Usage Of Long Exposure Modded Webcams

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Usage Of Long Exposure Modded Webcams

Postby Dion » Mon Oct 18, 2010 12:55 am

This information is specifically aimed at users of the Astronomy Shed modded cameras. The cameras have 3 modes of operation, these are as follows.

The simplest mode is simple webcam mode, in this mode you do not need to connect the serial lead, simply set the switch to webcam mode and use the USB lead. If you have the switch in long exposure mode for this, when you change webcam shutter speeds in your software of choice it will have no effect on the camera, so check this if you find you cannot adjust shutter speed.

For usage in the above mode, simply follow the tutorial here SPC900 Imaging


Mode 2 is long exposure mode, for this, the recommended software is "wxastrocapture" which is free software and works very well. Firstly, you need to launch wxastrocapure and from the top bar select 'options' then click the "LE Control Port" tab, it 'should' select the port for the camera automatically, in this mode, your settings should look like this :-

Image


Long exposure is an understated description really, since a standard webcam 'usually' only goes to a lowest shutter speed of 1/25th of a second, technically, anything over this is classed as long exposure, which then can range from half a second to minutes!

For instance, the following image was taken using a Tal 3x barlow and shows the Albireo double, on a 200mm reflector with a x3 barlow fitted, you'd be lucky to even see these with a standard webcam, this was a very short avi consisting of approx 4 second shutter speeds :-

Image


So even 4 seconds is technically classed as 'long exposure'


When in long exposure mode, on the wxastrocapture main screen shown below :-

Image


Tick the "long exposure" box on the left and select your exposure length, some experimentation will be needed here as it's all dependable on the target, but I suggest when learning you practice on bright stars and known doubles, progressing on to globular clusters and nebulas as you become more familiar.

MODE 3 AMP OFF MODE

As you become more experienced, you will be taking longer and longer exposures, as you do, you may notice 'amp glow'. Simplified, this is a glow created by the heat of the CCD when used in longer exposures, the effect is reduced somewhat anyway with Astronomy Shed converted cameras as they have passive cooling. Usually, amp glow looks a little like light pollution and most likely will start to appear from the top left of images. Sometimes it can be eliminated by taking dark frames which is a whole new tutorial but can easily be googled.

if amp glow is sterting to become a problem, you can engage the 'amp off' circuitry which will reduce it significantly. We don't want to engage amp off until it's necessary since the amp off modification works by reducing voltages, some of which also feeds the CCD of the camera, this will very slightly reduce picture quality, more on that later.

Every CCD chip behaves differently, they start to produce amp glow by different amounts and at different exposure lengths and can even be affected by ambient temperature, hence why this is adjustable in these cameras.

To enable 'amp off' you go back into the port settings of wxastrocapture as pictured above and tick the box that says "Use Amp"

NOTE, you cannot change port settings whilst a camera is in use, so go to "camera" in the top meu and select "disconnect", then change port settings.

Tuning your amp off module is a little time consuming, so prepare for this, what you need to do is adjust the trimmer with a very small screwdriver, through the hole in the case, what you want to be doing is tuning your camera so that you achieve an acceptable balance between image quality and degree of amp glow, once you've done this you should never have to touch it again, as i said earlier, amp off is a trade with image quality, not significantly so, but enough.

Hopefully, this will get you started on the path to long exposure webcaming, for more information or any questions, please use the long exposure webcam tutorial discussions topic in "tutorial discussions' section.

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Re: Usage Of Long Exposure Modded Webcams

Postby Dion » Mon Oct 18, 2010 1:13 pm

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Re: Usage Of Long Exposure Modded Webcams

Postby Dion » Mon Oct 18, 2010 10:00 pm

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Re: Usage Of Long Exposure Modded Webcams

Postby Dion » Tue Oct 19, 2010 10:59 am

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Re: Usage Of Long Exposure Modded Webcams

Postby Dion » Tue Oct 19, 2010 10:06 pm

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Re: Usage Of Long Exposure Modded Webcams

Postby Dion » Wed Oct 20, 2010 7:55 pm

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Re: Usage Of Long Exposure Modded Webcams

Postby altec » Wed Oct 20, 2010 9:06 pm

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Re: Usage Of Long Exposure Modded Webcams

Postby Dion » Fri Oct 22, 2010 3:47 pm

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