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...
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.
Very nice. Don't quite see the $ but more of a rubber ducky to me
Not of course a commonly imaged target so all the better to see
Thanks for sharing
PS I wish I had some way to go 900 secs without auto guiding !let alone 1200
Thanks Narayan. Yes, like most target names, some require imagination to see. You are right that it does look rubber duck like. Perhaps the theme of July is ducks or duck season. Thanks for taking the time to check it out.
Like you Jase; I am a mega data convert. Nice setup by the sounds of it but I can understand sorting issues.
Really interesting looking object and will have to look around that area to attend to a few objects worth my consideration.
Thanks Paul. Set up has taken a while, thats for sure. I followed the information from Brad Moore's 2010 AIC presentation (Optimizing your Imaging Train) to 'hyper-tune' the system, in particular mount (pec,tpoint,balance) and collimation info. Good information that comes from experience. As mentioned in the original post, I spent considerable time on collimation. The Tak collimation scope only got me 85% there. Probably good enough but I wanted more. I like the method he suggests in MaximDL for even distribution of energy. Also, I had considerable effort in balancing the scope. Despite pier modifications, its a tight fit in the 2.3m Sirius dome, so I needed to set the OTA well back on the PME dovetail and use counter weights to balance in DEC. Its all come together relatively well. I'd say I'm where I want to be, limited by the seeing as opposed to the equipment... AO will likely be the next evolution of the set up but I'm in no rush at this point.
Quote:
Originally Posted by Stevec35
Nice shot Jase! Have to say I can't see a dollar sign though.
A beautiful nebula and excellent image Jase, nicely done.
900s unguided sounds like a dream, it must be great to have your setup running so well!
I'm upgrading to a 12.5" soon so I'll be tinkering with my own setup for a while I imagine.
Cheers Mike. Does look like the superman symbol! Hadn't thought of that one. When you spend hours processing an image, your mind starts to play tricks on you. I think I came back to this image with fresh eyes around three or four times, but each time I continued to see the dollar sign. I'm probably just nuts
Quote:
Originally Posted by SkyViking
A beautiful nebula and excellent image Jase, nicely done.
900s unguided sounds like a dream, it must be great to have your setup running so well!
I'm upgrading to a 12.5" soon so I'll be tinkering with my own setup for a while I imagine.
Thank you kindly Rolf! What you put in is what you get out, as you and others well know. Tweaks do take time but its worth the effort. I wanted to keep guider corrections down to a minimum so being able to go unguided for long sub durations was important. Improvements in PEC were moderate (PME is already low), but most of the gain comes from Protrack with unguided operations. Looking forward to seeing some of your images with the 12.5". Uber data collection awaits... Thanks again for checking out the image.
Quote:
Originally Posted by Octane
Mate, it is so, so, so, so, so good seeing a new image from you. I thought we'd lost you to the astro doldrums.
This is speccy. I can see the dollar sign easily.
Looking forward to your next installment.
H
Cheers H! Yes, it has been a long time coming. Not quite back in full effect, but progressively getting back into it. With most of the equipment issues addressed, I can now focus on the more fun side of imaging, that is processing data. Thanks for taking a look and making comment.
Interesting little neb, Jase. Nice to see it in situ in the wide field as well. An impressive feat without guiding!
Cheers,
Rick.
Thanks Rick. Something different, that's for sure. Am looking forward to guided images again. Alas I've not yet had the time to work through ACP's rotated guiding configuration, but I'm keen to do so promptly as there is no way I'm going to recalibrate the guider every time the instrument rotator changes position angle. Its simply not an option across multiple targets at different PAs in an automated data acquisition process. Good news is that it looks easy to set up, just need some clear skies to configure and test on a few targets. Thanks again!
Hadn't thought of that one. When you spend hours processing an image, your mind starts to play tricks on you. I think I came back to this image with fresh eyes around three or four times, but each time I continued to see the dollar sign. I'm probably just nuts 
