Quote:
Originally Posted by RickS
I didn't think we were really disagreeing, Geoff 
Noise is an interesting topic, though. It's always there no matter how much data you collect (damn Physics!) We just do our best to hide it in the background by not stretching our data too hard.
Cheers,
Rick. |
Yes noise can never be totally eliminated but it can be reduced effectively as you know. Your point here about stretching is certainly why I do long subs and then lots of them to reduce the appearance of noise in each filter set.
Quote:
Originally Posted by strongmanmike
I think the word Turd is a rather exaggerated and perhaps more of a self justifying term really, there are plenty of amazing images out there that weren't compiled from mega data (check some of Leo and Marco Lorenzi's work for example) and may have had some noise reduction or other processing applied, there is a point of diminishing returns here too. To me mega data's real benefit is in surfacing very faint features, so really comes to the for when imaging galaxies or faint nebulae that have otherwise invisible features and perhaps the finest example of this type of work is that by Rolf Olsen, the king of mega data, he has revealed some hither too unseen features with the greatest exposure times of anyone yet he still has some noise in his images.
Mike
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You have a few basic misunderstandings here Mike. Rolf images still contain noise despite 75 hours simply due to sub length and stacking methods. Faint objects need extended subs to collect enough photons to build the signal. You cannot effectively manage noise given a certain size aperture by doing lots of short subs. It is a complicated equation to managing noise for any given system and any given object. Aperture plays a big part as does calibration. However general a 30 minute exposure will have greater signal by large margins over 5 minute or 10 minute subs despite the aperture size. The signal will beat down the noise level and when combined in a mega data set that noise will be nearly unapparent after a certain amount of subs for each filter set. It will be different for every object and every filter set. You cannot simply point to one persons results and suggest it is the same over the entire board.
With regard to noise reduction ideas: if you don't have the time to collect the data then you will most likely need to employ noise reduction to varying levels of success. I don't use noise reduction at all anymore as I can and do collect vast amounts of data simply because I can. I have expended the money and time to allow me to collect mega data. This is my personal choice and I understand that not all people have the time to stay up all night after night to collect the data needed to reduce the noise.
Everything in the end boils down to your individual ambitions and budget, but ultimately this is not a job but an adventure in producing art and showing the night sky as I see it.