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Originally Posted by Lester
Rich colouring there Paul.
Can you answer this question? Doesn't the modified Canon camera have the IR cut filter removed to capture more of the infra red range which is in most diffuse nebula. So by putting a infra-red cut filter back in front of the camera would undo to some extent what the modification was meant to do.
Hope you can understand what I am trying to say. It is just a thought I have come across, that I cannot answer.
Your photos as always are excellent.
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Hi Lester,
Yes I understand what you are asking.
The primary idea of modifying the Canon is to let the camera see 100% of the H-Alpha wavelength (red nebula). The standard camera blocks about 80% of that wavelength and about 100% of infra-red.
After I modified my camera the resulting images showed 100% H-Alpha (wonderful!) however the images also appeared much redder than normal. Even stars appeared much larger than pre-modification.
As it turns out this was happening because the modded camera could now see well beyond the H-Alpha wavelength into the infra-red spectrum and that means the stars "bloat" from excess radiation. I think the sky itself is also a IR heat source which is probably responsible for making the image backgrounds appear more reddish in colour.
Enter the Baader UV/IR Cut filter - it blocks the IR light from about 7000A and above, which is well above the important H-alpha 6562.8A line in the spectrum - so 100% of the H-Alpha light gets through to the camera but excess IR is cut-off.
hope you understand this, heres a link
http://www.baader-planetarium.de/dow...uvir-Cut_e.pdf for the filter.
thanks for your comments
Paul M