NGC 1365 in colour

[Placidus]

Here we've added 3.5 hours per channel RGB to our previous 7 hours of Lum. In addition, we've stretched it a tiny bit less, and done some more wavelet sharpening.

Big version here (https://photos.smugmug.com/Category/Astrophotography-at-Placidus/i-VKSRPrB/0/O/NGC%201365%20L%207%20RGB%203p5%20ea ch.jpg)


Brightest detail: We've managed to preserve the 5 tiny star-forming regions in the very innermost core, though they're a bit less obvious in colour than in mono. These are often burned out in other images. We think of them swirling ominously close to the supermassive central black hole, flirting with destruction, and eventually making the mistake of dividing by zero.

Middle brightness detail in the spiral arms: Not so wonderful here. Love to blame the seeing. Colours seem about right. Long chains of bright blue star-forming regions. Sadly, a 15 minute test shot in 3x3 binned H-alpha showed nothing of interest - very different to say NGC 300, Barnard's, or the Sculptor semi-dwarf.

Faint outer ends of spiral arms: Kinda pleased with these. We're showing both foreground stars and star-forming regions aplenty in these outermost regions that are also not usually seen. For example, see the more or less isolated extension to the bottom left spiral arm where it wraps around past a clump of bright stars to about 5 to 6 o'clock. Also, have a shufti at the top right spiral arm, which also shows many bright blue knots of new stars. The inner edge here (say at 2 o'clock) looks scalloped, like a lettuce leaf, with two deep dark bays or notches, and an intervening brighter tooth pointing corewards. This region shows a very distinct sharp inner edge which is not so often seen.

L: 14 x 30 min subs, RGB: total of 21 x 30 min subs. Field approx 30 min arc, 0.55 sec arc/pixel. Aspen CG16M on 20" PlaneWave CDK. All processing using GoodLook 64.

Very best,
Mike and Trish

[Atmos]

:thumbsup: MnT

I checked out the image before reading what you'd written and I had the same thought as you, Ha!! There are a lot of nice magenta regions in there, I was thinking that it could have been on the NGC300 level with all of the activity that appears to be in the spiral arms. Very active galaxy that's for sure.

[RickS]

Nice detail despite seeing and an excellent image, M&T!

[Andy01]

Crackerjack image guys, really pretty despite your percieved shortcomings - hard to beat that long FL & aperture for this stuff- well done!
Would love to see some colliding galaxies next please!
Cheers
Andy

[Stevec35]

Not bad at all.

Steve

[Ryderscope]

That's lovely MnT. Nicely processed. Appreciate the excellent description.

[billdan]

Another superb image M&T, you must be proud despite the perceived problems. Further to what Andy said, M51 would be nice through the 20inch.

Cheers
Bill

[Placidus]

Thanks, Colin. The H-alpha must be there. Perhaps a Fred Bassnut style 100 hour stint would do the trick.



Thanks, Rick.



Many thanks, Andy. There's no doubt that others get sharper images than we're getting. We're pleased with the detail in the faint bits though.



Cheers, Steve!

Best,
M & T

[el_draco]

Beautiful. Lots of background galaxies. The one at 11 oclock looks like a rogue Saturn!

[Placidus]

Thanks muchly, Rodney.



Cheers, Bill. To my chagrin, I had to look up M51. We tend to concentrate on southern things because we can get a good long run on them.



Ta, Rom. Spotted Saturn. What is interesting is the number of Magellanic or dwarf irregular galaxies. Perhaps they belong to NGC 1365? There's one about 75% of the way to 12 o'clock and two more at the left hand edge at 9 o'clock.

[alpal]

Nice image Mike & Trish,
It's an interesting galaxy too:

http://www.constellation-guide.com/ngc-1365-great-barred-spiral-galaxy/

NGC 1365 is the dominant member of the Fornax Cluster, a cluster of galaxies located in the direction of Fornax constellation (http://www.constellation-guide.com/constellation-list/fornax-constellation/). The galaxy is approximately 200,000 light years in diameter, which is twice the length of the Milky Way, and has roughly the same mass as our galaxy.

In 2013, scientists were able to measure the rotation speed of the galaxy’s central black hole, discovering that the supermassive black hole, which is about 2 million miles wide, rotates at nearly 84 percent of the speed of light, which means that the surface is spinning at nearly light speed.

[gregbradley]

That turned out very well.

Greg.

[Shiraz]

overall a very attractive image - pleasing to view.
The colours seem to have a bit more saturation than you usually use - is that due to the galaxy itself being more colourful?

[Placidus]

Thanks, Allan. The idea of something two million miles wide and rotating at 84% of the speed of light makes my driving seem quite chaste.



Thanks Greg.



Thanks Ray. We were quite influenced by your magnificent image, which is distinctly sharper and more contrasty than ours. I'm starting to find that making the image reasonably saturated (to the extent justified by the exposure and depth) is useful for spotting distant background galaxy clusters, because they tend to be very orange compared with nearby star clusters. However, that didn't help in this case. The other thing is I've always liked images of 1365 that veer toward having a warm orange centre, rather than toward the magenta and blue. But perhaps we've overdone it this time. :D

[cometcatcher]

That's unreal. The colour version is so nice. One can get lost in that background galaxy field too.

[Placidus]

Thanks, Kevin. Glad you like it.

Spent the day attending inexpertly to matters rural. Sky crystal clear for two nights, but observatory computer still cactus profundus. Tomorrow will swap it out for the spare.

[ericwbenson]

Lovely image, IMO you got the background just right, mostly smooth but with lots of faint specks from unresolved galaxies, really pleasing FOV.

I am curious though, do you know what the green ghost to the lower left of most of the bright whitish stars is from? One bad green frame?
Also what is the green+red pair of spots below NGC1365's nucleus and above the string of Ha nebula from, could they be related to above? Or RBI from a focus star?
I switched from FocusMax to PWI3 full frame focus a while ago to get away from focus star RBI, or I had to dither really big offsets.

Regards,
EB

[Placidus]

Thanks, Eric. You've solved a long-standing mystery.

Definitely RBI, and not just from the focus star but from every star in the image. Had a look at the raw subs. It's not just in the green. We dither a lot between subs. There's always a perfect but shifted copy of the previous image. We absolutely don't want to go down the infrared pre-flash path. We've looked very closely both theoretically and experimentally at the effect of that on noise, and it's not acceptable (NASA recommends only using IR pre-flash at chip temperatures below about minus 70). Since we know the between-sub dithering exactly, and know the guy who wrote GoodLook 64 (our image-processing software), we could predict the amount of ghosting and either partially subtract or de-weight those pixels in that image, but for the moment I think I'll just file it under "irritating cosmetic issue to be addressed one day".

Thanks again for that.

Best,
Mike

[marc4darkskies]

Wonderfully deep with very rich colours M&T. Lovely work! :thumbsup:
Personally I'd tone down the saturation a bit - but that's just me I guess.

[Placidus]

Yes, got a bit carried away with the saturation. A celebration of Spring, perhaps.

[ericwbenson]

I agree with the pre-flash decision, my camera has it but I don't use it either. What cooler temperature are you using? I do 30min subs for almost everything at -25C and don't see such ghosting on field stars. It could be the 'CCD lottery' unfortunately. Processing them out would be a chore, remembering the order of the subs to now the previous exposure position, etc, certainly only a nice to have.
EB

[Placidus]

Chip normally at -30C. The colder it is, the less strong the residual image, but the longer it takes to go away.

[gregbradley]

I don't use it either. Although I did see some affected subs the other night so I turned the camera off and let it warm up and then turn it back on and cool back down and the residual image was gone.

Greg.

[Placidus]

Thanks for that, Greg. I'm starting to design a program that will sit between calibration and registration. It will go through each image that we took in a session in chronological order, and have a go at guestimating the residual image at the start of each exposure. It will have just two parameters: the strength of the residual image and the time constant for the exponential rate of decay. One can then use the guestimate to automatically either correct the actual image taken, or provide a set of weights for ignoring particular parts of the frame when stacking. That second part will sit on the back burner as we're busy fixing cattle yards and buying steers at the moment.

[gregbradley]

Well that sounds pretty advanced.
It may just be my lack of testing but I have only really noticed RBI on bright objects.

I have only really seen it a few times. Once when bright jet lights went through an image, the other I was referring to was NGC253 and the image was repositioned in the frame and I could see a ghost image of the earlier 10 minute sub below the actual and copies of bright stars mirrored imaged after the meridian flip.

Greg.

[strongmanmike]

https://www.youtube.com/watch?v=37OWL7AzvHo :lol:



Now that I understand...you area a steering committee :D

[Placidus]

Now that I understand...you area a steering committee :D[/QUOTE]

:lol:

Sixteen black Angus steers arrived today. They're all looking happy, healthy, and quiet. Probably just waiting till we're not paying attention and then they'll eat us. Must photograph something in Taurus soon, to celebrate.

[Atmos]

Reminds me of the plot of Black Sheep :lol: