Quote:
Originally Posted by JA
Wow - what an incredibly detailed history Seems like the 183mm has something of a real niche and is something of a giant killer. You mentioned that exposures anything above 2 minutes need accurate darks, that begs the question :If you are lazy can you do without darks for less than say 1-2minutes?
Best
JA
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I would have to experiment. But if you take an image and its a fairly decent exposure it seems to overwhelm the amp glow.
I just checked some 60 second exposures and there is no amp glow even when stretched except on the red subs but its the tiniest mount of amp glow and only when super stretched so really zero.
Exposures of 3 minutes would have only very slight amp glow but at the point you probably would want it removed. 2 minutes probably would still have no real amp glow.
I should add to my review a bit about the pluses and minuses of such small pixels.
2.4 micron pixels are so small that really to achieve the goal of 1 arc/sec per pixel, which is often considered an ideal image scale for most locations' seeing then that gives you something like an FSQ106ED 106mm aperture F5 and .99 arc sec per pixel.
In other words a shorter focal length widefield system.
On my AP Riccardi Honders 305mm F3.8 I am getting .43 arc seconds/pixel which is very low and would be considered oversampling. Oversampling consequences really are only a loss of some sensitivity. The plus is the potential for higher resolution if the seeing is good.
This is exactly what I have found. Firstly I find it quite hard to focus compared to my other cameras. The differences between shifted focus seem a lot less and it can be hard to tell if you improved the focus or not so I take bigger shifts in focus and compare those to narrow the in focus point more precisely.
But when the seeing is good I am finding it takes advantage of the good optics more than the other cameras and I am getting a bit more resolution on galaxies. But nights of poor seeing would be a waste of time as the stars would be too large.
Such a camera would be a waste on a large scope like the CDK17. It would be so far past being limited by the seeing that you would be wasting sensitivity too much.
In short it suits a shorter focal length setup best. 250mm F4 Newt images show that it shines with those.
Most APOs should do really well with it. Lens imaging would be very good, Redcat 51 should work really well with it.
The sensor is small so I get virtually no vignetting. I still use flats but you could get away with not using them.
These CMOS sensors do not like bias subtraction so no need for them either. Darks though do get rid of the amp glow when it does show itself so above 2-3 minutes darks are going to be needed.
So not a camera for everyone but in the right setup it would be ideal.
Greg.