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Thanks for your reply Ray.
With the 694 which is in regular camera terms a micro four thirds chip so if it were in a DSLR it would be a 2X crop factor compared to a 35mm chip like STL11.
So 1 metre focal length with that chip gives you the equivalent of a 2 metre focal length in terms of field of view or crop factor. 2 metres is a reasonable focal length for most people's seeing and to get a reasinable image scale on the larger galaxies (the smaller ones will still be small).
The well depth issue is a bit vague and shows up in some images and not in others. It seems to vary with the setup, the sub length and the focal length.
What seems to happen is a bright star saturates those shallow wells easily. Then as the star has a spread function the next pixels out overflow then the next and then the next. I realise the overflow is taken away. I don't know how perfectly these anti blooming channels work or if the microlenses have light scatter as well.
So the effect is on a bright star the number of pixels out from the centre that overflowed is much higher on these small well chips than the massive wells of the 16803 type chips. Hence the bloated looking overexposed stars. A better way of putting it would be these chips overexpose bright stars more easily resulting in nasty looking halo effects like say a Horsehead image with Alnitak in the frame. I assume the dynamic range calculation is simply read noise divided into well depth and the assumption there is it will display a wide dynamic range because the read noise is so low. That's a different concept to overexposure. DSLRs dynamic range varies with ISO. Its usually best at lowest ISO and falls off as you boost the ISO.
Couple that with a fast F4 and you will probably need to do short exposures to prevent blowing out the highlights ie. the bright stars.
The Bunyip scope - 12 inch (12.5 inch?) Newt has shown tremendous images and tends to support your argument except it is 12.5 inches or so and I would contend 12 inches is more of a sweet spot for most people's imaging situations.
694 versus KAF8300 is a different argument. 694 has smaller pixels, higher QE, slightly lower noise, but even lower full well capacity (the main worry for me - it may pan out to be not a concern though). 694 is smaller than 8300 chip in size (I think).
On paper 694 may be a winner if the small wells turn out to be no worry.
Another point as well. I bet the QE of these chips varies with the angle of the light hitting them. If too sharp an angle performance drops off on most chips heavily. Hence the microlenses on DSLR chips.
I look forward to your results as it will be an interesting cutting edge system. If you go for 10 inch I would go for super high quality mirrors.
Mark Suchting? Are you making the scope?
I notice the latest incarnation of CDK has 6 or 7 fans. 3 or 4 at the back and 3 at the side (I think just in front of the primary, no doubt to get rid of the thermal layer on the mirror more efficiently. That would be worth looking at.
Greg.
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