Color of sky at full altitude ?
Jan 9, 2015, 12:09 pm
#1
Original Poster
Join Date: Dec 2009
Posts: 552
Color of sky at full altitude ?
Well, I enjoy the view of colors of the sky during a clear sky flight.
This image I took on the KL597 flight over Libya shows a dark blue sky, but is deceptive. I used a 14mm lens on a full frame Canon, and on the ground such pictures can be taken as well.
What surprises me is that despite the air pressure is only 0.1 bar , so we are flying over 90% of the air, the blue shade is about the same as on sea level with a transparent air (i.e. no haze or mist).
I tried to find Venus inflight (which can sometimes be spotted by naked eye in daytime on the ground) but to no avail, despite the clear sky and the clear aircraft window.
But the difference I do see is that at nighttime stars on the horizon are virtually not dimmed due to the thin atmosphere. A Sun or Moon on the horizon shows white.
I wonder why the sky does not have a much darker shade of blue. Does somebody know this ?
This image I took on the KL597 flight over Libya shows a dark blue sky, but is deceptive. I used a 14mm lens on a full frame Canon, and on the ground such pictures can be taken as well.
What surprises me is that despite the air pressure is only 0.1 bar , so we are flying over 90% of the air, the blue shade is about the same as on sea level with a transparent air (i.e. no haze or mist).
I tried to find Venus inflight (which can sometimes be spotted by naked eye in daytime on the ground) but to no avail, despite the clear sky and the clear aircraft window.
But the difference I do see is that at nighttime stars on the horizon are virtually not dimmed due to the thin atmosphere. A Sun or Moon on the horizon shows white.
I wonder why the sky does not have a much darker shade of blue. Does somebody know this ?
Jan 10, 2015, 8:54 am
#3
FlyerTalk Evangelist
Join Date: May 2002
Location: Pittsburgh
Programs: MR/SPG LT Titanium, AA LT PLT, UA SLV, Avis PreferredPlus
Posts: 31,004
The sky will have a darker shade of blue at higher altitudes. Thinner air, less Rayleigh scattering.
This one picture has nothing to compare to (looking at the same view of the sky from a lower altitude), so you can't really draw a conclusion from it. The color/hue/luminosity/etc. of the sky at the same altitude/location varies over time. The conditions may have been such that there was more scattering than normal, so what you saw at altitude was like a "normal" view lower. But if you viewed that same location/time from lower, it would have been much lighter than normal.
This one picture has nothing to compare to (looking at the same view of the sky from a lower altitude), so you can't really draw a conclusion from it. The color/hue/luminosity/etc. of the sky at the same altitude/location varies over time. The conditions may have been such that there was more scattering than normal, so what you saw at altitude was like a "normal" view lower. But if you viewed that same location/time from lower, it would have been much lighter than normal.