Quote:
Originally Posted by RickS
Bert: can you explain how resolution is enhanced by this process? I can see how it could produce a smoother looking result by interpolating followed by averaging but I don't understand how it could produce a real gain in resolution. If I'm missing something please enlighten me.
Cheers,
Rick.
|
Rick when a single image is upsized it is as if it was taken with a sensor with smaller pixels.
When many dithered upsized images are then stacked. The inherent resolution of the optic is sampled at different positions. This is where the higher resolution spatial information comes from.
This only works if the optic has better resolution than the sensor.
With enough frames by upsizing by a factor of 1.5 my 4096x4096 pixel sensor is now effectively a 6144x6144 pixel sensor.
This does not come for free as noise increases.
To put it into some sort of perspective my sensor is 3.08" per pixel. The resolution of a single image is at best 2x3.08" or 6". By stacking at native pixel size this will improve slightly.
By upsizing by a factor of 1.5 we now have 2" per pixel and the resolution of a single image is 4". By stacking at an upsized size we get just a bit better than 4" resolution. We need to take into account seeing and tracking which can be as bad as 2" and is additive.
So can you see my cunning plan? I do not need to worry much about seeing like all the other astrophotographers at longer focal lengths. The PMX mount tracks better than 1" or far less than one sensor pixel.
In fact there is a very high end studio digital camera ($50k+) that moves the sensor relative to the optic axis by about a pixel and takes three exposures in very rapid succession at slightly different positions and this improves resolution.
Bert