Hi Jet486
A modded DSLR is one that has had the IR blocking filter removed and either left as is or replaced with a clear glass or more selective filter.
The prob is the standard IR filter cuts too deeply into the red part of the spectrum and reduces the ability for Ha emissions to be recorded. Removing it let this most desirable part of the spectrum to be recorded with less exposure time. Its not all good news though. If a suitable IR filter isn't placed over the chip too much IR can cause colour balance problems and 'soft' images. Also if the filter is removed and not replaced with the correct thickness of glass/filter the camera with standard lenses won't come to focus using autofocus.
Typically an image from a modded camera has a much more red cast than a non modded camera. This can be alleviated for normal shots by shooting a suitable white background under good illumination and using this shot to set a custom white balance. It will only work though in the manual settings. Shooting in preset mode will usually end up having red images
HTH
Edit: I've attached a single unprocessed RAW image. Only been converted to jpeg