NGC 6960 The Witches Broom

[darditti]

Another result of multi-night imaging with the C11/Hyperstar/QHY8, here is the Witches Broom section of the Veil Nebula. This was taken over 5 nights from 18 June to 2 July. in 37 x 5 min. subs, from Edgware, 10 miles from the centre of London, combating not only the LP but also the permanent twilight of midsummer, moonlight, and general fug. 8 darks, 20 flats and 20 flat darks were used.

Processing was in DeepSkyStacker and Photoshop CS4 with GradientXterminator. The gradients/colour casts were in fact difficult to remove and I have not necessarily achieved the best possible result.

It's an interesting view as it shows how the Broom separates a much denser area of stars to the west from a sparser area to the east. I have no idea why.

David

(Click to enlarge)

[Deneb]

nice image, this is one of my favourites & so many stars..

[Rossco72]

Nice Pic. Like it alot

[James]

That's lovely! That's also no mean feat cutting through Edgwares orange glow. I hadn't ever noticed the difference in stellar concentration on each side either. Perhaps there more unilluminated dust and gas on one side compared to the other.

James

[Tim]

Nice result David. Getting rid of the gradients is very tricky when there are lots of stars, as here, but the broom has come through very nicely indeed.

I hadn't noticed the difference in stars, is it probably just an effect of the processing? I'll take a look at some widefields I have of the same area when I get home from work.

[minimalist]

Very good color and detail David, especially given the LP you must have. Balancing colors to me is probably one of the most difficult to do in such conditions. Very nice work.

Daniel

[darditti]

I don't think the difference in the density of the stars is due to processing. It looks to me as if perhaps the visible Witches Broom is the western, illuminated part (illuminated by the bright star?) of a larger gas cloud, most of which lies to the east (left), and is blocking out the stars. There seems to be a greenish hint of this in this image, but I am not sure this is not due to the processing. The stellar density seems to recover on the far left of the image to similar to what it is on the right.

I am fairly pleased with this picture, but I am not totally satisfied with the sharpness of stars I can get with the Hyperstar/QHY combination. I find it is impossible to get the stars perfectly sharp all across the frame no matter how much I collimate. I suspect the QHY chip may not be perfectly square to the camera, as I cannot eliminate some of the distortions at the corners (but they are never symmetrical). The distortions are tiny, but visible at 100% size. Being a perfectionist they still annoy me. The "full-size" image linked to here is only 50% size, so they are not that obvious.

David

[ollypenrice]

The difference you mention in the star count shows clearly in most images and is certainly not an artifact. The explanation that I have read is that the visible arcs (of which you show the Witch's Broom) are not the remains of the progenitor supernova but are the dust and gas swept out of the centre of the complex by the explosion. The sky thus 'swept' is far more transparent, hence the high star count. I also suspect that the sky just outside the arcs is rich in shock-compressed 'sweepings' not yet forming part of the arcs, and so particularly opaque. The second bit is just my own musing and so highly unreliable!

Great image.

Olly

[darditti]

Sounds a reasonable theory, Olly. I remember seeing this visually clear as anything from Les Granges. No chance of that from Edgware: I have tried.

David