On Thu, Dec 27, 2018 at 10:23 PM Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
On Thu, 27 Dec 2018, Ben Brockert wrote:
The star tracker is less useful if it only works when the thing it is
attached to has no roll. Stacking frames is effectively the same as a
longer exposure which, as Henry mentioned earlier in the thread, leads
to star trails rather than brighter stars.
There's one difference between longer exposures and stacking frames: you
can do shift-and-stack operations -- shifting frame N+1 around to look for
the best correlation with frame N, and *then* stacking -- instead of just
stacking. Correlation can work effectively even when the features it's
matching on are buried in background noise, so you don't need to be able
to distinguish the stars clearly in each frame to do shift-and-stack.
This doesn't eliminate the problem, but can reduce it significantly, at
the cost of a lot more CPU cycles (which are not free, especially in a
low-power device with a hard real-time deadline to meet, but are much
cheaper than they used to be).