M42 was one of the first astronomical objects I ever tried to photograph. I attached my Nikon D200 to my 5" Meade Achromat, and took a single 30 second frame at ISO 800. I knew nothing about darks and flats and stacking and such, but I was so proud of that image! Little did I realize what a challenge this object is, just because it's so bright.

This nebula is easily visible to the naked eye, even from within the town where I live. It's hanging down from Orion's belt, and at 1,300 light years distance it is one of the star factories nearest us. A multitude of stars are forming or have formed in this cloud of hydrogen. Four of them form an intensely bright cluster right in the middle of the brightest part of the cloud. The power of the radiation from those four stars has carved a cavity in the cloud. The bubble of gas and dust around the cavity has "popped" to expose the flourescing hydrogen inside.

Photographically, M42 is notoriously difficult to capture. The brightest parts of the nebula are thousands of times brighter than the faintest parts. Multiple exposures of different lengths are required to fully capture the detail across the entire nebula. These exposures are then combined using a technique called High Dynamic Range (HDR) processing. Many HDR images of this beautiful nebula look pasty and flat. They lack the depth... the glow... that make them truly captivating. I've tried to avoid that with this image, sacrificing some detail contrast for the 'feel' of the brightness difference between the inner, outer, and extended envelope nebulosity. I'm not sure I achieved my goal with this, but I learned a lot about how HDR works.

This is my very first attempt at an HDR rendition. I used exposures of 30 and 240 seconds. I didn't use specific HDR tools to combine them, because I find I can use the tools better when I understand the underlying principles. Sooner or later I'm sure I'll let Photoshop do the heavy lifting on images like this, especially when I have more than two exposure layers.

Version N introduces 1.1 hours of data for the bright interior of M42 and M43 from the 17" Planewave.

As I acquired the test images, and then the data I would use, I was baffled at first by the streaks across the image to the south of M42. They looked like satellite trails, but there were so many of them. I finally realized that the geosynchronous band runs right through this field. I don't yet have enough subframes for the sigma clip to weed out these trails. Next clear dark night, I'll see if I can get a couple dozen more subframes, which should be plenty enough to get rid of those defects.

Image acquired at Prairie Sky Observatory and Sugar Grove Observatory, facilities of Twin City Amateur Astronomers (tcaa.us).