Centaurus A - 15 Hours, 2.4m FL, Kalahari Desert, Southern Sky Gems Observatory

[Harel_Boren]

Hi guys,

This one was on my list of immediate suspects to be addressed in the new observatory ("Southern Sky Gems") as soon as we've installed it at the Kalahari Desert.

It's 15 hours (my longest integration time thus far), and I'm rather happy with the resolution and noise levels.

http://www.pbase.com/boren/image/160474142/original

I hope you like it, and any comments are, as always, very welcome.

Cheers,
Harel

[niharika]

:eyepop:ohhhh maaannnn
Loved it Harel

[topheart]

Very nice!!

Tim

[DJT]

Awesome! Great colours and detail. Top job!

[pvelez]

That is a beautiful rendition

Pete

[Paul Haese]

Nice work Harel, lovely colour and smooth as background. Excellent detail.

[multiweb]

Great shot .Monster scope. Do you guys get many Lions around after sunset?

[gregbradley]

Overall a very nice image Harel. A couple of points. The dust area looks a bit orange to me, its usually more yellowishbrown. You got the blue star forming areas really well. Better than normal. You got the jet, the dust patches all good. Your stars though need some work. They are all very fuzzy/hazy. Was there some high cloud? Perhaps exposure lengths may need to be experimented with. Its like the rings around the airy disc have too much energy in them. So that could be seeing, high cloud, focus, exposure lengths too long for the well depth, collimation perhaps, filters? Another approach would be to mask the stars out early in the processing before the stretching as they don't need as much stretching and that airy disc ring energy is getting stretched and you don't really want that. I have had this happen in some of my images with the CDK17 and a reducer and Trius 694 and occasionally with a FLI Microline 8300 with some scopes (not all). Shorter exposures is one approach but with relatively high read noise that can cost some faint areas. It may be a compromise about which is more important. What filters were these? I am wondering if the Astronomik filters are better in these types of scenarios as they have a set with higher UV correction which probably would help.

Also I wonder if its a camera issue as I have never seen this phenomena from a QSI 683 camera. It may be better tuned to the sensor than others.
Greg.

[Eden]

Fantastic work! :thumbsup: One of the better renditions of Centaurus A that I have seen to date.

[jase]

Great rendition Harel! Greg could be onto something regarding the stellar profiles. Perhaps sampling not ideal though heavily oversampled data loves deconvolution to tighten them up. Personally I don't mind the stars. Kind of gives the image a dreamy feel. I tend to associate soft stars with soft details but this doesn't appear to be the case with your image as the dust lane is revealing structure from all angles. Excellent. You could always bring out the PS liquify|pucker tool on the stars. Very powerful. Easy to bring a size 16 model to a size 10 so it can work wonders on stars. The only challenge is to keep star sizes relative to one another. Thanks for sharing.

[TimberLand]

Great job and good colour. There is always something in an image that needs to be improved, but I think you've got a good handle on it.

[Rex]

Hi Harel, absolutely fantastic shot. Gob smacking details shown, great colour, and smooth as silk back ground. Only very tiny thing I noticed, is a slight edge colouring of some stars. Perhaps an alignment issue between the channels? Anyway, fabulous image mate, well done.

[Harel_Boren]

Thanks Rex,
I'm happy you liked it.
Yes, there might be a sllight misalighment here, though when zooming in I can't really see its symptoms, so just let it be :-)
Cheers,
Harel

[Harel_Boren]

Thanks guys, and very happy you liked it.

Greg, re color, I didn't touch the color, just made sure that it's well balanced out of Pix. I think that it's quite loyal to the source, as I had been imaging the color frames as much as possible at zenith. The avg. humidy around 30%, and high transparency.

Regarding the star sizes - it's a somewhat oversampled system - 0.464 arcsec / pixel, so in long exposures the stars get a little bloated. However, if I'd shorten the exposures, I'd be losing the very tiny 2-4 pixel stars throughout the image. Overall, I like the varying star sizes, which help give a more 3D-ish feeling. But... it's eventually a matter of taste :-)

Thanks for looking and sharing these invaluable insights.

Cheers,
Harel

[Regulus]

Really, really nicely presented Harel. Good colour, definition etc. Just, very nice.

Trevor

[gregbradley]

Colour is always a hard one.

Interesting about the stars. Come to think of it when I have seen similar stars in my scopes it has been heavily undersampled as well.

Its not really a big deal and as you say its a matter of taste and effect.

Greg.

[strongmanmike]

Hey Harel, forgot to comment on this one :doh:...it's a really nice Centaurus A :thumbsup: yeah the bright stars look a tad blobby but so did they in my recent Cen A :question: (very poor seeing one night :mad2:) I do like the way you have handled the dust lane details, they look very natural.

Mike

[Shiraz]

it certainly is a very fine image Harel. The colour is convincing and it has lovely transparency that is difficult to obtain.

The stars look fine - we are largely at the mercy of the seeing when it comes to their size.

[Harel_Boren]

I'm really happy you liked it!

I seem to be developing some emotional attachment to this image :-))

Cheers,
Harel