NGC 3621 - delicate low surface brightness galaxy in Hydra

[strongmanmike]

At 12' X 5' NGC 3621 in Hydra is a modest size SBcd spiral galaxy with very faint outer arms. It is about half the angular size of NGC 6744 in Pavo and at 22.3 mag/squ arc sec, has almost as low surface brightness, so it is a challenge to image well.

There are many background galaxies visible but the largest (still well under one arc min in size) and just above NGC 3621 in this framing, is the prominent 16th magnitude face on Sab spiral galaxy PGC 34490

Half the luminance was taken under reasonably good seeing conditions the other half under fairly average seeing and as usual no darks, no flats etc :thumbsup:

Capture details under image:

NGC 3621 Full Frame (http://www.pbase.com/strongmanmike2002/image/154609197/original)

Traditional deep comparison with UK Schmidt :P HERE (http://www.pbase.com/strongmanmike2002/image/154712781/original)

Mike

[Screwdriverone]

Nice one Mike,

That is a lovely one to go Galaxy deep diving on, I think I got up to about a count of 10-11 before I realised I was nose to the monitor and had been sitting there for 5 mins having a surf.

Are the stars in the galaxy a bit pink? It seems slightly mauve/pink around the arms and I am not sure if these are simply the active regions or a colour balance thing?

My favourite fuzzy is definitely the elongated S just above and to the right of PGC 34490.

Love your work. Especially with no flats, darks or bias nonsense. :D

Cheers

Chris

[strongmanmike]

He he Cheers Chris :thumbsup:

Yeah, I like that little S galaxy too, just think, probably has a few billion stars in it :)

Re the stars..? not sure, I can' see the pink stars on my monitor :shrug:..?..the HII regions along the arms and in the core are quite fine and star like though...?

Mike

[Screwdriverone]

Hmm, yes that's where I mean, must be the active HII regions I am talking about or my monitor... Never fear, I will pull my head in. ;)

As you were! :D

Cheers

Chris

[strongmanmike]

:lol: no need for that, nose on screen does that :thumbsup:

[alpal]

Wonderful pic Mike.
It compares well with this APOD from Gendler:
http://apod.nasa.gov/apod/ap090919.html

http://www.robgendlerastropics.com/NGC3621.html


& even ESO with their 2.2m telescope!
http://www.eso.org/public/news/eso1104/

You have proven that amateurs are catching up with professionals.

well done

cheers
Allan

[Rod771]

Very nice image Mike!

My eyes actually kept getting drawn to PGC 34490, little bit of nice detail there :thumbsup:

No flats, yes that would be nice. :)

[gregbradley]

Very nice Mike. It is a faint one. Great colour and detail and as always your stars look great.

Greg.

[atalas]

Looks great!

[strongmanmike]

Hi Al, yeah saw all those already, was looking at Gendlers and its great but the sharpening artefacts are a bit obvious aaaand just to annoy everyone I wanted a little more colour :D :lol:



Cheers Rod, yes that galaxy is very cool, just big enough to show some cool shape but small enough to look reeeeally far away :P and yes, not needing darks or flats and usually no need for gradient removal or much noise reduction is a great capability and makes processing so quick and easy.



Thanks Greg, yes the outer arms are indeed faint, in fact Martin needed some 8hrs of Lum binned 2X2 for these outer arms in his version...12" @ F3.8 with this little sensitive Sony chip has some advantages ;)



Cheers Louie

[RickS]

Nice one, Mike! Looks great. And colourful of course :D

[Shiraz]

:thumbsup: that sure is a very fine image. pretty impressive being able to image something that well at 22.3 M/arcsec2

[strongmanmike]

Cheers boys :thumbsup: yes Ray, I wish I had a 20" version of this scope...which arhem.. is about to be released by Orion Optics this year ;)

Mike

[marc4darkskies]

Great data & detail Mike but the garish colours in this one spoil it for me I'm afraid.

Cheers, Marcus

[strongmanmike]

Ahhh it's Beige Davies :lol: Garish Garish huh? :sad:...fair enough :sadeyes: :) ...but hang on, you don't like narrowband colours either (fussy bustard)...meah, it's just a phase...it will grow on you too...it will if enough people can be expoooosed :D...maybe...:question: or I'll grow out of it :lol:...I prefer to call them vibrant :)

MIke

[alpal]

Hi Mike,
Gendler's published image is only 553 KByte in size:

http://apod.nasa.gov/apod/image/0909/NGC3621Lgendler.jpg

Maybe that explains the artifacts?
It's actually got some awful green parts just under the galaxy.
However - I think everyone -including me - has become a little too fussy lately.

As for the colour debate:
Maybe we need to publish 2 results with every image i.e.
- one with fairly tame pastel colours & another boosted with LAB mode
in order to please everyone? :)

cheers
Allan

[strongmanmike]

Ah nah, it's all good, differing opinions is a healthy thing as long as we don't get too wound up and cranky (:mad2:) :lol:

As for Robbo's image and I'm not criticising juuuust observing :whistle:, there are tell tale signs of de convolution remaining on the stars, they are bright points inside more defuse discs and the background is evenly speckled, the gradients are pretty obvious too :shrug: I know the theory is probably sound but I always doubt the accuracy of deconvolution and how people apply it, how does the filter know to shrink a feature so that it remains the actual shape it should be rather than just get shrunk to a point with arbitrary or in fact differing shape and thus simply creating more of an illusion of higher resolution...?There is also a magenta hue to the core area too..ok, ok sorry Rob not being critical it was an APOD after all ;) :lol:

Mike

[LewisM]

Wha???? No jets??? It's not a True Sidonio.

Seems to be some star elongation Mike - unusual for you.

[strongmanmike]

Jets, always jets with you, everywhere jets :rolleyes: :lol:

[LewisM]

Its the aviator in me :)

[strongmanmike]

Ah I see, thanks for the comments

[graham.hobart]

An awesome spectacle on the big version Mike. Really lights up and the background fuzzies are amazing, give it a nice perspective.
Surely a book of your pictures can't be far away!!
:thumbsup::thumbsup:
Graz

[strongmanmike]

Ah thanks Graham one mans "lights up" is another mans "Garish" :lol:

Book?...yeah, maybe one day...

:thumbsup:

Mike

[RickS]

Mike,

The theory is sound and so long as you know the point spread function it should work perfectly. In practice you have to estimate (or guess) the PSF. Also, the decon implementations in packages like PI and CCDStack can only deal with a single global PSF when in real life the PSF can vary across different parts of the image.

Still, you can get reasonable results in PI so long as you have data with good SNR and don't push it too far. It has a nice tool, DynamicPSF, which helps estimate the PSF.

Cheers,
Rick.

[Stevec35]

Pretty good effort Mike. It's a deceptively difficult galaxy this one.

Cheers

Steve

[Logieberra]

Mike.Nice! How you enjoying the seeing out that way? Any stats? How does it compare to the Cbr burbs? Darker, no doubt :)

[SkyViking]

Beautiful image of a beautiful galaxy, Mike :) There is a lot going on in that image and it seems you captured all the faint outer parts. Some interesting background galaxies too, and the little spiral above is cool :thumbsup:
It could be very interesting to see a side-by-side comparison with a version from your FLI.

[astronobob]

Grouse one Mike, , amaizing details in the Galaxy central dust lanes ! Im flat out getting such in Andromeda :)
Always dig your colour processing aswell.
Another Mighty fine show of your work :thumbsup:

[strongmanmike]

All my understanding too...

But in a nut shell, if not applied using area/feature specific valid PSF's it is indeed creating an illusion and potentially simply making small bright irregular shapes in, say a galaxy arm, into small dots with new shapes that when viewed as a whole makes an image or area of an image look sharper but it is no longer the real detail as it were :shrug:...I'm still out on this but granted when applied well it can make the image look higher res, so I guess that's part of it anyway :lol: :question:



Yeah quite a faint outer arm area with this one



Hi Logan, hard to scientifically quantify seeing, even when scouting for pro observatories, so anecdotal is the best we can do I guess...and with this in mind I think the seeing here at Wallaroo is probably about as good as I remember Canberra being when I was imaging from Campbell during the second half of 2006, maybe marginally better? It was probably a little better seeing and more consistently so when I lived at Googong though, where I was at almost 800m ASL imaging with the Starfire during 2004-2006 (was a drought on). It is obviously noticeably darker here at Wallaroo than Campbell and about the same as Googong although when I lived in northern Ngunnawal in 2002 the skies there were quite dark except to the south and the seeing again was about as good as here ie some good nights some crap :shrug: I did have a good handful of nights with what I would class as exceptional seeing at Googong but so far, although I have had a few nights I would call good, I have probably only seen one or two nights from Wallaroo that I would describe as getting close to exceptional seeing and that was the nights I did THIS (http://www.pbase.com/strongmanmike2002/image/151629696/original) image and THIS (http://www.pbase.com/strongmanmike2002/image/152595656/original) image.

Tis certainly rather windy here (did I ever mention that :question: :P)...but the dome stopped that issue in its tracks :thumbsup:

Not sure all that was really all that meaningful :lol: but I can say this - as far as seeing goes, all sites I have used in the Canberra region are better and more consistently so than anywhere I imaged from around Newcastle between 2008 - 2012 and excellent dark skies are only a 20min drive beyond the edge of Canberra but are only found driving much further from Newcastle and even then they are not as good.



Cheers Rolf :thumbsup: it came out ok in the end I guess and seems to compare favourably with the few examples available on the net done with larger longer FL scopes.

What are you thinking with the FLI?...less resolution..? Maybe I should image something I did with the ProLine from here just to compare...? Have you heard of the Antennae galaxies by any chance :whistle: :lol: maybe I should do those with the new setup? ;)



Thanks Bob, love your easy attitude and warm candour, should be more of it on here :thumbsup:

MIke

[SkyViking]

Yeah, just thought it might be an interesting experiment, having a direct comparison between the two imaging systems. Maybe the newer chip is better, less noise etc. but on the other hand the FLI has more cooling.


I vaguely recall the name :P Actually I'm having a rather intimate relationship with these very galaxies at the moment, lol. Around 25 hours collected so far, but more to come of course. :thumbsup:

[strongmanmike]

Problemo is that I don't have a OAG solution available for the ProLine+AG12 combo :sadeyes:



Yeah I knew you were stealing all the photons from Paul on this one :lol:

Sounds like it will be spectacular...wish it was easier to collect mega data :sadeyes:...or I could find the concentration and will again :lol:

Mike

[SkyViking]

I'm sure there are enough photons to go around :thumbsup:
Or did I notice a brief darkening of the sky when I pointed my scope upwards yesterday night...:question: :lol:

[alpal]

Hi Mike,
I would say that deconvolution applied to high signal to noise ratio areas
definitely increases the correct detail.
In low signal areas it tends to make a false grainy look that can only
be remove by adding noise such as in this helpful example:

http://bf-astro.com/backgndRepair.htm

I used this technique on my NGC 1808 galaxy background
on flickr which had super high noise.
Stars & low signal areas should be masked when applying deconvolution.


cheers
Allan

[strongmanmike]

Thanks for that Allan, had seen that article before but never put it into practise...must have a go on one of my uncalibrated images ;) :thumbsup:

Mike

[tilbrook@rbe.ne]

Wonderful image of 3621 Mike!:thumbsup:

Like the strong colours, I think it really defines regions in the galaxy.

Cheers,

Justin.

[strongmanmike]

Hey thanks Justin and glad you like the garish colours :lol: (meah, like olives and anchovies either love'em or you hate'em)

All good :thumbsup:

Mike

[alpal]

Hi Mike,
it's one of the greatest processing tricks I've ever seen.
Notice how he doesn't lose that faint galaxy?
The mouse over on the final picture is amazing.

cheers
Allan

[prokyon]

Great work, Mike! You captured so many faint details. And I like the colors.

Cheers

Werner

[SkyViking]

Ouch, that seems a bit too Photoshopped for my taste :lol:
There is certainly an improvement to the image, but as he states on the page it is really a "last gasp effort". I think replacing 99% of the image with a subjective artificial background, complete with fake noise, is pretty much in the same category as selective brightening and lassoing etc.

[alpal]

99% - I don't think so - he's replacing false lumpy looking noise with
a more perfect even noise without losing the faint details of that galaxy.

[Bassnut]

Thats a cracker Mike, given its dim, and as usual your star field is excellent.

[SkyViking]

He's replacing what came out of the camera with something artificial which didn't come out of the camera, that's really the issue for me.
In the example literally 99% of the image, the entire background, was replaced. In the final result the noise floor has been lowered, but no further details are present - implying that they don't exist, which is probably not true.
Anyway just my opinion, back to Mike's thread :)

[nandopg]

Hi Mike,
What a great image, and the star field is just beautiful with all of those galaxies very well resolved showing up there.
I love your minimalist approach of processing and share the same opinion about the excess of use of deconvolution that we see occasionaly here and there.
Congratulations for the wonderful outcome,
Fernando

[strongmanmike]

Thanks Werner glad to hear it :thumbsup:



Cheers Bassnutstarremover :)



Thanks Fernando, yes I think decon is over used, I have rarely used it myself (mainly because I only use Astroart and generally haven't been happy with the results it's implementation of Decon produces) and never the less seem to be able to extract good details (http://www.pbase.com/strongmanmike2002/hubble_comparisons) with other sharpening techniques :D

I really do need to give decon a go via another piece of software though :question:

Mike

[Logieberra]

Mike, thanks for the write up on your Canberra (and now Wallaroo) seeing experiences. That does help! I hear the bush calling me. In a few years perhaps. And as you said, Canberra - not the best of seeing - but plenty of clear, average nights. We're doing OK down here :) Cheers.

[marco]

:prey2:

..fantastic resolution and processing there!

Heat off Mike!

Clear skies
Marco

[rogerg]

Mike,

I may have missed a memo in a previous thread, so sorry if I am repeating what has been covered and please direct me else where if required.. ;) but … I’m sure I remember you using a FLI before, now a Starlight Express – have you switched cameras or is this a different scope? Is the SXVF-H694 a new piece of kit you have? :question:

Regards,
Roger.

[AG Hybrid]

A familiar picture (http://www.orionoptics.co.uk/) on the front of the Orion Optics webpage ;)

Might take a couple goes to load the right one.

[strongmanmike]

No need for Bowing Marco I am apparently a mean and nasty poster about peoples images, I think I have been particularly hard on your horrible wrecks of images :lol: ...eerrrr?..pleeease confirm you knew that wasn't thinly disguised sarcasm meant to offend :prey:



No problemo, we live in quite an astronomically friendly region really :thumbsup:



Hi Roger, yeah I have been using the SX gear since middle of last year on the AG12, quite happy with how it is working out too, the OAG is very useful. The FLI is an awesome camera though with a huge chip and will hopefully make a come back into service on a longer FL scope some time in the future :thumbsup:



Cheers for spotting that Adrian..hadn't seen it, cool :)

[madbadgalaxyman]

Hi there mike,

You did a good job bringing out the outer arms. But this is a very challenging object in its outermost portions.

As mentioned in my post in rogerg's recent imaging thread about this galaxy, the disk is not at all normal, and it is quite easy to see in your image that one of the major outer arms actually bends a long way out of the plane of this galaxy!

The arms have an "unevolved appearance" as do those of NGC 1512, as these galaxies have very extended disks which are easiest to pick up in the UV images from GALEX. As we once discussed regarding NGC 1512, one can imagine that these faint but optically-evident disks are still forming from gas falling into the gravity well of a galaxy;
it is virtually certain that the era of disk formation has not yet finished in the universe, for instance some astronomers found that the disk/spiral region of M33 had very gradually formed, starting in the inner part and then working outwards.

Just for fun and profit, here is the UV image of N3621 from GALEX:

179950

An obvious bending or twisting of the arms, out of the primary plane of this galaxy, is more obvious in this UV image.
(and I can prove my case with an image which shows the HI gas disk bending in some weird way)

Best regards,
Robert

This galaxy was recently discussed in the third post of this science thread:
http://www.iceinspace.com.au/forum/showthread.php?t=133011

The comparison with NGC 6744 is an interesting one.

[AlexSavoy]

Some very very nice colors and quality of shot here. Such a low mag aswell.... good effort.

[Geoff45]

That's a magnificent photo Mike. I know from personal experience that this is a really difficult object and you've done it proud. I had a go at it at the SPSP but I had lotsa trouble processing it. Similar detail to yours but a crappy background. Well done!
Geoff

[strongmanmike]

Cheers Geoff :thumbsup: ah sigh..another year has gone by.....:sadeyes:

Mike