Hi all,
Long time no image post! I've started to go over a few wide field images I had previously taken and targeting interesting features at a longer focal length. Am always up for a project steering away from the mainstream targets. There are several other targets on the list (weather and season permitting), including some around the scp which will be a challenge as they don't get much altitude and likely require mega data. Will still be fun trying though...
Anyway here's my rendition of
RCW120
The wide field image that prompted my return to the area can be seen
here providing a perspective of where the nebula resides in comparison to other key HII objects.
Perhaps the nebula should be known as the "Dollar Sign Nebula" given its structure. With a SHO palette I could even make it look green. Who wants to be in the red anyway?
About the scene
RCW 120 (aka Sh 2-3, Gum 58) is a HII emission nebula residing in the constellation Scorpius. The nebula is an expanding star forming cloud of ionised gas powered by a central star. The star's radiation interacts with the surrounding dust and gas, increasing the density of matter in new locations, triggering a fresh round of starbirth. RCW 120 is about ten light-years across, is located approximately 4,300 light-years away.
About the image
This is the first light image for the new set up, well not really new. Still the PME and Alta F16M but the scope is a 12.5" RCOS w/TCC2. Has taken considerable time and energy to get the system up and running with most of time spent on being meticulous with collimation. The 16803 seems to be the limit for the 70mm optical train. Still some additional work to be done it fine tuning the automated sky flat acquisition but it works ok for now, just not as efficient as it could be with the PIR in operation. I was without a guider for this image (needed servicing, thanks Peter for the repairs) but I decided to press on regardless with the clear weather about. Didn't seem to make too much of a difference with the broadband data, nice round stars. The PME is well polar aligned and a 300 point tpoint model with protrack enabled, getting 900sec unguided subs is a reality. I began to get minor star elongation at 1200s subs which some would still see as acceptable, but I wasn't happy. 900s is not long enough for narrow band data as this image shows. I had to result to noise reduction through object masking. It requires significantly more exposure time to pack more punch. Processed in MaximDL (Ha pixel math), CCDStack and Photoshop CS5. Usual workflow for [Ha+R]GB data with Ha data added to both red and blue channels - 80% Red, 15% blue works for me. All acquired 1x1, Ha 6hrs, RGB 3hrs each for a total of 15hrs.
Hope you like it! All comments welcome.
Cheers