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 Post subject: Webcams for full-disk solar & lunar imaging
PostPosted: Thu Apr 07, 2011 10:51 am 
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I'm currently experimenting with a Trust WB5400 webcam.
This uses a different (CMOS) sensor to the (CCD) in the Philips cameras, so although it's not suitable for long-exposure conversion, the larger sensor means that the whole disk of the Sun or Moon will fit on the chip when using my 400mm focal-length 'scope.
Here's a solar image which I took yesterday:
Attachment:
File comment: Imaged through 80mm f/5 refractor (fitted with white-light Baader AstroSolar filter) using WB5400 webcam: this is the full-frame (640x480 pix) result.
Best 30 of 100 AVI frames processed in RegiStax.

Sun_20110406_1039_56.jpg
Sun_20110406_1039_56.jpg [ 42.69 KiB | Viewed 6978 times ]

Unfortunately, the camera driver for WindowsXP doesn't give me full manual control, so it's a bit fiddly to get the exposure right.

Has anyone else tried any other webcams for this application, and if so how did you get on?


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 Post subject: Re: Webcams for full-disk solar & lunar imaging
PostPosted: Thu Apr 07, 2011 8:14 pm 
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Yes, it does get the whole Moon in too:
Attachment:
File comment: Full-frame image from 400mm f/8 refractor using WB5400 webcam.
100 frames processed in RegiStax.

Object_20110407_1917_19.jpg
Object_20110407_1917_19.jpg [ 18.79 KiB | Viewed 6971 times ]


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 Post subject: Re: Webcams for full-disk solar & lunar imaging
PostPosted: Sat Apr 09, 2011 1:20 pm 
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Just finished a successful test with the Trust webcam and the Coronado PST:
http://www.boltonastro.org.uk/Gallery/displayimage.php?pid=520&fullsize=1
After a few hours' fiddling, I reckon that for Hydrogen-alpha solar imaging the camera works better in black&white mode.
I took 100 frames exposed for the disk and another 100 with higher gain to get the prominences, and stacked the best 70 of each in IRIS.
Then I constructed a colour image using the prominences for the Red channel and the disk for Green (the colour-alignment control in IRIS came in handy here).

The only snag is that there are limited controls in the Trust camera driver, and the gain sometimes "fights back" when I try to set it manually!


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 Post subject: Re: Webcams for full-disk solar & lunar imaging
PostPosted: Sat Apr 09, 2011 3:15 pm 
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The Trust webcam also works well with our bigger Coronado 'scope:
http://www.boltonastro.org.uk/Gallery/displayimage.php?pid=521&fullsize=1
This is also a 400mm focal length (but f/6.7) so the image still fits on the webcam's sensor.
The image on the PC screen was brighter than with the PST, but didn't seem to have as good contrast (although that may have been due to some wispy cloud which came over later in the day?).


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 Post subject: Re: Trust webcam
PostPosted: Sat Apr 09, 2011 3:50 pm 
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Today's final test was to compare it in VGA (640x480 pix) mode as against the default 1280x1024 resolution.
Attachment:
File comment: Trust WB5400 in VGA mode with Coronado SolarMax60 'scope
CM60_640res_9Apr_pm.jpg
CM60_640res_9Apr_pm.jpg [ 32.92 KiB | Viewed 6959 times ]

It's a lot quicker (the image-capture and processing is four times as fast), and I don't think that it makes a huge difference to the final image resolution?


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 Post subject: Re: Webcams for full-disk solar & lunar imaging
PostPosted: Mon Apr 11, 2011 10:22 pm 
I have a small 4" refractor and would like to try and get an image of the sun through it........ What sort of filter do I need ? I believe its a kind of film and I just make one myself for the main apeture and the finderscope but where do I get this film from? ....... It's better to ask these sort of questions before I get the wrong stuff and end up blind or setting fire to my wooden table outside or something I guess.


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 Post subject: Re: Webcams for full-disk solar & lunar imaging
PostPosted: Tue Apr 12, 2011 7:27 am 
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I use the special AstroSolar film from Baader:
http://www.green-witch.com/acatalog/Astrosolar_Safety_Films.html
http://www.firstlightoptics.com/proddetail.php?prod=bsolarfilm
http://www.scsastro.co.uk/catalogue/baader-astrosolar-safety-film.htm
http://www.rothervalleyoptics.co.uk/a4-size-astro-solar_d502.html

You'll need to make a tight-fitting (so that there's no chance of it falling off accidentally) cap to go over the front of your 'scope from cardboard, and cut a circular aperture in it over which the film can be taped, as shown in these examples:
Attachment:
File comment: Keith's solar filter for a Newtonian: the aperture is offset to avoid the obstruction of the secondary mirror and support
filter1.jpg
filter1.jpg [ 20.03 KiB | Viewed 6946 times ]

Attachment:
File comment: My full-aperture solar filters. Note that I've fitted them to my finder 'scopes too.
filter2.jpg
filter2.jpg [ 11.14 KiB | Viewed 6946 times ]

And from the offcuts of these you can make several pairs of "eclipse spectacles" for visual observing.

More details will be given in our talk Observing and imaging the Sun at the 7-Jun meeting.


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 Post subject: Re: Webcams for full-disk solar & lunar imaging
PostPosted: Tue Apr 12, 2011 12:07 pm 
rwilkinson wrote:
More details will be given in our talk Observing and imaging the Sun at the 2-Aug meeting.


Are the June and August meetings the same or is this a mistake on the calendar page? Perhaps you're just doubling the chances of seeing some sun?


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 Post subject: Re: Webcams for full-disk solar & lunar imaging
PostPosted: Tue Apr 12, 2011 12:42 pm 
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It's the latter Antony.

When we used to meet at the TIC, we closed down in June, July & August.
But last year we decided to try monthly meetings over the "summer" months too, and these proved popular. We don't normally have programmed talks for these three sessions, although last year we welcomed a local Astronomy PhD student who told us about her research, and this year we'll hear what Peter has uncovered from scouring the Borough Archive. For the other sessions, we'll have a social gathering, casual solar observing and informal "show & tell, bring & ask" activities.

Maybe we'll have the presentation on safe methods for solar observing and imaging at the June meeting, since fewer Members will be away on holiday then.


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 Post subject: Re: Webcams for solar imaging - IR filter needed!
PostPosted: Tue Apr 12, 2011 2:21 pm 
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Today I discovered that although the Coronado has very narrowband filters, it lets through enough Infra-Red energy to upset the webcam!
So once I fitted it with an IR-block filter, things started to work better...
http://www.boltonastro.org.uk/Gallery/displayimage.php?pid=529&fullsize=1


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