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  #1  
Old 17-10-2017, 08:39 PM
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2nd mag naked-eye transient, Apus, 17th October

One of the oddest things I've seen in 25 years visual astronomy...

A bright star appeared just above Atria (alpha TrA), approx RA 17h 40m, Dec -69d 0m, at about 9:14pm AEST on 17th Oct, but faded below naked-eye as I watched over 15-20s. I didn't see it brighten, but it peaked a bit brighter than Atria, and was that bright as I was setting polar alignment on Atria, confusing me as an extra star near Triangular Australe. Observing site S Sydney.

No discernible movement at all (though naked eye, was watching carefully), so not a satellite flare or a plane. Much, much too slow and steady for a point meteor. Distinctly twinkling like other stars, so above the atmosphere. Nothing visible at the spot by the time I'd grabbed binoculars, 30s later. I'm an experienced observer, so would like to think (I hope!) I'd not be fooled by a satellite (though no movement and late evening) or a meteor of any kind.

Anyone else see anything? Or ideas as to what it was??
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Old 17-10-2017, 10:59 PM
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astroron (Ron)
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Quote:
Originally Posted by andyc View Post
One of the oddest things I've seen in 25 years visual astronomy...

A bright star appeared just above Atria (alpha TrA), approx RA 17h 40m, Dec -69d 0m, at about 9:14pm AEST on 17th Oct, but faded below naked-eye as I watched over 15-20s. I didn't see it brighten, but it peaked a bit brighter than Atria, and was that bright as I was setting polar alignment on Atria, confusing me as an extra star near Triangular Australe. Observing site S Sydney.

No discernible movement at all (though naked eye, was watching carefully), so not a satellite flare or a plane. Much, much too slow and steady for a point meteor. Distinctly twinkling like other stars, so above the atmosphere. Nothing visible at the spot by the time I'd grabbed binoculars, 30s later. I'm an experienced observer, so would like to think (I hope!) I'd not be fooled by a satellite (though no movement and late evening) or a meteor of any kind.

Anyone else see anything? Or ideas as to what it was??
I am confused with your time?
Your post was made at 8:39 pm
But you say you saw the flash at
9:14pm AEST? how can this be.?
I think it would be better and clearer
if you put local time and Universal time so
there is no confusion.
Now too the flash,it possibly was a satellite flair that was right on the edge of the earths shadow especially if it was heading southwest, and so by the time you had got your binoculars it had gone into the shadow.
It also could have been very high so you would have not seen any movement naked eye before it disappeared into the shadow.
Things that are closer too the poles don't show the amount of movement as those closer to the equator.
I have seen many long duration satellite flairs and what I have said here is usually the case.
Cheers
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  #3  
Old 18-10-2017, 12:33 AM
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Sorry, it should be AEDT - I'm guessing you're in QLD and an hour behind my location - Sydney, 10:14UT if you like. I've considered the satellite possibility, but it would have to be exceptionally high orbit to move so slow at that sky altitude (ie GPS sat height or so) but they're not typically that bright, even temporarily? Heavens Above shows no satellites in the right area at the time, though Meteor 1-29 passes not too far away a few minutes later... ultimately it's still the wrong place and time. It's not true that satellites closer to the poles show less movement - tilted and polar orbits have just as much movement across the sky; however satellites closer to the horizon or in very high orbits appear to move more slowly.

Probably was a high satellite somehow, in that it's the most rational explanation not involving v.v. unlikely flares from a red dwarf (can be big & brief) or a GRB (none reported, so that's ruled out!). I like a good mystery, and I've learned a bit about optical transients tonight.
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Old 18-10-2017, 08:13 AM
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OzEclipse (Joe Cali)
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Quote:
Originally Posted by andyc View Post
One of the oddest things I've seen in 25 years visual astronomy...

A bright star appeared just above Atria (alpha TrA), approx RA 17h 40m, Dec -69d 0m, at about 9:14pm AEST on 17th Oct, but faded below naked-eye as I watched over 15-20s. I didn't see it brighten, but it peaked a bit brighter than Atria, and was that bright as I was setting polar alignment on Atria, confusing me as an extra star near Triangular Australe. Observing site S Sydney.
Probably an irridium flare? Sometimes the flash is so brief so you barely see movement.
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  #5  
Old 18-10-2017, 08:17 AM
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I have seen similar transient a month or so ago, in Grus (or nearby).
It looked like exactly as bright meteorite, only there was no lateral movement across the sky.

I assumed it was a meteorite, moving exactly towards my location, and forgot about it
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Old 18-10-2017, 05:17 PM
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It may have been real !!

I was taking a sequence of images in h-alpha and recorded a remarkably bright and short burst (near M20) that is now being investigated by the transient team at Swinburne. Might even be part of a paper on this very contemporary line of astronomy research
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  #7  
Old 18-10-2017, 07:13 PM
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Most likely a satellite... have seen similar a few times in 50 years.
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Old 19-10-2017, 07:18 AM
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Thanks for the replies everyone. The elements of doubt in me as a scientist nag that it may well have been a satellite, even as my observational experience says I'd have seen it move over the 15 seconds or so at that sky altitude. And thanks Bojan and Peter for the other obs - transient research appears to be developing a lot as all-sky surveying increases in sophistication. I'll be very interested in the paper Peter, I just wish I'd had a camera pointed there myself. With hindsight I might've grabbed the dslr off the scope I use in polar alignment, get the lens on it and image quickly, but I didn't realise it would be so strange till it started to fade in place! Ah hindsight, leaves you with no data, just anecdotes...
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Old 19-10-2017, 12:54 PM
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Geo-flashers (flashing Geostationary satellites) are interesting critters that litter our sky and may behave as you have described. I've linked to a video of one I captured a while back.
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Old 19-10-2017, 01:22 PM
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Very interesting video..
In my case the flash was not geo-stationary satellite, the phenomenon was too far away from celestial equator (~-60).

As one of the suspects I also ( a bit later) considered Iridium flash... but my first instinct was meteorite, the light curve and the duration was just right - except it didn't move (or I was not able to determine if it moved or not).
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