Cheap Webcams

For those interested in imaging and image processing with DSLR, CCD, webcam or film.
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dean_kos

Re: Cheap Webcams

#11 Post by dean_kos » Wed Mar 16, 2011 9:49 am

Hey Ross, here's a question for you.....
Is it possible to take long shots of polaris with the star trails revolving around it with a webcam??
Do the long exposure times go up far enough to get these type of image and if they do does it really work as desired .... what you think?
I will experiment on the next clear evening and let you know what happens ....

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rwilkinson
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Re: Cheap Webcams

#12 Post by rwilkinson » Wed Mar 16, 2011 3:17 pm

I've not tried exposures of over 60-sec on mine, but if you turn the gain well down on the Camera Properties, you may manage a few minutes before the noise starts to swamp the stars? You'll also need to take some fresh dark-frames and flat-fields to get the best from this set-up.
Try with the original webcam lens and turn off the drive motor (so the camera's fixed) Take a series of images, and then add them without doing any Stellar registration.

dean_kos

Re: Cheap Webcams

#13 Post by dean_kos » Wed Mar 16, 2011 7:53 pm

Hiya Ross, yeah will give it a try see what i can come up with .... incidently, are the lenses with the webcam kit pentax ones ? the reason im asking is that i was enquiring on the equipment forum about having a braket made with an olympus mount and Dave replied and mentioned an adaptor that could enable me to use the exact same bracket and same thred plus the adaptor for my olympus lenses ...
I just want to make sure im getting the right adaptor for the thread y see ....

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rwilkinson
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Re: Cheap Webcams

#14 Post by rwilkinson » Tue Jul 19, 2011 9:47 pm

Morgan Computers have a half-price offer on the SPC880 webcams "for one week only":
http://www.morgancomputers.co.uk/produc ... 80-webcam/

dean_kos

Re: Cheap Webcams

#15 Post by dean_kos » Tue Jul 19, 2011 10:43 pm

How strange...... I came on here tonight to write the exact same post !!!! We must both be on the mailing list I guess ......

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rwilkinson
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Re: Philips webcam LX conversion

#16 Post by rwilkinson » Thu Jul 26, 2012 1:16 pm

I've just been testing a Philips SPC880 webcam on which I've done the long-exposure conversion:
test1.jpg
First, with the camera in Normal mode (Auto exposure) in daylight
test1.jpg (44.05 KiB) Viewed 7124 times
test2.jpg
Then in darkenss, where the Auto mode has wound up the Gain to 100% (so it's a bit noisy)
test2.jpg (35.25 KiB) Viewed 7124 times
test3.jpg
Next with the gain reduced to 50% (still at 1/25-sec)
test3.jpg (17.97 KiB) Viewed 7124 times
test4.jpg
And finally in LX mode - a 2-sec exposure with the Gain at 50%
test4.jpg (133.58 KiB) Viewed 7124 times

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rwilkinson
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Re: Cheap Webcams

#17 Post by rwilkinson » Sat Oct 27, 2012 7:46 am

Here's another test with an LX-webcam, just using a low-cost 80mm f/5 refractor.
This is a single 43-sec exposure:
0001.png
Raw single exposure
0001.png (600.67 KiB) Viewed 7071 times
And adding together 68 of these (plus 48 dark and 12 bias frames and 12 flat-fileds) produced this result:
m57_BAS103_400mm.jpg
Processed result
m57_BAS103_400mm.jpg (49.29 KiB) Viewed 7071 times
I used SharpCap to control the camera, and then IRIS to do the processing.

imartin

Re: Cheap Webcams

#18 Post by imartin » Sat Oct 27, 2012 9:22 pm

Ross, that is a very good looking image. well done. The stars look a good shape.

Ian

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rwilkinson
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Re: Cheap Webcams

#19 Post by rwilkinson » Sun Oct 28, 2012 7:06 am

imartin wrote:The stars look a good shape.
Well they were a bit "blobby" to begin with, but that's where the Richardson-Lucy deconvolution algorithm in IRIS comes in handy:
http://www.boltonastro.co.uk/forums/vie ... ?f=4&t=340

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Re: Cheap Webcams

#20 Post by rwilkinson » Sat Nov 16, 2013 10:49 am

I've recently been doing some more experiments with Philips webcams -both my original LX-converted colour SPC880 and also an LX TouCam with a mono CCD (donated by Dave R).
Using the WcRmac software: http://www.burri-web.org/bm98/soft/wcrmac/ I've been able to change their mode of operation to output RAW data, rather than letting the camera run its own internal compression and/or colour-conversion.
Then IRIS can do a better job of calibrating and converting the raw data-stream.

Here's a comparison of 128-sec dark-frames (done indoors, so the camera wasn't cooled to operating temp):
dark128_IYUY2.png
Standard dark-frame, where the camera's internal processing has smeared out every hot-pixel into the adjacent positions in the CFA matrix.
dark128_IYUY2.png (446.94 KiB) Viewed 6037 times
dark128_YUY2_RAW.png
New dark-frame using the RAW mode: here the individual hot-pixels can be much more easily corrected using the dark-frame and cosmetic-list.
dark128_YUY2_RAW.png (238.67 KiB) Viewed 6037 times

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