Hmmm, the best way to have high s/n is have long subexposures rather than many subexposures. Using H alpha on sensors with CFA leads to 4 times resolution loss.
So I think the best way is 2 things: Monochrome sensor, and with cooling.
Eagle Nebula
Photo Album:
http://www.flickr.com/photos/14113965@N03/
http://www.flickr.com/photos/14113965@N03/
btw, have some queries about the composition of data... how was the initial HA component placed in RGB? The star sizes in the HA component should be a little smaller, hence when you combine it as a pure luminance, you will see rings around the stars, which seems to be the case in the first image. It will be better to blend the HA into the R channel component, so that you can have best of both worlds - the richness in HA for the nebulosity, and 'equalise' the star size of the HA fused into the star size evident in the R channel, in this case (HA+R)GB composite. You could do a little further from this composite, by using the HA+R component as a luminance layer to form a (HA+R)(HA+R)GB composite that will further enhance the stars profile in the overal image. Take note of the resulting after-effects of this method though, the salmon-pink effect which is both a loss of saturation and change in hue. You can combat this either by lowering the opacity of the 'luminance' (HA+R) layer or CTRL+U in PS to manipulate the saturation and hue sliders. Watch it though, don't overdo it! (as usual).
Another point of notice: The histogram profile for either images shows that the background is very dark (or perfect), with PS readings ranging from 0-2. Try to strive for a dark grey background instead (readings 10-25) or slightly dark-blue. This has a few advantages: you are able to see the subtle graduations in dim nebulosity in the outer regions of the Eagle or any other nebula, and you will also not clip or lose precious information that you have taken so much effort and time in undertaking!
If the result of the above gives rise to gradient effects then the initial image should have these gradients removed before doing this.
Another point of notice: The histogram profile for either images shows that the background is very dark (or perfect), with PS readings ranging from 0-2. Try to strive for a dark grey background instead (readings 10-25) or slightly dark-blue. This has a few advantages: you are able to see the subtle graduations in dim nebulosity in the outer regions of the Eagle or any other nebula, and you will also not clip or lose precious information that you have taken so much effort and time in undertaking!
If the result of the above gives rise to gradient effects then the initial image should have these gradients removed before doing this.
Yeah, this one is very nice. Wide-field with the nebula hanging in space with llots of natural looking stars.cataclysm wrote:Hi Vincent, thanks for the feed back. I am still trying to find the best 'blend' with the Halpha data. Here is another pic with Halpha data purely as luminance layer. I think the stars are more 'natural'.Nice pic, but I find the use of the filters too aggressive until all the stars seem red and the picture too "hard"
