which the fireball is located between Pegasus and Cygnus. On the right, we have Peter Hill's image (from Staffordshire), in which the fireball is moving through the far north of Cepheus (the bright star to the top left is Polaris). Once again, the green colour is apparent near the start of the trail in Peter's image.

Peter was also able to image the train as it slowly faded and one of his images is reproduced here. Once again, there is a background glow due to cloud. This indicates that there was indeed significant distortion of the train, although the detail was obviously less apparent visually and so not readily seen by Tony, who was located further north in Staffordshire.

Alex has compiled a  GIF animation showing the fade of the train as seen from Leeds. As can be seen, the train appears to rotate very significantly as it faded.

Alex and William both operate as part of the NEMETODE network. Several other members of the network also imaged this fireball and their images can be seen in the August 18th update on the NEMETODE home page .

Analyses of the images obtained by William and Alex have allowed them to derive the ground track shown here for the fireball.

The smaller graphs on the left show the decreasing altitude of the fireball and its reducing speed as it descended. 

As can be seen, it started at an altitude above 140km (well above the 110km height above which the green oxygen emission can be produced) and ended below an altitude of 80km. As is typical of Perseids, its initial speed was above 60km/s.

Additional reports of this fireball from Barrow, Stockport and (possibly?) from further afield can be found here

 

Aug 13th  02:51 UT (03:51 BST)

This fireball was seen by reported by two witnesses.

One was Tom Banks (Cheshire), who recorded it as a magnitude -6 Perseid in Cetus, near the end of his meteor watch.

The other witness was Rob Davies (Devil's Bridge, Wales), who saw it in his ESE sky.

Unfortunately, it seems that this fireball was not imaged, with the cameras of the NEMETODE network either not pointing in the direction to pick it up or, in many cases, having been clouded out by this time in the night.

Added by:  Tracie Heywood