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A few hours ago, I've taken 178 images of the Eagle Nebula/Omega Nebula area of the milky way using Canon EOS 5D Mark IV, iOptron SkyTracker, and Canon EF70-200mm f/2.8L lens.

As I'll be stacking around 180 shots, I've bumped up the ISO all the way to ISO 32000 and the photos are undoubtably noisy. However, when I was cycling through the photos with my friend, my friend spotted a white dot near the Eagle Nebula in only one shot. It's definitely not noise (see bottom middle towards a little right):

enter image description here

enter image description here

That dot is more than a single pixel, exists in one and only one photo, and has a something-bursting-in-two-directions like shape.

It's obviously not a plane, nor I think it's a satellite.

We are not pros in deep space astrophotography and maybe it's a very simple thing. But just out of curiosity: what is that dot?

UPDATE: I've highlighted the area of interest in the second shot. My settings are: 200mm focal length, 6s exposure, f/4.0, ISO 32000. The photo was taken at location 38.226838, 26.338415 and time 26.09.2017 23:11:34 GMT+3.

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    For future reference it would be helpful to highlight the area of the images you want people to see. In this case I had to scroll up and down a lot to try and see what you meant. – StephenG Sep 26 '17 at 23:30
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    What was the shutter speed of that shot / each shot? – scottbb Sep 27 '17 at 0:55
  • @StephenG I've added the area of interest. my bad, sorry. fixed it now :) – Can Poyrazoğlu Sep 27 '17 at 8:13
  • @scottbb I've added all the details. see my updated question – Can Poyrazoğlu Sep 27 '17 at 8:13
  • "It's obviously not a plane, nor I think it's a satellite." Not obvious at all, and you give no justification for this arbitrary assumption. A satellite is actually the most likely answer. Why would you think this is not a satellite? – Olin Lathrop Sep 27 '17 at 11:53
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There is this thing called Iridium Flare, it is basically sunlight reflecting on large surfaces of manmade satellites (https://en.wikipedia.org/wiki/Satellite_flare).

Those flares can be quite bright, maybe that is your spot. I think you can find calculators for your time and location of imaging to see whether there where any Iridium Flares visible.

  • At that sensitivity I tend to think an Iridium Flare photographed from anywhere near the center of the ground track would have been multiple orders of magnitude brighter. Certainly bright enough to have cause blooming over a much larger area than the light seen in the example. – Michael C Sep 27 '17 at 5:51
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    You are right. It might have been the edge, or just beginning or end of the flare though. It would help to know the shutter speed and also time gaps between the shots. Iridium and other satellites of course would produce a trail with long enough shutter speeds. – smow Sep 27 '17 at 7:47
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    since a tracking mount was used I'm assuming longer shutter times. – Michael C Sep 27 '17 at 7:49
  • @MichaelClark it's 6 seconds. see my updated question, I've added more details. – Can Poyrazoğlu Sep 27 '17 at 8:14
  • @smow I've used the following link: heavens-above.com/… it doesn't show any flares for yesterday night at anywhere those times – Can Poyrazoğlu Sep 27 '17 at 8:30

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