Visible from orbit?

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BDanielMayfield
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Visible from orbit?

Post by BDanielMayfield » Sun Aug 26, 2018 7:54 pm

This thread was prompted by this comment from the Aug. 26 APOD discussion:
visible-from-orbit man wrote:Holy cow! Visible from orbit? That's truly amazing. Or maybe not. I have a 30,000 lumen flashlight that can easily be seen from the ISS. Or from Alpha Centauri with a big enough telescope.
I found this guest commenter's handle to be hilarious, a literal lol. I mean, how rotund would you have to be ...?

Are any animals actually large enough for an astronaut aboard the ISS to see with unaided eyes? A blue whale perhaps?

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Chris Peterson
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Re: Visible from orbit?

Post by Chris Peterson » Sun Aug 26, 2018 8:48 pm

BDanielMayfield wrote:
Sun Aug 26, 2018 7:54 pm
This thread was prompted by this comment from the Aug. 26 APOD discussion:
visible-from-orbit man wrote:Holy cow! Visible from orbit? That's truly amazing. Or maybe not. I have a 30,000 lumen flashlight that can easily be seen from the ISS. Or from Alpha Centauri with a big enough telescope.
I found this guest commenter's handle to be hilarious, a literal lol. I mean, how rotund would you have to be ...?

Are any animals actually large enough for an astronaut aboard the ISS to see with unaided eyes? A blue whale perhaps?
Nope. A blue whale has a maximum length of about 30 m, and the ISS could be no closer to it than 400 km. That corresponds to an angular size of 0.27 arcsec, or about a half percent of the nominal 1 arcmin angular resolution of the eye. Of course, you don't need to be able to resolve something to visually detect it. If the blue whale was burning on a beach at night, the astronaut might see that.
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bystander
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Re: Visible from orbit?

Post by bystander » Sun Aug 26, 2018 11:10 pm

Chris Peterson wrote:
Sun Aug 26, 2018 8:48 pm

If the blue whale was burning on a beach at night, the astronaut might see that.
That's a rather extreme method of getting noticed.
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
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neufer
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Re: Visible from orbit?

Post by neufer » Mon Aug 27, 2018 2:27 am

Chris Peterson wrote:
Sun Aug 26, 2018 8:48 pm
BDanielMayfield wrote:
Sun Aug 26, 2018 7:54 pm
This thread was prompted by this comment from the Aug. 26 APOD discussion:
visible-from-orbit man wrote:Holy cow! Visible from orbit? That's truly amazing. Or maybe not. I have a 30,000 lumen flashlight that can easily be seen from the ISS. Or from Alpha Centauri with a big enough telescope.
I found this guest commenter's handle to be hilarious, a literal lol. I mean, how rotund would you have to be ...?

Are any animals actually large enough for an astronaut aboard the ISS to see with unaided eyes? A blue whale perhaps?
Nope. A blue whale has a maximum length of about 30 m, and the ISS could be no closer to it than 400 km. That corresponds to an angular size of 0.27 arcsec, or about a half percent of the nominal 1 arcmin angular resolution of the eye. Of course, you don't need to be able to resolve something to visually detect it. If the blue whale was burning on a beach at night, the astronaut might see that.
  • 30m/400,000m ~ tan(0.27 arcmin)

    2m/400,000m ~ 1 AU/1 parsec = tan(1 arcsec)
https://www.nasa.gov/vision/space/worki ... _wall.html

https://www.weforum.org/agenda/2016/07/ ... from-space

http://mentalfloss.com/article/57961/5- ... eally-cant

https://www.propertyfinder.ae/blog/4-ma ... -to-space/
Last edited by neufer on Mon Aug 27, 2018 10:40 am, edited 1 time in total.
Art Neuendorffer

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neufer
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Re: Visible from orbit?

Post by neufer » Mon Aug 27, 2018 2:34 am

bystander wrote:
Sun Aug 26, 2018 11:10 pm
Chris Peterson wrote:
Sun Aug 26, 2018 8:48 pm

If the blue whale was burning on a beach at night, the astronaut might see that.
That's a rather extreme method of getting noticed.
https://www.youtube.com/watch?v=4nTVrR0Gc5g
Art Neuendorffer