The sunlit part of the moon is far brighter than the stars in the background. But cameras have dynamic range limitations. They cannot capture extremely bright and extremely dim objects at the same time. We can increase the exposure to reveal the stars, but then the moon will appear washed out, with no visible details.
Flat-Earthers use the lack of stars in photos taken from space to dismiss them as fake. In reality, the reason for the lack of stars is the same reason stars are also missing in photos of the Moon taken with the correct exposure.
The looney 11 rule is a rule of thumb to estimate the correct exposure to photograph the Moon: f/11, 1/100s, ISO 100, or equivalent. With this exposure setting, the Moon will appear in a normal brightness in the result. However, stars are much dimmer and will not be visible using the looney 11 exposure. The photographer needs to increase the exposure by about 15 stops to reveal the stars. 15 stops exposure increase means more than 30000× increase in light-gathering power. However, by increasing the exposure in such a way, the moon will appear washed out.
If stars are not visible in photos taken in space, then the exposure setting was not high enough to reveal the star. Is there another object in the photo other than the blackness of space? Is the object lit by the sun? If the answer to both is yes, then that’s the reason stars are not visible. The photographer was trying to capture the image of the object, which is much brighter than the stars.
References
- Equivalent Exposure Calculator to Compare Any Two Camera Exposures – Scantips
- Looney 11 rule – Wikipedia