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 Post subject: Re: Cheap Webcams
PostPosted: 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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 Post subject: Re: Cheap Webcams
PostPosted: Wed Mar 16, 2011 3:17 pm 
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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.


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 Post subject: Re: Cheap Webcams
PostPosted: 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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 Post subject: Re: Cheap Webcams
PostPosted: Tue Jul 19, 2011 9:47 pm 
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Morgan Computers have a half-price offer on the SPC880 webcams "for one week only":
http://www.morgancomputers.co.uk/product_detail/10496/Philips-SPC880-webcam/


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 Post subject: Re: Cheap Webcams
PostPosted: 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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 Post subject: Re: Philips webcam LX conversion
PostPosted: Thu Jul 26, 2012 1:16 pm 
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I've just been testing a Philips SPC880 webcam on which I've done the long-exposure conversion:
Attachment:
File comment: First, with the camera in Normal mode (Auto exposure) in daylight
test1.jpg
test1.jpg [ 44.05 KiB | Viewed 6007 times ]

Attachment:
File comment: Then in darkenss, where the Auto mode has wound up the Gain to 100% (so it's a bit noisy)
test2.jpg
test2.jpg [ 35.25 KiB | Viewed 6007 times ]

Attachment:
File comment: Next with the gain reduced to 50% (still at 1/25-sec)
test3.jpg
test3.jpg [ 17.97 KiB | Viewed 6007 times ]

Attachment:
File comment: And finally in LX mode - a 2-sec exposure with the Gain at 50%
test4.jpg
test4.jpg [ 133.58 KiB | Viewed 6007 times ]


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 Post subject: Re: Cheap Webcams
PostPosted: Sat Oct 27, 2012 7:46 am 
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Here's another test with an LX-webcam, just using a low-cost 80mm f/5 refractor.
This is a single 43-sec exposure:
Attachment:
File comment: Raw single exposure
0001.png
0001.png [ 600.67 KiB | Viewed 5954 times ]

And adding together 68 of these (plus 48 dark and 12 bias frames and 12 flat-fileds) produced this result:
Attachment:
File comment: Processed result
m57_BAS103_400mm.jpg
m57_BAS103_400mm.jpg [ 49.29 KiB | Viewed 5954 times ]

I used SharpCap to control the camera, and then IRIS to do the processing.


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 Post subject: Re: Cheap Webcams
PostPosted: 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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 Post subject: Re: Cheap Webcams
PostPosted: Sun Oct 28, 2012 7:06 am 
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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/viewtopic.php?f=4&t=340


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 Post subject: Re: Cheap Webcams
PostPosted: Sat Nov 16, 2013 10:49 am 
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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):
Attachment:
File comment: 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
dark128_IYUY2.png [ 446.94 KiB | Viewed 4920 times ]
Attachment:
File comment: 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
dark128_YUY2_RAW.png [ 238.67 KiB | Viewed 4920 times ]


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