This is Leo, the constellation, or better said, the asterism.
The image covers a field of 41x19 degrees approximately, and it's formed by 54 different subframes, that is, it's a mosaic of 54 frames. If you can recognize the Leo constellation, next time you're under dark skies, look at it – it's huge, and even larger than the Big Dipper or even Orion.
The first impression once one looks at this image is not the typical WOW expression, yet, this is one of those projects I've had in mind for several months already, and I really was looking forward to capture it and see it. In other words, I was not looking after any WOW effect, but simply going after a very challenging mosaic, driven by my interest in seeing this area of the sky at telescopic resolution, as opposed to using a camera lens.
The complexity of a 54 frames mosaic project means that extremely careful planning is a must, not only while capturing the data, but also during post-processing. The reason I mention this is because the planning for post-processing was a bit "accidental" which led to a few regrets once I was done post-processing the image, but correcting those "issues" would have meant going back to the beginning, before the process of stitching all 54 frames, a task I just wasn't going to repeat.
All the data for this mosaic was captured at a dark site I discovered near the Revolcadores peak in the Murcia region (southeast of Spain). It required me to travel to this point a total of 15 times, spending 15 nights at the site. Being at around 5000 feet and during the winter season, that meant dealing with temperatures between 32F and 14F degrees most nights (0 to -10C), not the coldest I've been, but certainly not warm, some of the nights, all surrounded by snow.
This was also my first large project where I not only used my trusted SBIG STL11k camera for the luminance data, but also my FLI Proline 11k OSC (color) camera for the color data.
As for the image itself, while I cannot be certain that each and every background intensity variation corresponds 100% with real variations – particularly in the transitions between frames - overall I'm rather confident that most variations are indeed data-driven and are not artifacts. This is not an excuse but, at least for me, stitching all these 54 frames and at the same time being able to preserve 100% accurate background intensity is extremely tedious, and at least in this case, it was quite difficult.
As a side note, if you've been familiar with the position of Mars during the first months of 2012, you would know that the red planet has been all over Leo. The way to avoid it was simply by timing the nights where certain frames were captured. I do have in fact a mono version of this image with Mars in it – quite distracting if you ask me :-)