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Visible from orbit?
Posted: Sun Aug 26, 2018 7:54 pm
by BDanielMayfield
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?
Bruce
Re: Visible from orbit?
Posted: Sun Aug 26, 2018 8:48 pm
by Chris Peterson
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.
Re: Visible from orbit?
Posted: Sun Aug 26, 2018 11:10 pm
by bystander
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.
Re: Visible from orbit?
Posted: Mon Aug 27, 2018 2:27 am
by neufer
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/
Re: Visible from orbit?
Posted: Mon Aug 27, 2018 2:34 am
by neufer
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