Quote:
Originally Posted by Shiraz
surely you can? take any good set of dithered subs (maybe use 30? for convenience) that you already have that has reasonably sharp detail - use that as the starting point and stack them to generate a reference image. Then software bin those subs 3x3 to get an undersampled set of subs - and then 3x3 drizzle stack the binned subs to get back to the original scale. compare the drizzle restoration result with the original stack and see how much degradation there has been - and how much detail you can recover. That should tell you how much use 3x3 drizzle is.
your D700 may well have an anti-aliasing filter, which will limit the FWHM?
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That wasn't something I'd thought of so I have gone and done some testing, doesn't quite work as well as I'd hoped :/
I had been trying to figure out why I couldn't get more resolution out of my D700 but I had forgotten about that annoying anti-aliasing filter.
So my discovery so far. I started with a 33x600s stack of Ha on NGC 248, created a group of 2x2 & 3x3 binned images, registered and drizzled them different amounts.
The original FWHM is 2.262 pix.
The 2x2 binned and drizzled 2x2 has a FWHM of 3.175 pix which I found quite surprising as I was expecting it to be closer to 2.4 or 2.5 pix.
The 3x3 binned and then 3x3 drizzled ended up at 4.048 pix.
The 3x3 binned and then 2x2 drizzled and resized to match ended up at 4.174 pix.
I imagine things will work a bit differently in the real world. In my mind under sampling has a different effect to binning when light is hitting the sensor, just in the way flux is recorded and what not. Has been a good test anyway. Will just have to try a real world example at some point into the future.