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 Post subject: Seeing the word through a rose-tinted webcam?
PostPosted: Fri Jun 17, 2016 7:12 am 
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Joined: Mon Oct 12, 2009 6:47 pm
Posts: 1277
Location: Bolton
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.html
But 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
noir.jpg [ 15.4 KiB | Viewed 3326 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
irfiltered.jpg [ 15.25 KiB | Viewed 3326 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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 Post subject: Re: Seeing the word through a rose-tinted webcam?
PostPosted: Fri Jun 17, 2016 8:06 am 
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Joined: Mon Mar 12, 2012 7:26 pm
Posts: 370
Location: Horwich
Well it was me.....

I'm convinced that I had tested it in daylight and used it for recording video from Jupiter, but being honest I carn't remember.

As I can not find the IR filter I took out I'm going to get the one recommended by Ross.

Bill


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