DSLR cameras provide a cost-effective route into astronomical imaging, especially as the entry-level models are often just as capable as mid-level ones as far as astrophotography is concerned. However, their Achilles heel is poor sensitivity to deep reds. While not a problem when imaging galaxies and star clusters this greatly limits their ability to image emission nebula, whose light mostly comes from clouds of ionised hydrogen. The glowing hydrogen emits in a specific wavelength with a deep red colouration, and as much as 75% of this light can be blocked by the camera’s infra-red filter.
The solution is to remove or replace this filter. For the brave, there are various online guides for performing camera surgery yourself. Alternatively there are individuals who will perform this service for you. I had my Canon 1100D modded by Cheap Astrophotography and am very pleased with the result.
Here’s two images that show the difference that removal of the filter makes. The first shows Comet Jacques and the Double Cluster in Perseus, taken with the 1100D before modification, using a 135mm lens.
Comet Jacques is the green streak at the lower left, with the Double Cluster right of centre. Above and below the comet some nebulosity is faintly visible. The next image shows a very similar field of view taken using the same lens fitted to a modded camera.
Using the modded camera the Heart & Soul nebulae are clearly visible. The comparison is not an entirely fair one as the second image was taken at a site with very little light pollution, but in other experiments I've found it difficult to get much colour from an unmodded camera even from the darkest site.