I see what you mean, but the photons are not necessarily appearing every second, and the subs aren't contiguous.
So if say a photon (drop of rain) arrives every 10 seconds or so, and your bucket is being emptied every other second (your chip is being read) then you may never collect those photons at all.
Also, if you were only capturing one photon, instead of 10 (with a sub 10x longer) then it would be harder to distinguish from the noise floor. With a 'quiet' sensor, this could make a big difference.
But I could be completely wrong, I'm only going on a thought experiment here, I haven't gone back to the books to get hard data.
Just doing some more imagining, sensitivity may be an issue, it might take a certain amount of photons to trigger a level change in that pixel on the camera, say it takes three photons within 10 seconds to push it over the boundary, if you had 5 seconds subs, only one or two photons would hit, and it would never 'click over' to the next level, so you would lose that info.
I'll try taking 60 one second subs and a 1 minute sub and compare the two.
Also, the longer the shutter is open, the more 'averaging' happens automatically rather than averaging later if you know what I mean.
If short subs could capture everything, then I'd be always doing one second ones, no aircraft or satellite trails to worry about
Surely someone has already given it a go.
There was a discussion here a while back on how to calculate the maximum effective sub time for your light pollution and camera, I'll try and find it.
Quote:
Originally Posted by multiweb
Hmmm.... don't completely agree with the above. If you think of your aperture as a bucket and photons as drop of rain you will collect as much water if you get the bucket out 10x60s or 1x600s.
The faint stuff might drop one or two photons per minute on your CCD but that will still compound as data vs. noise when you stack and increase your SNR.
The only disadvantage of having a lot of shorter subs in my experience is if your camera readout noise is important. Then 1x600s is better than 10x60s.
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