jase
12-07-2007, 03:19 PM
Greetings All,
Well I have to say, astrophotography certainly tests ones patients. While the weather has finally begun to cooperate, I’ve had other technical difficulties which resulted in further frustration. After receiving the custom-made M72 threaded FSQ/STL tube adapter from Precise Parts, I needed to redo the flats frames and re-calibrate FocusMax (as the imaging train had changed in length). The latter is normally a straightforward affair, but I certainly had issues with creating a good focus V-curve. What I thought looked good was the opposite! This resulted in spending two hours collecting RGB data to finish this project only to find that focus was subtly soft. Arrgggg. I could have potentially still used the data, but I didn’t want to compromise my luminance efforts, so I started from scratch. In addition to this, I found that my original estimate of 5min subs was insufficient to balance the strong Ha data. After some fine-tuning, I re-created an improved V-curve model with eleven V-curve runs. My focus is once again sharp (sigh).
So without further ado, I present IC4628 for your viewing pleasure;
IC4628 in HaRGB (http://www.cosmicphotos.com/gallery/nebulas/index.php?path=./&page=0&img=IC4628%20in%20HaRGB.jpg&idx=1)
Quick words on the image and processing (don’t want to bore you now);
Total exposure time is 5 hours – Ha:120min, R:60min, G:60min, B:60min (all 10min subs). Many may recall my previous post of this emission nebula in Ha, well I reused this data as the luminance, however did not use DDP – manually stretch with levels and curves instead. As the title indicates, the final composite is Ha:[Ha+R]:G:B. The Ha data was considerably stronger than I thought and took some work to balance and keep detail. I was tempted to deconvolve the Ha data as it produces sharper stars, but reduces the fainter nebulosity which I felt was more important to maintain considering the size of this nebula.
Dark/Flat/Bias reduced in MaximDL then registered in Registar, and then (no and then) combined (median) in MaximDL (the usual). I saved the Ha and R as tiffs and loaded into PS – layered using lighten mode to create a Ha+R blend. Ha+R, G, B files then brought back into MaximDL for colour weighting. In addition, I created a standard RGB file in MaximDL which I used for selectively restoring colour. Three layers where then brought into PS – Ha, Ha+R:G:B and R:G:B. Ha set to luminosity, RGB selectively integrated (stars and specific nebula features) using the lighten blend mode. Flattened image then used an inverted layer mask to reduce noise in dim areas that lack detail. Finally, duplicated the background layer and created a high pass custom filter layer mask on the duplicate and selectively highlighted some of the details I wanted to bring out (dust lanes, bright features, globs etc). Flattened again and seasoned to taste. That’s about it. Not sure if I’ve seen the end of this. May rework with fresh eyes.
Thanks for looking, hope you enjoy. Despite the frustrations mentioned, I actually enjoyed seeing this come together the way it did. All comments welcome. :)
Well I have to say, astrophotography certainly tests ones patients. While the weather has finally begun to cooperate, I’ve had other technical difficulties which resulted in further frustration. After receiving the custom-made M72 threaded FSQ/STL tube adapter from Precise Parts, I needed to redo the flats frames and re-calibrate FocusMax (as the imaging train had changed in length). The latter is normally a straightforward affair, but I certainly had issues with creating a good focus V-curve. What I thought looked good was the opposite! This resulted in spending two hours collecting RGB data to finish this project only to find that focus was subtly soft. Arrgggg. I could have potentially still used the data, but I didn’t want to compromise my luminance efforts, so I started from scratch. In addition to this, I found that my original estimate of 5min subs was insufficient to balance the strong Ha data. After some fine-tuning, I re-created an improved V-curve model with eleven V-curve runs. My focus is once again sharp (sigh).
So without further ado, I present IC4628 for your viewing pleasure;
IC4628 in HaRGB (http://www.cosmicphotos.com/gallery/nebulas/index.php?path=./&page=0&img=IC4628%20in%20HaRGB.jpg&idx=1)
Quick words on the image and processing (don’t want to bore you now);
Total exposure time is 5 hours – Ha:120min, R:60min, G:60min, B:60min (all 10min subs). Many may recall my previous post of this emission nebula in Ha, well I reused this data as the luminance, however did not use DDP – manually stretch with levels and curves instead. As the title indicates, the final composite is Ha:[Ha+R]:G:B. The Ha data was considerably stronger than I thought and took some work to balance and keep detail. I was tempted to deconvolve the Ha data as it produces sharper stars, but reduces the fainter nebulosity which I felt was more important to maintain considering the size of this nebula.
Dark/Flat/Bias reduced in MaximDL then registered in Registar, and then (no and then) combined (median) in MaximDL (the usual). I saved the Ha and R as tiffs and loaded into PS – layered using lighten mode to create a Ha+R blend. Ha+R, G, B files then brought back into MaximDL for colour weighting. In addition, I created a standard RGB file in MaximDL which I used for selectively restoring colour. Three layers where then brought into PS – Ha, Ha+R:G:B and R:G:B. Ha set to luminosity, RGB selectively integrated (stars and specific nebula features) using the lighten blend mode. Flattened image then used an inverted layer mask to reduce noise in dim areas that lack detail. Finally, duplicated the background layer and created a high pass custom filter layer mask on the duplicate and selectively highlighted some of the details I wanted to bring out (dust lanes, bright features, globs etc). Flattened again and seasoned to taste. That’s about it. Not sure if I’ve seen the end of this. May rework with fresh eyes.
Thanks for looking, hope you enjoy. Despite the frustrations mentioned, I actually enjoyed seeing this come together the way it did. All comments welcome. :)