Matching a CCD camera to your scope setup

[gregbradley]

I finally got my FLI ML8300 repaired recently and I imaged with it for the first time this last week.

I imaged M104 and I had also been imaging M104 with the Proline 16803.

I expected the ML8300 to show more detail as it has smaller pixels and being a smaller chip it would zoom the image in more.

I was surprised to find that the images were far less detailed than the ones from the 16803.

The 8300 chip is giving me .38 arcseconds per pixel and the 16803 .63 arcseconds/pixel.

If I understand current theory on sampling you want something like 3X sampling (minimum 2X) to get enough data.

So with say 3 arc second seeing then .66 would be ideal. Smaller than that then must mean the smaller 5.4um 8300 chip pixels are simply getting a smaller slice of the light available compared to the 9um 16803 pixels.

The QE of the 16803 is a bit better than the 8300 but not massively. The well depth is 5X better in the 16803 but I figured that only comes into it on brighter stars which saturate more quickly (which seems to work out in that its harder to get colour in the stars from the 8300 chip in a 10 minute exposure).

So the moral of the story is to match your camera and scope well otherwise you won't be maximising either of their performance.

Greg.

[Bassnut]

As I understand, OSC's interpolate full res for each colour over the chip res (since each of RGB is represented by 1 out of 4 pixels, roughly). I thought the interpolation was pretty clever and hard to pick. Your test is interesting, seems it aint that clever.

[gregbradley]

No these are both mono cameras, not OSC. It must come down to pixel size that is best suited to the focal length. The lack of full well depth doesn't help with star colours as bright stars fiarly easily saturate the pixels.

Greg.