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I recently undertood the delicate task of removing the IR filter from my
Canon 350D and replacing it with clear anti-reflective glass in order to
increase the sensitivity of my camera to the hydrogen-alpha emissions
spectrum that is very prevalent in many deep sky objects. Was removing
the IR filter from my 350D worth the effort? I think the following images
of the Veil Nebula answer that question.
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| Before removing the IR filter. Single exposure, 5 min, ISO800, stretched |
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| After removing the IR filter. Single exposure, 5 min, ISO800, stretched |
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These two images are similar size crops of the same region of the Veil Nebula.
Both images have been converted from Canon raw format with daylight white balance,
contrast stretch (with identical parameters), scaled and save as jpegs.
Note that the greater amount of noise in the first image is due
to the higher ambient temperature on the evening that it was taken. It has no
bearing on the topic of increased sensitivity to hydrogen-alpha radiation.
After IR filter removal a Baader UV/IR cut filter was employed to reduce
unwanted medium and far infra-red radiation. This is an excellent filter with
very sharp cut-off after the hydrogen-alpha emission wavelength of 6563 A.
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