Andre Vilhena
Member
Hello everyone,
I am creating a mosaic of Rho Ophiucus, one panel whose main features are the dark and reflection nebulas (top - P1) and the other whose main features are the orange and red emission nebulas (plus M4) (botton - P2) and I have noticed that on the bottom of the mosaic, the red hues are mostly lost, albeit they're present in the corresponding panel (P2).
For comparison, I have made a similar stretch and colour saturation on the pre-merged frame and on the same area of the mosaic (I created a preview of the area and separated it from the mosaic) - please see belo photo "PanelComparison", where on the left is the pre-merged frame and on the right the preview.
The frames were processed the following way: Crop, DBE, RGBWorkingSpace (1, 1, 1), MMT for noise reduction with inverted low contrast luminance mask, HistogramTransformation (slight stretch on each until the histograms match). Then, I used GradientMergeMosaic (Average) after registration to merge them.
Below I also attached the following histograms:
P1_Histogram - histogram of top panel immediately before merging
P2_Histogram - histogram of bottom panel immediately before merging
BottomMosaic_Histogram - histogram of the merged mosaic immediately after merge (of the area corresponding to P2 only)
As far as I can see, GradientMergeMosaic used a 100% transparency mask for the top panel and 50% transparency for bottom. Data was captured with an OSC camera. I have tried to merge with image still linear but the result is the same.
Does anyone have an ideia of what is going on that makes that loss of color? I would like to understand the reason behind but I'll also settle for a hint on how to repair.
Thanks and apologies for the long post.
Cheers,
André
I am creating a mosaic of Rho Ophiucus, one panel whose main features are the dark and reflection nebulas (top - P1) and the other whose main features are the orange and red emission nebulas (plus M4) (botton - P2) and I have noticed that on the bottom of the mosaic, the red hues are mostly lost, albeit they're present in the corresponding panel (P2).
For comparison, I have made a similar stretch and colour saturation on the pre-merged frame and on the same area of the mosaic (I created a preview of the area and separated it from the mosaic) - please see belo photo "PanelComparison", where on the left is the pre-merged frame and on the right the preview.
The frames were processed the following way: Crop, DBE, RGBWorkingSpace (1, 1, 1), MMT for noise reduction with inverted low contrast luminance mask, HistogramTransformation (slight stretch on each until the histograms match). Then, I used GradientMergeMosaic (Average) after registration to merge them.
Below I also attached the following histograms:
P1_Histogram - histogram of top panel immediately before merging
P2_Histogram - histogram of bottom panel immediately before merging
BottomMosaic_Histogram - histogram of the merged mosaic immediately after merge (of the area corresponding to P2 only)
As far as I can see, GradientMergeMosaic used a 100% transparency mask for the top panel and 50% transparency for bottom. Data was captured with an OSC camera. I have tried to merge with image still linear but the result is the same.
Does anyone have an ideia of what is going on that makes that loss of color? I would like to understand the reason behind but I'll also settle for a hint on how to repair.
Thanks and apologies for the long post.
Cheers,
André