The Antennae from ARO

[ericwbenson]

Hi Everybody,

Well I have been tweaking this on and off for quite a while (~ a year !?!), maybe time for some outside feedback. Attached is a 4x downsampled center crop version of my image of NGC 4038/39 aka Arp 244 or The Antennae galaxy taken from the Arkaroola Remote Observatory with a 20" CDK and 18.5 hrs of data.

The original data was contaminated by rainbows and flares. These were caused by off-axis starlight reflecting/dispersing off the corrector lens cell inside walls. Anodized aluminum seems to act as a dispersion grating when struck at very shallow angles as I found out! After major flat-field surgery most of the artifacts were subdued although it limited the amount of stretch I could really apply.

Please follow links for image acquisition details and half (http://www.faintgalaxy.com/ngc4038.htm) and full (http://www.faintgalaxy.com/ngc4038_full.htm) resolution images.

You can compare this image to other Arp objects I have imaged, mostly with a C11 and a few with a C14, here (http://www.faintgalaxy.com/astrophotos.htm). I think the larger corrected field of the CDK is evident when compared to the SCT...

Cheers,
EB

[Peter.M]

Wow that is an amazing image, even more amazing is how much noise is still in the background after 18 hours of exposure! Shows how dim those little trails are.

[barx1963]

That is awesome Eric!!:eyepop:
Look at all those background galaxies

Malcolm

[Joshua Bunn]

Very nice Eric, Some great resolution there under those skies and that scope. Is this a remote setup?

[johnnyt123]

This is an amazing pic.

I love seeing the hundreds of galaxies in the distant background.!!!

Suddenly I feel so small......

Great job though...

[alexandre]

Hello !
Super , for me it's a very very nice image !!!

Great image !;)
@lex

[ourkind]

Beautiful and as mentioned above loving all those background galaxies, I just get lost in this image. Thanks for sharing!

[Larryp]

Great image, Eric!

[Deeno]

What a lovely image.
And one of my favorite objects to observe...

[lacad01]

Beautiful image, nice one :thumbsup:

[E_ri_k]

Really beautiful image :eyepop: Well done!
Erik

[Peter Ward]

A few minor quibbles with instrument artifacts and noise, but this is a superb result.....one of the best amateur images I've seen of this object.

Most excellent :thumbsup::thumbsup:

[RB]

What a wonderful image Eric!
Beautiful work.

[marc4darkskies]

Superb Eric! :thumbsup::thumbsup:

Cheers, Marcus

[iceman]

Ditto to the above! Brilliant.

[allan gould]

Great image and very well processed!

[multiweb]

Monster scope and great result. :thumbsup: I'm surprised a PME carries that weight. That's about 70kg right?

[David Fitz-Henr]

Terrific image Eric! All those tiny background galaxies really add to the overall efect!

[stardust steve]

Fantastic:eyepop:
I would love to make a camp trip up that way soon.:thumbsup:

[alpal]

Such a beautiful picture.
It would be great if you could modify that corrector.

[strongmanmike]

Having spent some considerable time processing this pair recently I can say it is a beauty to work with and your version looks amazingly detailed. At the full size though the decon/sharpening ringing is a bit off putting but shrunk to 50% it looks excellent :thumbsup:... a 20" in a high steady dry site like that is very powerful, really look forward to seeing more :thumbsup:

Mike

[Paul Haese]

Eric,

firstly nice to see an image from ARO. Love the detail in the full version, very cool. Colouring looks good too. Love the background galaxy with a tail nearby too.

Yes there is some noise but this could be smoothed out a little using smoothing. There are some dark rings around some of the stars, so maybe address those. Other than that all is good.

Those flares can be a pain for sure.

Please keep the images coming.

[clive milne]

Phwoar...! :applause:

[RobF]

Stunning. Thanks for sharing. Love checking out the galaxies in the full res version. Space is BIG! Really, really Big! :)

[gregbradley]

Wonderful first light for such a large scope. It shows tremendous detail including stars and nebula in one of the sweeping arms I haven't seen before. Decon as mentioned is bit too harsh and a bit too much background noise easily fixed but really minor pickings.

Planewave did bring out a set of baffles you can install on the corrector. I installed them on mine. Reflections arcs, streams of light from bright out of frame stars are definitely the weaknesses of the CDK scope. Mine has improved somewhat but I did get an annoying arc in some otherwise lovely galaxy subs recently.

I also got a revised secondary shroud some time ago which also helped with these.

I have also read that the carbon fibre struts can reflect and reports covering them with flock can help (at the expense of the occasional dropped fibre on the mirror.

I suspect the scope's performance could be improved by flocking the inside of the tubes, the struts,installing the baffles if its an earlier model and making sure you have the latest secondary shroud.

Otherwise its a great scope and in mine the reflection issues only happen occassionally. Whereas with my AP140 refractor it never does. One of the joys of refractor imaging is it can be a whole lot simpler.

Greg.

[ericwbenson]

Yes, it is accessed over a satellite connection and powered by solar panels with battery bank.



That's right, the scope is 140 lbs and the image train comes in easily at over 10 lbs, and I ditched the versaplate, the PW saddle is bolted straight onto the PME dec head, making the scope another inch closer to the RA balance point, even so I'm really at the PME's limit. In fact the tracking is iffy enough that I am upgrading the mount in the very near future.



I was a bit suspicious that the baffles would fully clean up the arcs after my experiments, but I'm very happy with the flocking, it wasn't that hard to do (Mark and I performed the operation on site at night). And yes I did put flocking on the carbon fiber trusses too, since I had caught the odd weird reflection off them (which looked different than the lens cell artifacts). Otherwise the inside of the scope was dark enough and the secondary baffle was only a problem on the 17" AFAIK. Now when I point right next to <1st mag star I can't even tell it's there!



Some have noted the somewhat noisy appearance and decon artifacts in the image. Yes I have struggled with them too, one day they distract me the next not so much. A few comments though:
1) When smoothing the background and very low light features, very often the small faint galaxies get wiped out or smudged very badly at the least. (See the very remote "fish" galaxy bottom middle, and the interacting pair just to the left of Arp244 where one spiral is strung out into a j shape)
So I tend to go very easy on this at the expense of noise. I'd rather attack with more data (which works under Ark's dark skies)...and I agree this image could have used easily another 3-6 hours of luminance. But as the frames were coming down and the artifacts were piling up I was getting a bit frustrated and was going to can the whole series.

2) Gibb's rings (decon artifact): I wish I could control these better, they are often the limited factor to how much one can sharpen. I knew I was on the edge for this one, especially at 100% zoom. But they don't show on a print and the tiny brown dust lanes come out so well with decon...ah well next time.

Note I only used MaxIm for processing (and CCDSharp for LR decon), no selective masks or photoshop tools, which limits me in the kind of adjustments I can do, but I'm ok with that.

3) Flats were not that great. They showed a ying/yang pattern when flipping east-west, and were not always repeatable. A real bear when trying to tease out faint details (see the magenta blotch near the streamer intersection), in fact some good friends of mine remarked long ago that the ultimate "depth" limit of an image was usually the flat quality. The S&T deep field challenge years back was won because of better flats. Never skimp on flats!
During the flocking trip I also adjusted the centering of the secondary mirror, flats are now better, but not perfect. If I make the flats perfectly symmetric the spider vanes are slightly askew and I get wider diffraction spikes...so compromise again.

Does anybody think the image is too blue? I was sorta prepared for an onslaught of: it's way too blue!!! ;)

Thanks all for the comments.

Best Wishes,
EB

[Suzy]

Hi Eric,
I fell in love with your image as soon as I saw it, so I popped it on the IIS fb page yesterday. It did pretty well too, so far getting 70 Likes and 15 shares.
Gorgeous image! :)

[RobF]

Eric, there is no presumption of course, but I suspect many would love to have a play with your data for this image or another if you even decided to make it available. Really is a dream very few here are likely to indulge in. Might be educational for yourself too though.

(Bert has us spoiled of course :) )

[strongmanmike]

All makes perfect sense, it is just good to soak up the cool bits that the processor, scope and site have worked together to reveal, without worrying about the rather minor "imperfections"(?) ...and this image is really quite revealing :thumbsup:

Again, great shot

Mike

[gregbradley]

Hi Eric,

So you flocked the scope since this image? Did it improve it much? I have to do that to mine.

Greg.

[ericwbenson]

Hi Greg,
I think this shows the difference:
Attached color image is the fully calibrated LRGB composite I started with for the Arp 244 image (no flocking). The rainbow is caused by an 5.3 mag star (SAO 157042) 50' away from the galaxies. Subs here were 15 minutes each.
Attached mono image is after the flocking: Altair (mag 0.76) is right on the edge of the chip, ~18' off axis, 60 sec exposure, bias and dark calibrated, stretched using high setting in Maxim.

I've attempted to adjust the stretch to be about the same for similar brightness stars, I think.

EB

[AG Hybrid]

That picture is brilliant! There are galaxies everywhere. Towards the top of the picture you can make out a galaxy cluster with ease.

[gregbradley]

Gee that is a massive difference. Mine is nothing like that. Its the occasional reflection arc which is still annoying.

Thanks for posting that. I'll buy some flocking material and install it.

Did you flock the secondary shroud? I did that with my first secondary shroud and it reduces the secondary mirror aperture a tad and I noticed a slight but noticeable drop in contrast.

The revised secondary shroud has a tapered edge that goes from about 1mm thick at the outer edge to about 4-5mm thick where it meets the mirror and is angled so it does not seem to obstruct hardly at all. It worked well and does not seem to reduce contrast.
Greg.

[Ross G]

An amzing photo Eric.


Ross.

[ericwbenson]

No I didn't modify the secondary housing.
EB