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[quote name='popo' timestamp='1316021545' post='11595']





While I'm here, anyone know what's going on up there? 100% crop. Kit: standard 600D, Astronomik CLS clip filter, 135/2 at f/2.8, 10s exposure.



Note on the brightest stars there is a red glow around them. At first I was wondering if this was LoCA, with red having a differing focus point than G+B. But if you split the image into RGB channels, the other red bits are as sharp. If I focus to minimise the red glow, everything else is out of focus.



My guess is could it be IR? Maybe the long exposure might be enough to pick some of that up on brighter objects, and with a different focus point appear as the red blob?



I have eliminated the filter as the cause. It still did that with the filter in place. I'm not sure if it got worse at f/2 or not, but it was similar enough.





Maybe purple fringing? Also known as 'sensor blooming'



Some sensor/lens combinations do it, some do not



Look at PZ test reports, eg Nikkor 180/2.8



Choosing a smaller aperture helps.



Just a thought

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