Quote:
Originally Posted by Dennis
Hi Al
In terms of the (slightly) grainy look, do you think that is due to over sharpening or perhaps just the relatively low number of frames you managed to stack from the sets of 500? I think that I once noticed a gritty look on my images with a low number of frames in the stack and this tended to lessen the more (good) frames I stacked.
I have noticed that really paying attention to the histogram in IC Capture paid dividends in choosing the optimum settings to record the best tonal range, even though its only an 8 bit camera and this gave me smoother looking images.
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Hmmm... I've never really thought of 100 frames as a "low number of frames" to be honest.
I understand the principle of the more you stack the better the S/N ratio so the smoother the image, and I usually watch the quality curve in the stack graph to be my guide.
I have stacked as few as 10 frames at times when the quality curve drops sharply at the left hand side. Generally I've experienced that during poor seeing when only a handful of frames are sharp. I would, of course, prefer to get at least 30 frames on the basis of 30 being the lower limit of any statistical validity for sample size (drawing on my uni stats
). I've done the experiment before to confirm to myself that stacking 10 good frames is better than stacking 50 or 100 mediocre ones...
It has been a long time since I've stacked 200-300 frames!
If I get a quality curve that's high and level from the left, it means one of two things: either the data is very, very good (and seeing was excellent) or the data is crap (poor focus, very poor seeing, etc) and will result in GIGO or at best a mediocre image after much effort (and usually downscaling
).
I will have a play with this data and let you know how I go though, Dennis
.
With respect to the histogram, I usually use brightness = 0, gain = 380 (I believe this setting optimises the dynamic range of the sensor. Merlin66 put me onto that one
) and then adjust the exposure to have zeroes appearing about the 220 mark to avoid clipping the highlights. Do you differ significantly from this, Dennis?
Al.