Frequently Asked Questions About Astronaut-Acquired Photographs

Questions about access to photographs:

North is not at the top of the photograph, is there some mistake?
The thumbnail and browse image look terrible, is it really that bad?
Why can't you see stars or galaxies in the photographs that show the curvature of the Earth and part of the black background of space?
Is it true that the Great Wall of China is the only human-made object that can be seen from space?
Where can I find a photograph of the whole Earth as seen from space?
Where can I find pictures of the Earth at night showing city lights?
How can I see pictures of Mount Everest?
Do the photos show the view exactly as it appears to the naked eye out the spacecraft window?

North is not at the top of the photograph, is there some mistake?

Astronauts take these photographs out of the windows of spacecraft, and the camera can be in any direction relative to the Earth. Because of this, North can be in any direction relative to the top of the photo. This is the nature of the photography and is not an error. To better interpret photos, you can print them out and then rotate the paper until North matches the direction on a map. After getting some practice, you will be able to rotate the images mentally to match them to geographic references.

The thumbnail and browse image look terrible, is it really that bad?

Because of the number of images that are added to our database each day, we cannot do publication-quality color corrections on each image. For some scientific purposes those corrections even destroy information (even though they make the picture look prettier). Our browse images represent an attempt to show what the film really looks like, and what the raw digital photo looks like. If an image is dark or colors seem unusual, color corrections using image software will make it look better. If you plan to use the photos in print or presentations, you will want to carry out the following steps in your software of choice: (1) rebalance the colors (2) adjust the image brightness, (3) enhance the contrast, (4) resize the image to the proper size for the application, and (5) sharpen the image.

Why can't you see stars or galaxies in the photographs that show the curvature of the Earth and part of the black background of space?

The reason you can't see stars in high oblique photos is that the film speed is too slow and the shutter speed is too fast. Most of the films used are 100 ASA color positive. Fast shutter speeds are used to eliminate blur from the motion of the spacecraft. These films and shutter speeds would not be suitable for photographing stars from the Earth either. One exception to this rule is when astronauts use films and camera settings specifically to photograph features such as the Aurora Borealis and Aurora Australis. In these cases stars also show up in the photograph. The photos are also slightly blurry because very long exposures are needed to capture these dim nighttime features.

Example photograph of the Aurora Australis that includes stars >>

Is it true that the Great Wall of China is the only human-made object that can be seen from space?

No. In fact there are many, many human-made objects that can be seen from space without magnification (browse our website for examples). These objects include buildings, mines, irrigated croplands, salt evaporation ponds, jetties and landfills along coasts, and yes, roads. Cities are easily visible, and at night, city lights. Of course, the further you get from the Earth, the fewer human-made objects you can see. Astronauts on the moon saw less detail when they looked at the Earth than astronauts on the Space Shuttle or Space Station see today. The most interesting part about the about the Great Wall of China is that astronauts cannot readily see it , even from low orbital altitudes . The wall is not that wide, and made from native materials that match the color of the surrounding landscape. It can be viewed using radar to create an image (the wall acts as a reflector), but cannot be seen on astronaut photos, even with a long lens.

Where can I find a photograph of the whole Earth as seen from space?

We like the image of the "Big Blue Marble" taken from Apollo-17. A private company called Arc Science Simulations has also made satellite composites that have been used in posters and museum displays. These aren't real photographs, but are combined from many satellite images to show what the Earth would look like if there were, for example, no clouds.

NASA has released a global set of satellite images from the MODIS instrument that also shows the whole earth. Products are available that have actual clouds, and have the clouds removed. See http://earthobservatory.nasa.gov/Newsroom/BlueMarble/.

Where can I find pictures of the Earth at night showing city lights?

Although astronauts sometimes take pictures of the Earth at night, their pictures only show small regions. NASA and NOAA scientists have made a composite form satellite images that shows the Earth at night. See an Earth Observatory Article on City Lights for more information. Nighttime satellite images from the Defense Meteorological Satellite Program are compiled on a website maintained by the International Dark Sky Association (http://www.darksky.org/).

How can I see pictures of Mount Everest?

We have an interactive tutorial that will help you see Mount Everest as the astronauts do.

Do the photos show the view exactly as it appears to the naked eye out the spacecraft window?

It depends on the lens used. Lower magnification lenses (< 90 mm) have a field of view that is more similar to what an astronaut can see when just looking out the window. Longer magnification lenses are more similar to what the astronaut sees when using binoculars to magnify and narrow the field of view.