We had hoped to combine our new data with data from 2013 and 2015, but the last two nights the seeing and transparency have been best ever for us, to the point where the old data added nothing or made it worse, and the old stuff has been consigned to the outer darkness.
Full size image here.
Luminance 7 hrs in 1 hr subs, RGB 2.5 hrs per channel in 30 min subs. Aspen CG16M on 20" PlaneWave.
Mild deconvolution on L, then very strong arcsinh stretch, meticulous setting of zero point on each channel to foothill of histogram. Colour is almost as it came out of the camera, excepting for a slight increase in blue, and a large increase in saturation. Last of all, lashings of wavelet sharpening. Doing that after the nonlinear stretch seems to produce the least artifacts.
NGC 5128 is accepted to be a dusty edge-on spiral (meat pattie) being gobbled up by a much older giant elliptical. Consequently, we would expect to see intense blue dots around the edges of the meat pattie, representing bright young stars at the collision zone. We would also expect to see the sesame seed buns being orange hued (not blue or white) because they are composed of extremely old stars with no new star formation.
The relativistic jet from the central black hole heads off toward ten o'clock. Two parts are visible. The inner part, well within the sesame seed bun, comprises a bluish chain-o-ponds. The outer part, well beyond the bun and extending to the top left corner of the image, comprises discrete intensely blue dots and patches, and several very faint but quite visible complex continuous arcs, reminiscent of a solar prominence tracing magnetic field lines.
The faint ring structure in the outer halo is not well seen in this single night of L. We might be able to see it if we combined the image with that from previous years. If you download the original image and increase the brightness, you can see hints, but more interestingly, you can see very faint blurry extensions to the galaxy heading off toward top left and bottom right, a bit like a pair of Noddy-style night-caps.
There are a surprising number of distant galaxies visible given the closeness to the Milky Way - we counted 30 with distinct morphology - including five or six seen straight through 5128 itself.
Rather happy with what we got, after a month-long nightmarish technical drought.
We can never go too deep on this one. The 1.5 to 1.8 sec arc seeing was pretty rough compared with say New Mexico, but we'll be thrilled if we an get more nights with conditions as fine as we had here, and try to get more on the rings and particularly the jet. .
NEW 2 June 2017
We've now doubled the exposure. 16 hours of Lum, and 5 hours per channel of RGB, for a total of 31 hours observing time.
New full size image here. Of course doubling the exposure produces only incremental rather than game-changing improvements, we think it is better.
The background is now much less gritty. We've processed it to bring out the very faintest details in the faint lobe toward ten o'clock or so, at the expense of overall punch.
In the outermost extensions of the relativistic jet, you can see a wide and diffuse super-faint red jet with much brighter and sharper, but still faint discrete blue blobs and arcs.
Although the absolute colours are somewhat arbitrary, we can see that the outer halo is relatively pink, indicating older cooler stars, and the inner core relatively blue, indicating hot young stars. We've not done anything naughty or selective to produce that differential effect.
We've been very careful to produce as much contrast as we can in the meat pattie without burning anything to black. There is now more dark detail in the very darkest dust lanes in the meat pattie.
The distant background galaxies are a little clear and more definite now.
In a separate exercise, we've shot 7 hours of H-alpha. This has proven so ridiculously faint that, sadly, it has not been possible to combine it with this LRGB image, and we will publish it separately. However, it confirms all the features in the outer jet that we've described here: a broad fat H-alpha stripe with tiny, discrete sharper streaks and dots and arcs that here show up as blue.
Best,
M & T