Curious Track?

[groberts]

Living not far from Gatwick and Heathrow airports planes are something of an accepted hazard for my astrophotography, even in the quieter times of Covid-19.  However, last night just before 10pm I got the strange result shown below on a 180 sec Luminance  exposure.  It has all the hallmarks of a plane with 4 x light traces but seems to have also imaged twice what looks like the tailfin - is this possible, never seen such a result before?  Due to its speed I won't usually see  the wings or tailfins but twice.  Very curious.

Graham 

 

Edited September 22, 2020 by groberts

[tooth_dr]

3 hours ago, groberts said:

Living not far from Gatwick and Heathrow airports planes are something of an accepted hazard for my astrophotography, even in the quieter times of Covid-19.  However, last night just before 10pm I got the strange result shown below on a 180 sec Luminance  exposure.  It has all the hallmarks of a plane with 4 x light traces but seems to have also imaged twice what looks like the tailfin - is this possible, never seen such a result before?  Due to its speed I won't usually see  the wings or tailfins but twice.  Very curious.

Graham 

 

Very interesting!

[wxsatuser]

Not sure where you live but around that time there was a Bombardier Global 5000 that came out of Stanstead
and flew directly south right over Gatwick at 21000feet.

This type of small jet has a high tail and the rear strobe which is on the tail cone most likely lit the tail from underneath.

Edited September 22, 2020 by wxsatuser
typo

[groberts]

Thank but not sure about that - assuming say any plane was travelling at say +200mph and this is a 180" exposure, surely it would just leave a trail and certainly not two images?  As mentioned, I get more than my fair share of planes flying through my images and I don't think I ever recall seeing the plane itself, only a trail of their fuselage and wingtip lights. 

Graham      

[wxsatuser]

I have never caught any part of a plane but get many trails as we are on inbound and outbound Gatwick.

Someone could most likely work it out from the speed, height and your sensor size/scope.
The strobes are most likely flashing at 1persec but this is not set in stone, it can go as low as 40/min I believe.

You won't see other planes or their parts on images as their strobes will not light any part of the fuselage or wings.
Most airliners rear strobes are well back on the tail, more than likely will not light the tailplane.

The aircraft in your image has the usual nav lights on the wing tips plus a belly beacon.
It also has the wing mounted landing lights on, these are on the wing leading edge just out from the fuselage.

BTW
This aircraft was travelling around 450>475mph at approx 21000feet over Surrey

[StuartJPP]

If you look closely at the trail there are actually 3 flashes though only two are clearly visible (the 3rd not quite in the middle of the other two).

I wonder if it is caused by patches of fog/mist lighting up the tail during the strobe flash? Though it can't be the aft strobe flash as that isn't visible.