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    Re: Venus in daylight
    From: David Pike
    Date: 2020 Apr 9, 11:52 -0700

    Hello Adrian

    Nice to hear from you.  First, an apology for not being clear.  When I said high in the sky, I meant like ‘in the stratosphere’; the sighting angle was only about 40degrees like Venus at the time.  If it had been the ISS, which I don’t think it could have been now, the following might have worked.  Draw a circle radius 63.7mm for the Earth and another concentric one 68.5mm for the ISS.  Draw a line from the centre of the circle through the observers position up into the sky (the observer’s vertical).  Draw a line from the observer’s position inclined at 50 degrees (90-40) to the vertical.  Where this line crosses the ISS orbit, draw a line back to the centre of the circle.  I measured the ISS would have been very roughly five degrees or 300nm on the Earth’s surface in the WSW direction along the great circle joining the observer to the ISS’ ground position.  Such a left to right orbit is just possible to someone with a good imagination.  Around 14.15 UTC this afternoon might have been such a situation. However, it would very quickly change direction and race away from right to left as its path changed from north easterly to south easterly w.r.t the Earth.  Unfortunately, that wasn’t the situation yesterday at 18.40 UTC.  Then, the ISS was over SE Africa.

    You might ask me how I know?  Well whereas most ISS tracker sites seem to only want to tell you where the ISS is now and where it will be in future, this morning I found a site which will show you where it was at any moment since the day it was launched.  Try this site http://www.isstracker.com/historical .

    What was it?  I don’t think it was a bird.  Any bird flying that high in the UK would only do so as part of a migratory flock.  It might just have been a fighter at around 65,000’ if you compare one to airliners up at around 39000’, but even then, it looked small.  I think it was probably a met balloon, they can get to over 100,000ft before they burst, but you'd need access to yesterdays winds to check direction of travel, or a LEO satellite that was just happening to catch the light. DaveP

       
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