I am amazed at what a humble DSLR and 400 mm lens can do.
Each image is a composite of 16 exposures, 30 s each, f 5.6, ISO 3200, stacked in Photoshop and processed in Aperture. For M42 I layered a single 4-s exposure on top of the stack in order to show detail in the centre.
The camera was on an equatorial mount. I used a remote to avoid camera shake.
For comparison, the first image of M42 was a 51-minute exposure taken with an 11-inch aperture in 1880.