Maximum exposure time to avoid star trails
- To take a starfield image without "streaking", the exposure time must be short enough that the star does not illuminate more than one pixel in the FINAL image.
- The smaller you scale your final image, the more pixels from the sensor will be summed up and small trails will not be visible.
- The calculator generates a table of maximum exposure times for a variety of focal lengths and target image widths.
- The last column is the full width of the sensor. The first column tells you how many sensor pixels are traversed by a star per second.
<< Enter some values or select a camera above to get the table here. >>
Q: I don't understand at all what's going on here?
A: Ok here's some random links...
Q: I have a XYZ fisheye, can you include it in the table?
A: No, I'm too lazy to do projection math just for fisheyes.
Q: Can you include my camera model in the dropdown?
A: No. Put in the values manually or get the Excel from below.
Q: Your calculated time is too short/long/ugly!
A: Probably, these are theoretical numbers and don't take into account things like:
Q: When I print this page, all the explanations disappear?!
- where you are & which part of the sky you're looking at
- Bayer demosaicing, microlens optics and other light->pixel translation quirks
- atmospheric disturbances or bad eyesight
A: Yes. On purpose. It fits nicely on an A4 paper that way.
Original JS calc: akikorhonen.org
This hack by vaizki @ IRCnet