Antennae

[Placidus]

The antennae are quite faint, so the severe stretch required has made the background stars look a bit overweight. On the other hand, the massive star formation triggered by the severe tidal disruption has made the central galaxy exceeding colourful. We've actually reduced the saturation of this image a tad.

L 10 hrs, RGB 3 hrs each, all in 1hr unbinned subs. The thumbnail is a crop. The full frame is 36'arc. Aspen CG16M on 20" PlaneWave.

Big one here (http://www.mikeberthonjones.smugmug.com/Category/Astrophotography-at-Placidus/i-LM5RFPL/0/O/Antennae%20L%2010%20RGB%203hrs%20ea ch.jpg)

We very much want to at least double the exposure on this one but don't go out tonight, there's a bad moon on the rise.

[Andy01]

Wow, that's pretty. Love that swirl of stars coming off the right arm like they've been flicked off the galaxy. Sure must be a dim object if you're going add more after 19 hrs :)

[Bart]

As Mrs Brown would say, "That's fecken awesome" :lol:

[alpal]

The PlaneWave brings home the bacon again.
Well done.

cheers
Allan

[rustigsmed]

Yesss, that's great work team, is that about full crop? Fantastic image scale you get with that monster scope but of course you need good guiding to pull it off.
Thanks for sharing!

[RickS]

Very nice, Mike. Will be interesting to see what you can do with more time on it. You've already done a great job on the dim areas at the ends of the "antennae."

Cheers,
Rick.

[Geoff45]

MaskedStretch in PI may help here. Overall a very nice rendition of these galaxies. Someday I'll try to capture them. The big picture is really very nicely composed with good colour.

[Placidus]

Hi, Andy, Bart, Allan, Russell, Rick, Geoff,

Thanks for the encouraging comments and suggestions.

Will eventually master the art of a convincing star mask. That is still in my future light cone.

More in the realm of the possible, I particularly want to (eventually, one year) go very deep on the shape of the antennae, because different amateur shots show the "fluffy ends" quite differently. I suspect that they start to get lost in background artifact, and better flats, a crisp black night, a hearty 'Hi-oh Silver' and some 2x2 or even 3x3 binning is required to really nail their shape. The 20" front end will help, of course.

[Andy01]

Have you tried Startools? It has a pretty good star masking feature.

[Placidus]

Aye, there's the rub! It's fun to try them, to see what is possible, but for me the hobby is to only use software I've written myself, not just for image analysis but also for scope and camera control. That way I feel I've truly understood it.

Best,
Mike

[Paul Haese]

A huge image, lots to look at and with good colour Mike. Detail is good too, though I found this object a really tough customer. I think from memory I did 9.3 hours with an 8" and found it very noisy and still lacking detail. So by comparison your image is a masterly effort and very good already.

Just some minor issues. Your calibration frames might want checking as I can see coloured pixels in various spots. I have found this often happens when my darks are getting to around 5 months old. So maybe it might pay to check those.

Double your current exposure time is bound to achieve great results and I am looking forward to an even greater image.

[strongmanmike]

Wow, great view of this pair Mike and Trish, a great target for your big beast of a scope and I love the vibrant colours too, who processed that bit..? ;)

I see a lot of variation in the background, is that galactic cirrus? Even if it isn't it looks good anyway :D

Mike

[Placidus]

Thanks hugely, Paul. You are right about the darks. They are getting a bit stale. Even worse is some quite strange behaviour by either the 16803 chip or the way Apogee handles it. Each frame seems to have a dozen or so quite faint quasi-stellar bright spots. Not after-images (residual or ghost), not hot pixels, but something with an FWHM of about 2.5 pixels. But they are random. In the next shot, they will be somewhere else. I try to find them by automatically searching for spots that are only in one channel, and zapping them. New darks can only help, of course.



Thanks muchly Mike! The colour was a team effort. Pretty sure that the background variation is just dodgy flats. Did a complete new set this afternoon!

Very best,
Mike n Trish

[Stevec35]

Mike and Trish

Nicely done on this one. I do see some colour noise spots and it looks like your flats may not be perfect but still a very good image.

Cheers

Steve

[Ross G]

A beautiful photo Mike and Trish.

One of the best I have seen of this difficult object.

Amazing colours and detail but the composition is the stand out feature for me.

Ross.

[DJT]

Awesome image, MnT. Nicely framed, really like the saturation. :thumbsup:

[Shiraz]

very attractive image - can handle this level of saturation and looks quite spectacular. Stars look really nice as well.

[gregbradley]

Even worse is some quite strange behaviour by either the 16803 chip or the way Apogee handles it. Each frame seems to have a dozen or so quite faint quasi-stellar bright spots. Not after-images (residual or ghost), not hot pixels, but something with an FWHM of about 2.5 pixels. But they are random. In the next shot, they will be somewhere else. I try to find them by automatically searching for spots that are only in one channel, and zapping them. New darks can only help, of course.



Those would be cosmic ray hits which often look like a streak or a wormy streak.

These disappear with median combine as they are random as long as you have enough subs to make them clear as outliers.

Greg.

[Placidus]

Apologies, guys, I thought I'd replied to the last few posts, but the reply seems to have vanished. Perhaps I confused it with the other thread on the Dervish. Once more into the breach, dear friends:



Thanks, very much, Steve.



Hi, Ross, Chris Marklew posted a spectacular one the other day, which does the core much better, but I think the 20" PlaneWave has brought out more of the faint tidal tails, and, interestingly, more very faint stars.



Thank you David !!



Cheers, Ray, that's kind.



Thanks, Greg. The defects I'm referring to look exactly like little stars, and appear as super-saturated spots on the final image, much bigger than a hot pixel. Cosmic ray hits look quite different, as you say like streaks or worms. They appear as bright "stars" in the darks just as often as in the lights. Really seems like something wrong with the chip, but I'd prefer to work around it (as you say using statistical rejection) rather than send the camera back to the States and never see it again. Meanwhile, Trish and I took advantage of a really windy night and rattled off some more darks with the dome shut.

Best,
Mike

[SpaceNoob]

Damn fine job with those fainter parts, I tried my best to capture that stuff but I just couldn't get them to rise much above the noise, not sure if it's because I need more aperture, tiny pixels or because of light pollution. 30minute subs showed an average background ADU of ~4500 pointing West (towards the Brindabellas). The fainter extensions were around 10-30 ADU above the background for me. Pretty much clutching at straws trying to push them out in processing lol.

That 20" really sucks down those photons, are you at a dark site?

[Placidus]

Thanks kindly, Chris.

We're at a pretty dark site, midway between Orange and Wellington, 50 Km from either, and about 45 Km from Molong. The nearest house is 3km away. We're 660 m above sea level. There's nowhere around the Central West that is really high (like Mt Canobolas at 1300m) that isn't also a fog trap and cloud magnet.

A typical dark subtracted luminance 1 hour sub put the average for the entire length of the antennae at 3439 +/- 536 counts (mean+/-sd), and background at 3315 +/- 153 ADU counts. A difference of say 124 ADU counts or about 250 photons. The outer bits are of course proportionally fainter, but hard to tell where they end.

Best,
Mike

[NOMH]

Great job with this target! I like the structure you captured and the color of the galaxies.

I didn't realize it was so dim and required as much exposure. This is on my to do list and I can barely reach this from my location. It may take too many nights at a dark site to get even close to what you have.

JB

[multiweb]

An old favourite. Incredibly deep and detailed. One for the poolroom. :thumbsup::thumbsup::thumbsup:

[Placidus]

Thanks John. The main body of the two colliding galaxies and the inner parts of the antennae are not so difficult, only the extreme outer ends.



Thanks, Marc! In other news, sticking my head out the window as I type, I can see the pre-eclipse moon peeking between seriously heavy clouds. Not long to go.

[AlexSavoy]

Truly look amazing. Beautiful colors and amazing quality. Work of art :)

[cometcatcher]

That's an awesome shot! I had fun imaging this a while back with the 8". (Through your finderscope ;) )

[strongmanmike]

Ok Kevin...how many peoples finderscopes have you stollen..?? :shrug: :lol:

Mike

[cometcatcher]

;) This is going to sound dumb, but I would love to try my K-5 on that 20".

[Bassnut]

I imaged this and found the antennae really hard to bring out, required masking out and seperate super stretching. Im guessing you didnt go that far, so this result is very pleasing indeed guys, well done!

[Placidus]

Thanks, Fred.

Grasshopper say: Easy question needs complicated answer. We used a mask, but one generated mathematically, not painted on by hand, whose only goal was to protect the galaxy core, not to "mask in" the antennae, which would be cheating. We produced two versions of the final image:

A: very strongly stretched after strong wavelet noise reduction, to show the antennae.

B: Deconvolved but with very little stretch, to optimally show the galaxies.

We then produced a mask M by low-pass filtering (blurring) image B with a filter constant of about 100 pixels. The final image was image A where the mask was dark, image B where the mask was bright, and pro-rata in between. The mask generation process did not involve optimizing the appearance of the antennae. That was just lots of exposure time.

Distinctly dodgy would be for example use PhotoShop to manually paint a mask on where you think the antennae should be, or where you think the galaxies should be. That way you just get what you were hoping to find, rather than what's actually there.

Legitimate is to adjust the black and white points on the mask, because that, plus the filter constant, are just 3 degrees of freedom, know nothing about the presumed shape of the antennae, and is unlikely to produce a pair of antennae out of nothing.

Hope that incomprehensible rave helps.

Best,
Mike