Quote:
Originally Posted by jsmoraes
Thank you for comments, andyc.
Let's start by the second note. Yes, your shot in high resolution, crop of galaxy, has much noise. Despite it the less resolution version is very beautiful, in color and shape of galaxy.
Yes, my hight resolution suffered much noise reduction.
We use Canon. Canon produce much noise in the red channel. Your high resolution, like mine, seems to be the real resolution of Canon. Therefore, both photos will show much noise.
Galaxies are difficult to shot. They are faint, we need much time of expositon (more than we did - 1 hour or so), a good clear sky and none, or low, light pollution.
The stars inside galaxy, with our equipment will be like clouds, and noise reduction did it. The internal borders and internal details can be enhanced, but the intensity depends of the noise rate. I prefer something more smooth than high-sharped, but as you said maybe my processing was a bit heavy.
note: my main problem was a strange lack of focus with this galaxy. It seems that at each click the camera had some movement due its weight. And I had more coma then normal.
It was not a good session of photos. As I having bad weather, with much clouds, by weeks, something was weird with my equipments. Today, Nov,19th I used it again and all seems to be normal.
note: many people don't like to show the hi-res because always it will show issues with the capture. A good and clean hi-res photo is unusual.
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On the contrary, I have found that high-resolution clean images are indeed possible with a Canon DSLR (see my recent NGC1365
here), however long integration times and lots of dithered subs are really needed for faint extended objects like galaxies to control the noise. I have further reduced the noise with my cameras by installing regulated cooling. This means that I can keep the noise reduction during the processing stage to a minimum. However to be fair, not everyone has option of cooling or the ability to go for the long integration times that I have been using with a permanent setup.
In the case of Jorge's image here with only 76 minutes of exposure, I suspect the noise reduction is necessary to keep a smooth image after stretching. In the absence of noise reduction, a heavy stretch will always show lots of noise if the integration is short.