Hi All,
Been having some “reasonable” weather of late, though not the best for imaging. High level cloud and fog to contend with – a real pain when its new moon. I’ve been spending a few hours refining the FSQ. Still have a slight field curvature issues. This should be reduced with the new tube extender from Precise Parts. Finally, got around to recording a good FocusMax V-curve so automated computer controlled focusing is now happening. Regularly get down to FWHM around 1.50 which I’m happy about. Still need to set up the temperature compensation. I’ve found that over the course of an hour the FSQ will have shifted focus by at least 30 to 40 microns due to temperature changes – not good when the CFZ is only 55 microns.
I have been working on stepping my images up a notch by carefully considering composition. Anyone can take a photo of a DSO object, but I’m looking to frame the object in aesthetic manner (where possible). Based on the western world, we read from left to right, top to bottom respectively. I look to frame an object in the top left of the field – this serves as a common reference point for the viewer to explore other objects within the frame. In this instance, its M20, but a bright star or cluster would also serve the purpose. I try to break the frame down to thirds across the field. The goal is to immerse/captivate the viewer and provide depth. It is clear when images don’t flow correctly. I have a few on my computer that will never see the public because of this. I will still use them for data on specific objects.
Anyway, I present two new images for your viewing pleasure.
M20 and M8 wide field
M8 – The Lagoon Nebula (100% scale - crop of the above image)
The image data was collected over two nights (struggled with clouds and fog). Total exposure: 160 minutes (L:70min, R:30, G:30, B:30). Luminance – 10min subs. RGB – 5min subs. I captured the blue channel when the object was close to zenith to mitigate as much blue extinction factor as possible. On reflection, I should have combined the L with Ha data to increase nebulosity and contrast. May collect more data on this another time.
Subs reduced (darks/flats) in MaximDL, registered in Registar and median combined back in MaximDL. Colour balance – R:1.35,G:1.0,B:1.65. Had some issues with PS curves on M8 – experienced white clipping as the nebula has a large dynamic range. I was going to use a multilayered approach allowing better control over the transition of brightness, but decided to use DDP in MaximDL to provide the non-linear stretch. MaximDL DDP by default also sharpens (which I didn’t want) so configured a custom 3x3 kernel user filter to ensure no sharpening was applied during the DDP stretch process. The L and RGB files were then brought into PS for final processing – unsharp mask and inverted layer mask for smoothing the dim areas.
Thanks for looking. All comments welcome.