"Satellight Pollution" of the Night Sky by SpaceX

Just a follow-up on how a time exposure can reveal things we can't see -- if you look carefully at the upper left corner, you should be able to see two meteor tracks. We could not see them at the time -- there was a bright moon. We did not even know they were there until we viewed the shot on the computer. This was about a 20 second exposure -- it was taken in the Boulder Mountains of Idaho, north of Ketchum and south of Stanley:


Click For Full-Size Image.

profdant139 wrote:

Based on absolutely no factual information, my guess is that the military folks have high ISO cameras that take flawless snapshots at night, but they are not releasing those tools for public use.

They would have to have large (diameter) lenses to do so, to collect more light. Current commercial camera sensors are, if my vague memory serves, somewhere in the rough neighborhood of 50% quantum efficiency; which means they could get at most about a stop better before hitting a hard limit of noise performance: that imposed by light being composed of discrete photons, and not actually being a continuous phenomenon.

As I understand it, a fair few modern digital cameras adjust the ISO purely in software, basically bumping the brightness on high ISO shots, without altering the sensitivity at the sensor level or in the readout circuitry.

One method used for low light & IR images is to cool the sensor with liquid nitrogen (-321°F). While this reduces noise, and is practical for telescope sensors, in might just be a bit of a problem for a DSLR!