Centaurus A Extreme Deep Field - 120 Hours

[SkyViking]

Hi All,

Over the past few months I have been on a mission to achieve a long time dream of mine: Taking a deep sky image with more than 100 hours of exposure!
Now, after having gathered 120 hours of data over 43 different nights in Feb-May 2013, I'm happy to present what appears to be the deepest view ever obtained of Centaurus A (sorry Mr. Sidonio :P). This is likely also the deepest image ever taken with amateur equipment (faintest stars are magnitude 25.45).
I spent around 40 hours processing and analysing the data, with the goal of presenting this majestic Southern galaxy as it has never been seen before - with all the main features showing in one single image, in order to truly get a grasp of what this intriguing object is all about.

Link to full gallery (http://www.rolfolsenastrophotography.com/Astrophotography/Centaurus-A-Extreme-Deep-Field)

Link to high resolution image (~4MB) (http://www.rolfolsenastrophotography.com/Astrophotography/Centaurus-A-Extreme-Deep-Field/29643205_8ZwvgW#!i=2536914799&k=mNgSprP&lb=1&s=O)
Link to high resolution image with 709 globular clusters marked (~4MB) (http://www.rolfolsenastrophotography.com/Astrophotography/Centaurus-A-Extreme-Deep-Field/29643205_8ZwvgW#!i=2536914391&k=vSwmngT&lb=1&s=X3)
Link to comparison of jet details with a 50 hour image from ESO’s La Silla Observatory (400kB) (http://www.rolfolsenastrophotography.com/Astrophotography/Centaurus-A-Extreme-Deep-Field/29643205_8ZwvgW#!i=2536913562&k=BZsTXtD&lb=1&s=X2).
Link to image of detailed magnitude readings (400kB) (http://www.rolfolsenastrophotography.com/Astrophotography/Centaurus-A-Extreme-Deep-Field/29643205_8ZwvgW#!i=2536913587&k=jWT5V4T&lb=1&s=X3)
Link to gallery of distant background galaxies in this image (200kB) (http://www.rolfolsenastrophotography.com/Astrophotography/Centaurus-A-Extreme-Deep-Field/29643205_8ZwvgW#!i=2537067292&k=pZmrPXs&lb=1&s=O)


Visible are some unique features, some of which have never been imaged before by amateurs:

A set of enormous reddish filaments associated with the relativistic jets.
The complete shell structure of the extended halo, showing both the faint outer shells and brighter inner ones.
709 of the catalogued globular clusters orbiting the galaxy.
Integrated Flux Nebulae permeating the entire field of view around the galaxy.


Image details:
Date: Taken over 43 nights in Feb-May 2013
Exposure: LRGB: 90h:10h:10h:10h, total <b>120 hours</b> @ -28C
Telescope: 10" Serrurier Truss Newtonian f/5
Camera: QSI 683wsg with Lodestar guider
Filters: Astrodon LRGB E-Series Gen 2
Taken from my observatory in Auckland, New Zealand

Some Notes about Image Processing
This extremely large set of data was truly a pleasure to work with. I am now, more than ever, convinced that one can never have too much integration time.
Even though the surrounding Integrated Flux Nebulae and shell structure of the faint outer halo of the galaxy is plainly visible, no noise reduction was applied to the image at all. Another thing that greatly helped with the processing was that I chose to do the majority of the work in PixInsight 1.8. I had for years been using the old demo version, PixInsight LE, mainly for its powerful gradient removal feature (DBE), but I must say that switching to the full suite of PixInsight tools has really taken my image processing to a new level.
I look forward to continue learning and improving my techniques with this great piece of software.

Shell Structure of the Halo
The entire halo of Centaurus A is seen here as consisting of concentric shells which are remnants of past mergers with other galaxies. The formation of such shells are a common observation in computer simulations of merging galaxies (http://vimeo.com/32271838#).
The shells form when the cores of merging galaxies orbit around their common centre of mass in an ever tighter orbit while disrupting the halos of both galaxies and sending billions of stars into eccentric orbits. This process creates outward travelling density waves until the collision eventually settles as one single larger galaxy.

Jets, Lobes and Filaments
Centaurus A is the closest radio galaxy to us and is hosting an Active Galactic Nuleus (AGN) (http://en.wikipedia.org/wiki/Active_galactic_nucleus) in its centre. It is believed that the twisting of magnetic fields in the accretion disk around the central supermassive black hole collimates the outflow along its rotation axis, so a resulting jet of plasma emerges from each face of the accretion disk.
These jets emit strong synchrotron radiation which is ultimately detected on Earth as radio waves (Centaurus A is one of the strongest radio sources in the sky). Two large lobes on opposite sides of the galaxy are the main feature in radio images (http://www.mpe.mpg.de/~hcs/Cen-A/Pictures/atca2009.jpg).
A set of apparent huge reddish filaments associated with the jets are visible in this image. Details include a bright inner filament about 30,000 light years from the core and another larger filament some 65,000 light years out. Both of these extend from the core towards the lower right in the 4 o'clock position. A corresponding faint trace of nebulosity, likely related to the otherwise invisible Southern jet, is also noticeable as a small red smudge on the opposite side of the galaxy core, in the 10 o'clock position about halfway between the core and the upper left corner
This illustrates the effects of Relativistic Beaming (http://en.wikipedia.org/wiki/Relativistic_beaming), where the jet that is pointed more towards us appear much brighter than the opposite facing jet. This is a common feature of active galaxies with jets and the same effect can be seen in for example the giant elliptical galaxy Messier 87 (http://www.rolfolsenastrophotography.com/Astrophotography/Exotic-Objects/25329666_z2DJLB#!i=2082561863&k=83wM38r&lb=1&s=O).
Interestingly, shock fronts in the outer portion of the bottom facing jet seem to also have triggered a burst of star formation in the surrounding gas, visible as a prominent sprinkling of faint blue stars scattered around the left of the outer lobe.

The Deepest Astrophoto Ever Taken with Amateur Equipment?
The FITS file was astrometrically solved and magnitudes calibrated against a white star (USNO-B1.0 0470-0346877). Subsequent magnitude readings from Maxim using aperture photometry show plenty of stars below magnitude 25 with the faintest recorded at magnitude 25.45. Specifically magnitudes of 25.03, 25.12, 25.22, 25.42 and 25.45 were read from point sources just in a small area around RA 13 26 54 Dec. -42 50 45.
The results seem to confirm that this Extreme Deep Field image surpasses the previous record made by Ken Crawford and Johannes Schedler's 2007 image of quasar CFHQSJ1641+3755 (http://panther-observatory.com/gallery/deepsky/doc/CFHQS_J1641_f10.htm) (Mag 24.80), and also the 2011 deep image of quasar QSOJ1148+5251 by Christian Sasse (http://www.global-rent-a-scope.com/gras-news/2011/2/8/imaging-the-edge-of-everything.html).

Globular Cluster Population of Centaurus A
According to the SIMBAD database there exist 883 catalogued globular clusters in the halo of Centaurus A, as of 2013. The first 80 globulars were found in the 1980's, and the rest has only been discovered recently in 2004 and later years. It is believed that these globulars only represent about half the total population and a further 833 new globular candidates (http://iopscience.iop.org/1538-3881/143/4/84/fulltext/aj_143_4_84.text.html) were identified in 2011.
In this extremely deep image I have been able to identify 709 (87.5%) of the 810 currently catalogued globular clusters that fall within the field of view.

About Centaurus A (NGC 5128)
Centaurus A is a peculiar galaxy located around 11 million light years away in the Southern constellation of Centaurus. It is the closest active galaxy to us and one of the most studied in the sky. The true nature of the galaxy is a matter of scientific debate and its type has been classified as either a lenticular or giant elliptical galaxy.
The prominent dark obscuring dust lane is believed to be the result of a recent merger with a smaller spiral galaxy. This collision also likely triggered the intense star burst activity resulting in the distinct blue glow from bright young stars around the area of the dust lane.

I have attached a few images here, but the high resolution version linked above is worth having a swim around in ;)
Have fun, comments and critique welcome as usual.

Regards,
Rolf

[Octane]

OMFG.

:prey2: :prey2: :prey2:

No words. I'm just gobsmacked by the mammoth undertaking, but, moreso by the incredible final result in all its magnitude (pun intended!).

H

[Octane]

Rolf,

I will be in Auckland this weekend for some beauty/fashion photography. Want to meet up on Saturday evening? Only thing is that I will be without transport. :(

H

[DJT]

Stunning image!:eyepop:

[RickS]

Truly fantastic, Rolf!

[johnnyt123]

marvellous absolutely incredible.

What a Goliath undertaking. Well done

[icytailmark]

wow 120 hours for just 1 image thats incredible work. How do you find the patience and time?Just out of curosity how many Gigs of data did you capture in total? This deserves to be image of the year.

[LewisM]

What H said, multiplied by 6E12 :)

[el_draco]

Ouch!
:eyepop:

[rustigsmed]

Wow wow wow!
Awesome stuff, congratulations on the result Rolf, that is a lot of work and its truly paid off.

that's a lot of hours, how long were the subs? I would imagine your computer would battle digesting the stacking!!

Cheers

Rusty

[gregbradley]

Image of the year. What an incredible effort. Expertly processed. Its all there, the shells, the jet, the dust areas.

Greg.

[TheAstroChannel]

That is incredibly beautiful, Look's like an image that only a machine could capture! Marvelous work!

[Larryp]

Wow! That's superb

[alpal]

Hi Rolf - that's great work - the halo is huge.
It will have scientific value.
You deserve an APOD.

cheers
Allan

[Cosmic]

wow:bowdown: absolutely amazing!! Time well spent, and the results speak for themselves!!!

[clive milne]

Rolf, kudos for the work that went in to this image and the result...
It is truly gratifying to see that you did it with a humble 10" newtonian as well!

One minor point;
The magnitude limit of Christian's deep field image is realistically 27.5 or there abouts, but.... that was done with a deep depletion sensor and IR filters if memory serves me correctly..

However you slice it, you have set a new standard that I hope others will adopt.

respect
~c

[DavidU]

:jawdrop:Oh my gawd.

[Peter Ward]

OK..the dark lanes look like someone put a parking sticker on the galaxy...one does need to "respect the light"

but....... Jaysuswepped !!!

Rolf! Bltized it! :thumbsup:

Sublime outer halo detail. :thumbsup::thumbsup::thumbsup:

The benchmark deep-sky image for 2013 IMHO.

[Phil Hart]

Count me among the impressed.. that's some piece of work for sure! I think it's great to take the attitude/approach of aiming to do one thing well. :thumbsup:

Phil

[Zubenel]

As above :eyepop::thumbsup::):2thumbs::D

[strongmanmike]

Well my friend, I knew the day would come for me to hand over the Centaurus A mantle, I knew some day someone would take the bull by the horns and surpass my effort from May 2008 at Wiruna, and pow you have certainly done that :eyepop:.... frankly I am surprised it took so long...aaaalthough :whistle: in my last vestiges of relevance before being relegated to mediocrity...my field is wider so does show the "full" outer polar extentions of the galaxy :P

I have had a good look at all your presentations of the data and this is a spectacular result Rolf (not to mention out right interesting) and something to be very proud of :thumbsup:

Something I related to was the pleasure you mention when working with that volume of data, I remember with my 20hrs taken from a true dark sky it was indeed easy to play with and gradient and noise reduction were almost non existent...as for having 120hrs at your fingertips...I can only imagine...

120hrs..... :doh: The Germans invented this didn't they blitzkrieg ? and 43 nights :eyepop:.....I'll just go and rock back and forth in the corner dribbling now...

Mike

[sjastro]

Congratulations on a fine image Rolf.

Steven

[E_ri_k]

Speechless:jawdrop: That is absolutely superb:eyepop:
Well done, that's a HUGE effort, and the results speak for themselves.
Erik

[Paul Haese]

Well done Rolf. Detailed and very smooth image. Great colour and contrast. Shells are well shown and I believe show detail never shown in an image by an amateur. Certainly the deepest image of Centaurus A image I have ever seen.

The jet off the lower right is impressive to say the least. I also am impressed by the ha regions showing up so well.

Very nice image. Spectacular.

[h0ughy]

wow - very impressive. I don't have the processing skills to comprehend this monumental achievement but it certainly is a tenacious Herculean effort. Boldly fantastic!!!

[Enrique]

:eyepop::eyepop::eyepop::eyepop::ey epop:

[icytailmark]

this would of taken months to process on a half decent computer.

[astroron]

Fantastic work and a stunning image.
Your skill knows no bounds Rolf :eyepop:
Cheers:thumbsup:

[Shiraz]

simply outstanding work Rolf - thanks for posting it so we could see what this object looks like.

[RobF]

Just amazing Rolf. Tops even YOUR wildest efforts to date.
Bit biblical actually - 40 nights of data, and perhaps 40 days to process it so wonderfully? :)

BTW - if anyone starts criticising new images on IIS because they've got less than 100hrs, its all your fault.....;)

[dvj]

I for one appreciate the excellent capture of the jet deatail compared to the ESO data. :eyepop:

[iceman]

That's quite amazing. Blown away I am!

Wow Rolf, you've outdone yourself. Incredible effort - you're a credit to amateur astrophotographers everywhere.

[troypiggo]

Massive! Such dedication and commitment. Most of us impatiently wrestle with maybe a few hours of data on one target. 43 nights on one target! Your mount must almost know the way by itself after that!

[Peter.M]

I am frantically trying to find a hat around my house so that I can take it off to you Rolf.

Fantastic

[multiweb]

:eyepop: Just saw that one now. Gee that woke me up in a big way . :lol: Don't need a coffee anymore.

Wowwowow!... where do I start. Mind-blowing shot. It's got everything in one rendition. You've managed the colors and the whole dynamic range in a subtle way. As usual the read in so interesting like all your other reports. 120h is a mammoth efforts and the result is fantastic. Also loved all the smaller shots and comparisons to the ESO pics.

I'll echo what everybody else said. You're a credit to the hobby mate. :bowdown:

[Lester]

Outstanding image Rolf, thanks for the view. It poses the question; as to what is the limit of how deep we can go with images. I thought the atmosphere of our planet would cause a limiting factor? All the best and look forward to seeing more of your work.

[jase]

A splendid image Rolf! I admire your dedication in sticking to the plan and the write up on your approach is just as good as the image providing even further insight into your methodology. Its not easy to put a familiar target in a different light, but you've done it with exquisite results.

I do however wonder...90hrs of luminance? Really? Is that how much you acquired and used or did you acquire far more than that and throw away the subs that didn't meet FWHM requirements? I suspect the signal to noise ceiling was well below this, perhaps offering diminishing returns beyond 50hrs. Did you measure this? What however such a large volume of data provides is greater choice. Choice to include only the exceptionally low FWHM subs.

Thoroughly enjoyed the jet and along with the shell extensions as it fades naturally into the galactic cirrus. A minor technicality in the name. This is not Centaurus A, but NGC 5128. Centaurus A is the radio source within NGC 5128, but a rose by any other name would smell as sweet. ...and talking names, 'Aotearoa' or the land of the long white cloud has become a myth. Clearly you do get endless nights of good astronomical weather! Probably rival many places in Oz.

Once again, excellent work. If you produce a solid image each quarter, you should be happy. In this game, its quality over quantity. Well done!

[Ric]

Hi Rolf

That is really something special, great images and a great write-up as well.

Thank you for posting an amazing image.

[Dennis]

Hello, Rolf

Well, you’ve really smashed this one right out of the park…:thumbsup:

No doubt you got bored with Milky Way globulars, so you’ve spread your wings and flown beyond our galaxy to pick up just a few hundred or so elsewhere, in the vast reaches of our cosmos.:)

A most wonderful and inspirational piece of work Rolf, it really lifts the “what’s possible” genre to a whole new level and injects amateur astronomy with inspiration for new horizons.:)

Cheers

Dennis

[scagman]

:jawdrop:As everyone else has said. WOW, very very good. Just awesome.

cheers

[rmuhlack]

What an phenomenal image! A world-class result.

As others have said, you've lifted the bar to what is possible with amateur gear and determination. Inspirational :)

[Poita]

I would love to see some more info on how you go about processing this much data!

[pvelez]

Thats it - I'm packing my gear away and taking up macrame.

Simply awesome Rolf. Magnificent.

Pete

[Bassnut]

Amazing Rolf, well done. And with a 10"!, megadata really is the last mile.

[Joshua Bunn]

Fantastic Rolf, really admire your dedication to this target.

Was it hard to decide from all the objects out there, which one to spend this much time on?

Josh

[gregbradley]

Yes good point. How do you stack say 50 hours of luminance? I take it you did it in batches and then combine the batches? That's what I have to do often if I have a lot of data. CCDStack complains easily about memory usage.

Greg.

[Earl]

Amazing. Been said. But needs saying again!

[Osirisra]

Holly cow!!!:eyepop: :jawdrop:what a jaw dropper of a image! Great write up too:thumbsup:

I bow before you oh mighty master! :bowdown:

Epic, epic, undertaking. How you managed to get 43 nights of data in fours months is totally mind boggling in it's self. Would take me years to clock up 43 good nights! You must have a very special deal with the weather Gods indeed.




...Wow...

[Suzy]

Rolf you're a legend! :scared2:

What talent- I'm still trying to get over the fact that you imaged & plotted a swarm of globular clusters surrounding the Sombrero Galaxy (M104), and also captured a planetary accretion disc around the star beta Pictoris (being the first amateur to do so) which had Phil Plait going crazy for it (http://blogs.discovermagazine.com/badastronomy/2011/11/26/amateur-astronomer-glimpses-an-alien-solar-system/#.UaQuvNjYCSo), now you go and do this!

[colinmlegg]

Love your work Rolf. I want to do what you do when I grow up ;)

[big_dav_2001]

Wow... That's all I can say... Wow..

Congrats on an amazingly beautiful photo

Davin

[stardust steve]

i was wearing socks until i saw this image, then they got knocked clean off.
Fantastic image:thumbsup:

[MrB]

Ever had an APOD before? You will soon.
Absolutely stunning work!

[g__day]

Can only imagine the planning, perseverance and effort this took to carefully collect the data. How long did the processing take? Awesome result!

[David Fitz-Henr]

A monumental image Rolf! I've never seen such a deep shot of NGC 5128; fantastic work! Very well done indeed :thumbsup::thumbsup:

[Leonardo70]

Congrats Rolf ... :eyepop:

This is passion.

All the best,
Leo

[PRejto]

You Sir are the Jascha Heifetz of the amateur astronomy world. Bravissimo. Incredible. Words fail, but thank you!

Peter

[coldlegs]

Utterly Magnificent Rolf!

Cheers
Stephen

[ZeroID]

<Speechless, just speechless>

[Irish stargazer]

:jawdrop:

[Ross G]

A unique and beautiful photo Rolf.

What an amazing project.

You are an inspiration.

Ross.

[marc4darkskies]

:jawdrop:
To say that I'm impressed is an understatement Rolf! What a tremendous effort for a spectacular result. Without equal IMO! :eyepop:

Cheers, Marcus

[pixelsaurus]

Well done that man!

[SkyViking]

Thank you everyone for your kind comments and overwhelming response, it is all very engouraging (and I'd need some serious encouragement to top this exposure time! :lol:)

To answer a couple of the questions that were raised:


Thank you Mark, it wasn't really too bad because I have a permanent setup and can just flick the switch so to speak. I let the scope collect all it could on every clear night while the galaxy was visible from my location. I started out when it was rising around midnight, and over the months the imaging obviously shifted earlier and earlier. On these 43 nights I was able to take many other images on the side, either before Centaurus A was in a favorable altitude, or after it had passed out of my view. For example I did all my NIR work (http://www.iceinspace.com.au/forum/showthread.php?t=106805)while grinding away on this project, so I didn't grow too impatient. :) I still have a lot of data for a few other targets captured during this time that I just haven't had time to process yet.
In terms of raw FITS files I got around 45GB of them. And all up my Centaurus A folder is currently siting at 75GB, but that includes everything such as batch stacked files (more on that below).


Thank you Rusty - I use 300s sub frames for luminance, and 380s, 280s, 280s for R,G,B respectively. I have experimented and found that this gives me the optimal S/N ratio for my combination of average sky conditions and telescope/camera.
I had to do the stacking in batches for two reasons: Firstly, I found that in Maxim the plain old Average combine method actually produce the smoothest result, quite a lot better than any of the the other fancy stacking options. But that meant I had to weed out the bad frames by hand... Secondly, since I had around 1500 frames there was just no way it would stack them in one go without throwing errors (and it would take hours probably). So I manually stacked them all in batches of 10, and then stacked those together for the final FITS. Fortunately I could do the batching little by little as I gathered more frames each night.


Thanks Peter, I just knew you would comment on the dust lane :lol::D
I actually did consider this quite a bit but decided that the dust lane is the defining feature of this galaxy and that it should therefore feature prominently in the image. My goal was to create an image that showed all the main features at their best, as such an image has never been made before of this target. So while I may not have 'respected the light' (am I one of those now:eyepop::lol:) I did so contiously based on my subjective preferences. ;)


Thank you very much Mike, I'm glad to see you take it like a gentleman :lol::P.
Out of respect for your efforts I actually had my reservations about going this deep on Centaurus A in particular, but given the season and visibility from my location this is actually one of the targets that I get the most observing time on over the year. So for that reason, in order to collect as much exposure as possible, it was an easy choice.
I also simply find it an extremely interesting galaxy with so much stuff to show both in the bright and faint regions, so a good target all up for this kind of image.
Actually I do link to your great image from my site (if you don't mind?) for the very reason you point out. Let's face it, I didn't quite fancy doing a 3 x 120 hour mosaic to include the outer polar extentions of the halo... :eyepop::lol:
Thanks for your comments Mike, your image has certainly been an inspiration for me.:thumbsup:


Thanks yeah yes the mount almost did know its way!
I still home in on my targets the old fashioned way, by star hopping. I must admit that in the end it took me only literally a few seconds to get Centaurus A lined up and centered on the chip - and that often done during twilight when all I had to go by in the finderscope were nearby Omega Centauri and a few lonely stars.


Thanks very much Jase, yes I did collect more data than the 'mere' 120 hours included here. Somewhere around 127 hours all up if I remember correctly. So I certainly lost some frames to poor guiding, reflections, bright satellite trails etc. It was a pitty having to throw away 7 hours, but overall that is still a pretty good success rate. I usually get to use almost all my data.
I thought about doing a separate stack of only the best frames to achieve maximum detail just in the dust lane. After around 40 hours of processing etc. I didn't get around to it. But maybe some day, perhaps a Sidonio is coming up... :)

Regarding the weather, we certainly do get plenty of clear nights over here. It is not uncommon that the clouds will disappear at night so the conditions are quite favorable. But still probably nothing compared to the interior of Australia I imagine!




Thank you Dennis, yeah it's pretty crazy with the extragalactic globulars. My tally is now on 709, plus 135 in the Sombrero and a handful in Atoms for Piece Galaxy, so all up ~850 in total... Shall we say first to a thousand? :lol:


Thank you Josh, see my reply to Mike above. This is one of the galaxies that I get the most observing time of, so it was an obvious contender.


Thanks again everyone, it is always great to share ones results with such a great bunch of astronomy aficionados! :thumbsup::thumbsup:

Regards,
Rolf

[SkyViking]

Thank you for your comments Clive :)
I have been studying Christian's image quite a bit and I just want to add some notes about faint magnitudes:

If we want to know how faint we can see we must be careful with what is actually measured. One obvious problem is that to obtain the deepest views possible we use the luminosity frame, where all the signal has been picked up, as opposed to the RGB frames where only a portion of the spectrum is recorded. However, official catalogues give magnitudes as seen though specific filters B, V, R etc.
So what I did in my own image was to calibrate the FITS against a white star (within 0.1 magnitude difference in the three bands B/V/R). After having done this it is then possible to measure other stars and read a magnitude for them. But all that this tells us is really just the white light magnitude of the given star. It may have a much fainter magnitude in a particular colour band, which is often the case, but I don't think that can be fairly reported as the faintest magnitude in an image.

While Christian's quasar image is certainly a magnificent effort, and indeed does show the most distant object ever captured by amateurs, I cannot quite get the supposed record magnitudes to add up with what the image is showing.
And I think this point is essential in order to establish how faint we really are able to see in these long exposures.
This is not to say that the reported magnitudes in the qasar image are incorrect, but merely that they may not exactly represent what we are looking for when talking about the faintest stuff that we can see.

If we look at the magnitudes reported in the image here:
http://www.itelescope.net/display/ShowImage?imageUrl=/storage/post-images/J11485251%20Sasse%20quasar.jpg?__SQ UARESPACE_CACHEVERSION=133672449388 1
To the left of the quasar is a normal star, labelled magnitude 23.1 and the quasar itself is m23.3 in IR. Notice how there is an enormous difference in signal even though these two supposedly have almost the same magnitude. This is because the quasar light is redshifted out of the spectrum so that only a small portion reaches the sensor, where on the other hand the star emits light across the entire spectrum that the chip is sensitive to. As Christian points out: "Its redshift is so large that it has no 'visible' magnitude as such!" So a lot more signal is picked up from the star than from the quasar, although they may both have roughly the same magnitude in the IR band.

Similarly, there is a supposed magnitude 26.9 source immediately to the right of the quasar, but judging from the image this one seems to be of nearly equal signal strength to the quasar itself, although there are supposedly over three magnitudes of difference between them. Again this can be explained easily if these magnitudes are in fact given for particular bands.
I don't know if the 26.9 magnitude comes from a catalogue (and if so, which band is it?), but if not then another potential issue is that this source is so close to surrounding sources that it cannot be reliably measured by aperture photometry. This method would in fact give an inaccurate reading that would be much too faint. This is because aperture photometry relies on comparing the signal strength on a point source with that of the surrounding background (there has to be enough un-obscured background around it). But the background in this case is heavily influenced by the bright sources that nearly touches the supposed magnitude 26.9 source, and as a result the S/N ratio between the source and the background would be measured much lower than it really is - and thus leading to a much too faint magnitude reading.
Aperture photometry can only reliably be used for point sources that lie away from others. In my image I have only measured those stars for which Maxim aperture photometry was not impacted by surrounding sources. There were actually plenty of even fainter readings when I analysed the FITS file, but I did not report these as actual magnitudes because I think they were not reliable (S/N very low and magnitudes fluctuating wildly just by moving the aperture from pixel to pixel, which indicate the measure is unreliable)

As outlined, there is just not enough information to establish how Christian arrived at these numbers so the above are just my observations and comments based on my own experience in determining limiting magnitudes.

As a result of this, I do genuinely believe this 120 hour image of Centaurus A is the deepest image ever recorded with amateur equipment, but I'm certainly open for all scrutiny and more than happy to stand corrected if this is not the case.

[Osirisra]

Congrats on The Universe Today article, I expect to see this awesome image in magazines and website all over the place, APOD next :)

[alpal]

Yes it's here:

http://www.universetoday.com/102473/an-amazing-deep-field-view-of-centaurus-a/#more-102473

And yes - it just has to be an APOD.

[DavidNg]

Wow..

[John Hothersall]

I am out of words, a great thread to read. 120hours would take me 2 years. Great achievement which encourages everyone as the potential for moderate sized scopes has just increased dramatically.

Admiration, John.

[Greg Bock]

whoa,...fall off your chair stuff that Rolf, that halo is so extensive. Congrats on the APOD too, well deserved.

[alpal]

No APOD yet!

[Jeffkop]

I cant imagine trying to process all that .. its a head ache with 10 hrs of data trying to align subs of the same type then align them all .. painful hours of trying to eliminate hot pixels cold pixels column defects .. as someone else aptly put it ... shaysus .. WOW .. you must have a camera that has little or no defects and low noise .. An award winning result mate .. up there with the best astro photos Ive seen .. You would have to be ... well .. over the moon

[gregbradley]

This image should spark a thread about signal to noise ratio and how much gain extra exposure time will provide.

As I understand it the signal to noise ratio improves to the square root of the increased exposure time. So it must take a LOT more hours to get that last little bit.

Did you find that Rolf with this image? Or did you wait until you had the full 120 hours to process it. I wonder what it looked like at say 40 hours for example.

Greg.

[naskies]

Whoa! Beyond amazing... you've outdone yourself again, Rolf! :) I really enjoyed your write-up too. Many thanks for sharing!

[seeker372011]

This image has a momentous air about it..like climbing Mt Everest ..as a country man of yours did some 60 years ago...or breaking the four minute mile or something of that ilk

But beside all that just simply enjoyed the image

Thank you

I do hope it is adequately recognised by being selected for an APOD or whatever. I have no doubt we'll all be reading about it in a future issue of Sky and Tel or Astronomy and seeing the actual image in a double spread in one of those

[Stevec35]

Another incredible result Rolf! Congratulations!

Steve

[alexch]

Rolf,
I only saw your image now and WOW! What an effort and the result has left me speechless for a while. I'll be coming back to look at it again and again.

Thanks for the view!

Alex

[LucasB]

That is incredible. Super deep and fantastic processing! :thumbsup:
Lucas

[Forgey]

Fantastic work Rolf, absolutely stunning!

[AG Hybrid]

Very impressive work.

[Ken Crawford]

This is truely ground breaking showing that the returns in exposure time really do pay off - and the limits may be farther than one thnks. Congrats on not only a great effort - but great result!

[atalas]

Looks excellent! well done.

[ssgrasso]

Simply amazing! Well done, all the hard work certainly paid off!
-Sal

[irwjager]

Congratulations on this magnificent result Rolf. Your repeated pushing of the boundaries of what's possible (or thought was possible, only to show us otherwise) should be an inspiration to us all. I can wholeheartedly tell you that it is for me. Well done.

[Oleg]

Very beautiful, can't imagine how much time you've spent in total!

[MrB]

Was just looking at the images again and to my untrained eye, there looks to have been some changes out there?

[Bassnut]

Damn, and you made the OTA :eyepop::eyepop::eek::thumbsup:

You casually forgot to mention that little gem.

http://www.rolfolsenastrophotography.com/Category/Serrurier-truss-newtonian/25456460_CHP5wT#!i=2096667426&k=jjSGnfG

[Rod771]

Congratulations Rolf :thumbsup:

What an amazing image.

Well done

[Gem]

On those night when I try to work out if I should have 10 or 15 or 20 images to stack ... I might have to increase that number now!!
Well done!!!!!!!!!!

[marco]

Congratutalion Rolf for the commitment put to obtain this record breaking image! I am used to very long exposures, however I doubt I will ever collect so much light on a single object, perhaps now that you cast the challenge I could think about it ;)

Thanks for posting this jaw dropping result

Clear skies
Marco

[FranckiM06]

:eyepop:Wow what stunning image. Pffffuuu, it is incredible to see soo much details in there. Congratulations about your work and the processing
Franck

[JohnH]

:2thumbs:There are insufficient superlatives to describe what you have done. Magnificent.

[broca]

This is APOD worthy! I am floored by so many things in this image. The image itself is breathtaking, the fact that this is imaged through a scope Rolf built himself and that it rides on a G11! Well done all around. Move over Gendler ;)!

[SkyViking]

Thanks again to each and everyone for your engouraging comments! :)
Now I have to figure out where to point the scope next, but so far it's been cloudy here.


Yes Greg absolutely, I did a couple of stacks along the way so I could see the difference. From the last 50-60 hours I gained about 1 magnitude, from ~24.5 to ~25.5 :P
But this also markedly descreased the background noise and made processing far easier. I couldn't have brought out the excruciatingly faint outer details to this degree with say half the integration time, so it was worth it.


Thanks for spotting this, I think I know what happened. In the ESO field there is a very very faint star right at the tip of the bend in that filament, which seems to have been poorly handled during my processing so it now looks sort of like an extension of the filament...:doh:I hope to get around to fixing that soon :)


Thank you Fred, I'm actually in the process of building a larger 12.5" version so I can get to go really deep :lol:

[davenn]

outstanding work with your imaging, Rolf, very well done

looking forward to more gems from you :)

Dave

[DannyV]

Wow well done Rolfe - it's beautiful - and instructive, it's a study to show us how far we've got to go!

Thanks for the link in the IceInSpace news folks, I would have missed it otherwise.

[DavidU]

I can only imagine what you could do with that:eyepop:

[Lee]

Excellent work Rolf....

Have you any pearls to share with other G-11 owners?? Have you made any mods/adjustments to the mount?

[andyc]

Just adding mine to the long list of positive comments - this is a truly staggering image, really pushing what (very few) amateurs can do these days, and totally unthinkable a decade or two ago. I'm very very impressed. Wow! :bowdown:

[SkyViking]

Thank you Dave, glad you enjoyed it!


Thanks Danny, I do try to write up some detailed info on each subject that I image, naturally this one deseved a bit of extra details. I'm glad you found it useful :)


Thank you David, Mr. Royce just last week notified me that he has started grinding my mirror, so hopefully it's not too far off now :D


Thank you Lee :) Actually I have no tips whatsoever because my mount is unmodded (and probably even a bit neglected :eyepop:). I re-greased it a while back but I think it's time to do it again, just haven't gotten around to it yet... If I was to improve it I would invest in a set of upgraded worms - I think that's the only issue I have with it. My tracking definitely shows larger movement in RA than in Dec so it's not ideal.


Thank you very much Andy, I appreciate it :)

[lazjen]

This is not only a great image, but the write up detail is excellent reading as well.

Impressive work. :thumbsup:

[Galaxygazer]

Hi Rolf,

This is not only an AMAZING piece of work, it is also a beautiful piece of Science and Art. Well done!

Just a word of caution when talking about the faintest object - this is really difficult to assess as the word "faint" has to be associated with a well calibrated magnitude. Paul Boltwood, Ken Crawford and myself have done imaging of 10 hours and more, I hold the record for the most distant quasar imaged with an amateur telescope. When I declared a 27 magnitude galaxy I was cautioned by a professional astronomer due to above mentioned reason, and he is right. So the word "faintest" is a very difficult term.

I really applaud your effort and great result.

Christian Sasse

[Elio]

As above, again...:eyepop:

:thanx:

[SkyViking]

Thanks very much Chris! :)


Thank you Christian, your quasar image has certainly been one of my inspirations to push the boundaries. Yes as I mentioned in some of the earlier comments, it's very difficult to establish what is the 'faintest'. It all depends on reference catalogue data and filters etc, as you say it really cones down to proper calibration. And then there are also things like faint IFN glow and galaxy shells etc. which have exteremely low surface brightness, all of it still visible in our images but having surface magnitudes way below that of the point sources - I'm not sure how to best measure that.
It's truly fascinating to think how deep and far we as amateurs can reach out into the Universe!


Thank you Elio! :)