One of our members had been having trouble with a webcam which he'd converted for astrophotography, by fitting it into a 1.25" nosepiece, along these lines:
http://dslrmodifications.com/lifecam/lifecam1.htmlBut after the modification he found that he couldn't get sensible colours out of the camera.
Fortuntately, just before he slung it in the bin, he gave it to me to look at.
So I fitted it on the back of my 70ED 'scope and pointed it at some foliage in the garden:
Attachment:
File comment: The view through the unfiltered CCD
noir.jpg [ 15.4 KiB | Viewed 2436 times ]
Not a pretty sight!No matter where I set the white-balance slider, the colours were dominated by the red end of the spectrum - which gave me an idea. Looking into the front of the camera, I could see the unprotected CCD sensor, without the usual pink sheen of an IR-blocking filter.
So I screwed one of these filters
http://www.telescopehouse.com/revelation-ir-blocking-filter-1-25.html onto the front of the nosepiece and took another picture:
Attachment:
File comment: Looking at the same subject through an IR-blocking filter
irfiltered.jpg [ 15.25 KiB | Viewed 2436 times ]
Note that as well as giving a horrible colour-cast, the lack of filter would also give a blurred image of astro subjects through refracting telescopes, since they focus IR into a different plane than visible light.
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