NGC 3247 is a star-forming region in Carna called the Whirling Dervish. We see no Dervish. Instead, we see a cartoon-style bulldog (think Rough and Ready or Scooby Do, seen from above and behind) wearing a Madame Pompadour style hair-do and a very elegant and definitely whirling ballgown.
Seeing was good, and since we've started refocussing once an hour, and bolted some extra camera support on, we're getting sharper images. This is perhaps our sharpest image to date. Consequently the original full size image is a little large at 3.7 MB, but there's quite a lot of subtle detail - fine shock fronts, tiny pillars, finer dust lanes, etc - if you hunt around.
Unlike just about anything in the Magellanic Clouds, this region seems pretty gentle, as befits the Versailles ballroom, and there's precious little OIII or SII. We've tried not to force out what isn't there.
Red: SII (6hrs), Blue: OIII (6hrs), Green: H-alpha (4hrs), all in 1hr subs. Aspen CG16M on 20" PlaneWave. Field 36' arc, 0.55 sec arc/pixel. As usual, all observatory control and image processing software built/written in-house.
That is very sharp. What extra support did you install for the camera? Were you getting some flex in the focuser? Do you have the Hedrick focuser as the one on my CDK seems like a rock and is super heavy duty?
I can clearly see the Dervish (and his arms above and skirts below) that's a very interesting object, havn't seen that one before, very cool
Thanks, Andy. It's pleasingly different.
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Originally Posted by gregbradley
That is very sharp. What extra support did you install for the camera? Were you getting some flex in the focuser? Do you have the Hedrick focuser as the one on my CDK seems like a rock and is super heavy duty?
Greg.
Hi, Greg, yes it was the development of quite severe slop in the super-strong Hederick focuser. Was good out of the box. Possibly got too tight over winter and bent the casting. Our total load of camera, off-axis guider, and guide camera are within weight spec, and it's normally racked almost all the way in, so that should have helped. It flopped enough to produce severe camera tilt, and severe change of focus, as we tracked in RA. Could just order a new one I suppose, except it would probably just do it again.
Will take a photo of our stiffening apparatus and post it. It permits say +/- 5 mm of focus movement, but stops the camera from flopping about in RA.
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Originally Posted by SimmoW
Yeah, this is a rare case where I can actually see the object as named! Lovely detail team.
Thanks, Simon. I admit I can see why it is called a whirling dervish. The head is very bright, but the skirt is fainter.
It is very cool indeed, and 1h subs are also COOL ..
S2 is not far away from Ha, so to speak, images in Ha in LMC always produce more data, was there any particular reason why you decided to grab more S2 over Ha
It is very cool indeed, and 1h subs are also COOL ..
S2 is not far away from Ha, so to speak, images in Ha in LMC always produce more data, was there any particular reason why you decided to grab more S2 over Ha
Thanks, Ian. Not sure if by "S2 is not far away from Ha" you mean that they are similar wavelengths (true) or distributed together topographically (sometimes true, sometimes false). Addressing the latter point first, because H is easy to ionize, you get H-alpha in proportion to how much H there is, wherever there is a reasonable source of UV. Conversely, SII has two conflicting requirements to be seen. Firstly there has to be some Sulphur, and therefore old, dredged-up, recycled stuff. But conflicting with that, there needs to be very low gas pressure. You also need very hard UV or shock energy to excite it. Thus in really interesting regions (eg Gabriela Mistral) they are not co-located. In more boring areas, they may be.
Now on to the second question, which is probably what you were getting at. This object is pretty quiet, and therefore pretty sparse in both OIII and SII. Consequently we needed long exposures to see anything at all other than grit. Hope that makes sense.
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Originally Posted by Stevec35
Regardless of what it looks like it's a very nice image. Cheers Steve
Thanks, Steve!
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Originally Posted by RickS
I don't think I've seen this one before either. Very nice, Mike & Trish!
Thanks Rick. I guess it's not often photographed because it's a relatively quiet area, but it's rather pretty.
Been reading "An Introduction to Galaxies and Cosmology" by Jones MH, Lambourne RJ, and Serjeant S. An accessible undergraduate textbook. They explain how in an area such as around Eta Carinae, the stuff of the galaxy rotates FASTER than the density waves of the spiral arms, like speedboats overtaking a wave, or cars entering a traffic jam. Thus cold gas and dust moves into a star-forming region, and small stars start to form. You see a region a bit like the Dervish. Later, the region starts to produce whopper stars and supernovae, resulting in an OIII-lit cavity like Gabriela Mistral. Finally, you end up with a mature open cluster with no gas left, such as is visible at the extreme bottom left of the Dervish photo.
Ooooh yeah Mike and Trish, another "this was definitely taken with a big scope" looking image As you say lots of details everywhere..and I can haaaardly notice the decon
On the less aesthetic side ...it is a return to that dreaded green palette though
Anyway, the green doesn't take away too much from what is still quite a spectacular image
Hi, Greg, yes it was the development of quite severe slop in the super-strong Hederick focuser. Was good out of the box. Possibly got too tight over winter and bent the casting. Our total load of camera, off-axis guider, and guide camera are within weight spec, and it's normally racked almost all the way in, so that should have helped. It flopped enough to produce severe camera tilt, and severe change of focus, as we tracked in RA. Could just order a new one I suppose, except it would probably just do it again.
Will take a photo of our stiffening apparatus and post it. It permits say +/- 5 mm of focus movement, but stops the camera from flopping about in RA.
That's a bummer. Careful about removing the focuser as its shimmed to make it square. They didn't tell me that and the shims fell out. I put them back where I thought they were and everything seems fine.
I looked at this image in CCDInspector and it says there is quite a bit of tilt and collimation is off 3.1 arc seconds (not much). I don't know how much to believe CCDInspector although I noticed it can occasionally give inconsistent readings but its a guide.
At your focal length I would recommend a large Tpoint model and use the Protrack corrections if you are able to. I find it can take stars just that bit more to round.
Also try an infrared 750nm 25mm filter in front of your guide camera. Sometimes the guide stars are not bright enough but other times they are and I think that can help sometimes as well.
Ooooh yeah Mike and Trish, another "this was definitely taken with a big scope" looking image As you say lots of details everywhere..and I can haaaardly notice the decon
On the less aesthetic side ...it is a return to that dreaded green palette though
Anyway, the green doesn't take away too much from what is still quite a spectacular image
Mike
Thanks Mike We'll have a crack at some 2x2 binned starless SII and OIII over last quarter, and see if that helps us find where that elusive red stuff is, and balance the green without getting too gritty. There is more SII to be captured. Would love to understand what it's saying about the object.
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Originally Posted by multiweb
Really cool DSO Mike. Never seen that one before. TAK sharp field.
Thanks Marc!
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Originally Posted by Ross G
Amazing looking object Mike and Trish. A new one for me. So detailed and so sharp. Love the composition......and the imagination! Ross.
That's a bummer. Careful about removing the focuser as its shimmed to make it square. They didn't tell me that and the shims fell out. I put them back where I thought they were and everything seems fine.
I looked at this image in CCDInspector and it says there is quite a bit of tilt and collimation is off 3.1 arc seconds (not much). I don't know how much to believe CCDInspector although I noticed it can occasionally give inconsistent readings but its a guide.
At your focal length I would recommend a large Tpoint model and use the Protrack corrections if you are able to. I find it can take stars just that bit more to round.
Also try an infrared 750nm 25mm filter in front of your guide camera. Sometimes the guide stars are not bright enough but other times they are and I think that can help sometimes as well.
Greg.
Hi, Greg,
Thanks for the carefully thought and helpful reply, and the warning about the shims on the focuser.
I've attached a pic of the brace that we've added to stop the focuser flopping in RA as we track across the sky. The brace is extremely lightweight but very strong east-west. It reduces the amount of flop by a factor of at least five. I did of course do the maths to make sure that the focuser could still move in and out a good 5 mm (which is heaps) before exceeding the elastic limit of the brace! Colder weather should help further.
We use a reasonably elaborate pointing model. I think you've hit the nail on the head with camera tilt being the culprit. As long as the camera can flop about under gravity, fiddling with the tilt won't help. The current brace just prevents (most) east-west flop. We plan to replace it with a system that braces both north-south and east-west, and even more firmly.
The new system should also have fine adjustments to help with camera tilt.
To make this a bit more general for other readers, we note that we've found this sort of anti-flop arrangement to be useful on other scopes, even a Celestron C11, and on guidescopes and the like.
