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Loop surrounding the spiral galaxy NGC 5907 ?

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#1 Erik68

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Posted 10 May 2022 - 07:07 AM

HI!

 

Has anyone been able to observe the loop around NGC 5907?
5/8/2021. Observing NGC 5907 (14 "f / 4.2) showed me a trace of a piece of loop? (120x + No8 filter light yellow). Conditions were excellent (NELM 6.5mag +) for my backyard.

 

BEST!


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#2 David Knisely

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Posted 10 May 2022 - 10:03 AM

Nope, under a dark sky, NGC 5907 just shows up as a nice narrow sliver of light.  At my dark sky sites, at moderate powers, I can see a little dust lane detail along some of its length in my 10 and 14 inch Newtonians, but not much else.  However, it is a pretty object to look at (and it seems to benefit from viewing it at moderate power rather than with any sort of filter in the optical train).  Deep DSS images also show no sign of any ring or loop.  Clear skies to you.


Edited by David Knisely, 10 May 2022 - 10:05 AM.

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#3 Astrojensen

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Posted 10 May 2022 - 11:00 AM

Deep DSS images also show no sign of any ring or loop.  

But it does in fact have one: https://en.wikipedia...llar_stream.jpg

 

https://www.insighto...-with-tail.html

 

http://www.capella-o...NGC5907Prim.htm

 

 

Clear skies!

Thomas, Denmark


Edited by Astrojensen, 10 May 2022 - 11:02 AM.

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#4 Mark SW

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Posted 10 May 2022 - 12:45 PM

But it does in fact have one: https://en.wikipedia...llar_stream.jpg

 

https://www.insighto...-with-tail.html

 

http://www.capella-o...NGC5907Prim.htm

 

 

Clear skies!

Thomas, Denmark

Thomas,

Thank you for the photographic links. 

Has it been confirmed visually?  

 

Thank you

Mark



#5 Raul Leon

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Posted 10 May 2022 - 12:53 PM

Hi , pretty sure Mel Bartels has seen it and sketched it!


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#6 Mark SW

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Posted 10 May 2022 - 01:06 PM

Hi , pretty sure Mel Bartels has seen it and sketched it!

Thanks Raul

I read Steve Gottlieb reports with telescopes from 8" to 48" from 1981 to 2017 and did not see a reference to any loop.

I know I never will see a loop.


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#7 Erik68

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Posted 10 May 2022 - 02:12 PM

The brightest parts have a surface brightness of 27-28mag / arc.sec2. This is the brightness of the UMi Dwarf Galaxy and Draco Dwarf, which can be seen through medium-sized telescopes.
The loops are formed by old yellow stars, a remnant of a disrupted dwarf satellite galaxy, so the best solution is to use a light yellow filter (No8)

Hi , pretty sure Mel Bartels has seen it and sketched it!

I think I've seen all of Mel's sketches, but NGC 5907's sketch is not there.
 



#8 David Knisely

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Posted 10 May 2022 - 06:06 PM

But it does in fact have one: https://en.wikipedia...llar_stream.jpg

 

https://www.insighto...-with-tail.html

 

http://www.capella-o...NGC5907Prim.htm

 

 

Clear skies!

Thomas, Denmark

Well, the question more concerned whether anyone had actually seen the loop visually (which I answered in the negative) and not whether it actually has one or not.  If I push the DSS images enough, I can get a hint of part of the loop to the east-northeast of the southeastern portion of the galaxy, but I wouldn't have noticed it on the image unless told about it and searching for it beforehand, so it is definitely somewhat into the "noise".  Certainly, it is notably fainter than the three tidal "prongs" and northwestward plume of M51's companion, which prominently show up on the DSS images without processing and which I have seen in my 10 and 14 inch Newtonians.  Thus, from this information, it gives me at least some doubt that the loop structure around NGC 5907 may be a visual feature.  I may try with my 14 inch again from the darker skies of the Nebraska Star Party later this summer (perhaps trying with my broad-band filter), but I don't have a lot of hope about seeing much of the loop.  Clear skies to you. 


Edited by David Knisely, 10 May 2022 - 07:42 PM.

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#9 Erik68

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Posted 11 May 2022 - 06:51 AM

Sketch made with the eyepiece of the telescope.I did not know the exact location of the tail stream,inspecting the area around NGC 5907, I came across a brightened oblong field, already visible through the No 8 filter.

 

CN.jpg

 

 

BEST!


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#10 Astrojensen

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Posted 11 May 2022 - 10:50 AM

Erik68 take a look at this. I do not know if it helps or not.

 

https://docs.google....zBhOTkxZDdlMTFi

Wrong galaxy, so that really doesn't help much... grin.gif  

 

 

Clear skies!

Thomas, Denmark



#11 Mark SW

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Posted 11 May 2022 - 11:27 AM

Wrong galaxy, so that really doesn't help much... grin.gif  

 

 

Clear skies!

Thomas, Denmark

OOPS

post deleted


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#12 Mark SW

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Posted 11 May 2022 - 11:41 AM

This is better 

 

https://docs.google....TUxMjdkMGI4MjYy


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#13 Erik68

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Posted 11 May 2022 - 12:29 PM

Wow 48 "! .... monster dobs.Thanks Mark SW!

I think you can go down a lot, with an aperture like 20 "or a smaler.Perhaps under the sky of Bortlea1, even14 "is enough. The problem is that people do not try to observe various extreme objects, I will mention IFN and the wonderful observations of Mel Bartels.

 

 

BEST!


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#14 j.gardavsky

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Posted 11 May 2022 - 12:30 PM

Hello Erik,

 

and thank you for the info.

 

- First of all, there is a mass of literature on the NGC 5907 with its tidal streams.

- Second, as the high étendue telescopes and even binoculars reveal the IFNs in our Galaxy, I am ready to believe that the bright tidal streams on some galaxies may become visually observable, given a sufficient telescope aperture, and all what's needed.

 

Otherwise, it's interesting that a long pass filter has been working for you.

Intuitively, the tidal flow might have a sufficiently high compression to allow the longer wavelengths Mie scattering of light to dominate, or alternatively the galaxy bulge might have a "warm" color index resulting into the light reflected on the longer´wavelengths.

Otherwise with the Rayleigh scattering, a blue filter would be better suited for the tidal flows.

 

Best,

JG

 

It would be great to see a sketch from an independent visual observation.


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#15 Erik68

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Posted 11 May 2022 - 12:59 PM

 

 


Otherwise, it's interesting that a long pass filter has been working for you.

Intuitively, the tidal flow might have a sufficiently high compression to allow the longer wavelengths Mie scattering of light to dominate, or alternatively the galaxy bulge might have a "warm" color index resulting into the light reflected on the longer´wavelengths.

Otherwise with the Rayleigh scattering, a blue filter would be better suited for the tidal flows.

In 1996, following the galaxy's color index, I started using the No8 filter (light yellow) when observing the E and SO galaxies.
I forgot to add that a part of the loop was not visible without a filter.

 

 

PS. I wanted to thank you too, because thanks to your IFN observation, I fell in love with nebulae, and also bought a Baader CCD blue ...


Edited by Erik68, 11 May 2022 - 01:00 PM.

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#16 j.gardavsky

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Posted 11 May 2022 - 02:08 PM

Hello Erik,

 

and thank you very much for sharing your experience!

 

The visiblity of the tidal flow through a long pass filter, and its disappearance without a filter, sounds like supporting an idea of the reflected and scattered light from the bulge.

 

It has been also my experience with the filters on the galaxies, that the bulge and the dark lanes become better visible through the long pass filters. Nice to see, that you are confirming it.

 

I have put a note in my sky atlas on this galaxy.

 

Best,

JG



#17 Mark SW

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Posted 11 May 2022 - 03:34 PM

Here are three results from the sketching forum

 

https://www.cloudyni...7#entry11867618

 

https://www.cloudyni...7#entry10286792

 

https://www.cloudyni...7#entry10141796

 

PS Erik68 keep us posted


Edited by Mark SW, 11 May 2022 - 03:55 PM.


#18 Erik68

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Posted 11 May 2022 - 04:01 PM

Cool sketches.
The problem is that you cannot see such fleeting objects without consciously looking for them.
The aperture is not everything, you need a sufficiently wide field, maximum exit pupil and well-chosen power.
Experience in observing this type of objects is key, as is the ability to catch subtle differences in the brightness of the background.
IFN observers know it well.

There are many sketches of the M81 galaxy, through telescopes of various sizes, but you can hardly see any traces of IFN ...

 

 

 

BEST!


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#19 Keith Rivich

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Posted 11 May 2022 - 05:22 PM

I looked at 5907 at TSP under pretty good conditions. I tried for the tidal tail and came up completely blank. I observed this on the same night I observed the tail in 3628. 


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#20 maroubra_boy

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Posted 11 May 2022 - 06:08 PM

Cool sketches.
The problem is that you cannot see such fleeting objects without consciously looking for them.
The aperture is not everything, you need a sufficiently wide field, maximum exit pupil and well-chosen power.
Experience in observing this type of objects is key, as is the ability to catch subtle differences in the brightness of the background.
IFN observers know it well.

There are many sketches of the M81 galaxy, through telescopes of various sizes, but you can hardly see any traces of IFN ...

 

 

 

BEST!

I would add to your comment that most people don't know what is visible.  Not so much consciously looking for them, just don't know to expect more (or maybe I'm just saying the same thing as you).  They only see what they expect to see, but not everything that is actually visible.  Some people may see IFN's, but by not knowing any better as a result dismiss IFN's and streamers as aberrations.  My own sketching has allowed me to see deeper than what my immediate first few minutes of observations ever gives me.  But how many people would also be spending 45 minutes to two hours on just one object?  My dobs are also non-tracking, so the constant nudge-nudge-nudging helps to keep refreshing my eyes.  For people with tracking scopes, it takes practice for the repeated tapping of the OTA to become second nature to achieve the same refresh, otherwise they end up seeing less.

 

I have found this thread fascinating.  I have only recently become familiar with IFN's and Mel's work - I've started corresponding with him too about this.  This sort of thing is much better developed for the northern hemisphere, and more work needs to be done here in the southern hemisphere.

 

Alex.

 

EDIT:  Come to think of it, many imagers wouldn't know about this sort of thing either, and if they did come across it they may actively seek to remove it because it doesn't fullfil their notion of what the object should look like.  They may even do this editing out because these extensions reach out beyond what the size of the frame allows for.  Something like taking a photo of someone but their head is out of the frame...  

 

This thread and related discussions I've been having is now making me re-examine how I approach my observing in the future.  JG, I have read a few times now about your use of filters with galaxies too.  All of this is doing my astro mojo no end of good :)

 

Alex.


Edited by maroubra_boy, 11 May 2022 - 06:17 PM.

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#21 rustynpp

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Posted 11 May 2022 - 06:14 PM

What is an IFN?

Cheers,
Nick

#22 maroubra_boy

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Posted 11 May 2022 - 06:20 PM

Integrated Flux Nebulae.

 

Also called Herschel's Ghosts.

 

Long been observed, short time been identified and very little known about in the wider amateur ranks.

 

This article of Mel Bartel's will help:

 

https://www.bbastrod...els Ghosts.html

 

Alex.


Edited by maroubra_boy, 11 May 2022 - 06:23 PM.

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#23 maroubra_boy

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Posted 11 May 2022 - 06:34 PM

From Mel's article, you will notice that IFN's are visible in as small an aperture as 6"!  But the optics are FAST, f/3 and faster!  THIS is the trick, it requires fast optics.  And we have been on the most part led to believe that the f/ratio has little impact on viewing, being more just a photo thing, and that a larger secondary mirror is a very bad thing...  Try telling Mel that.


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#24 Astrojensen

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Posted 12 May 2022 - 01:36 AM

From Mel's article, you will notice that IFN's are visible in as small an aperture as 6"!  But the optics are FAST, f/3 and faster!  THIS is the trick, it requires fast optics.  And we have been on the most part led to believe that the f/ratio has little impact on viewing, being more just a photo thing, and that a larger secondary mirror is a very bad thing...  Try telling Mel that.

If this is so, then how come Herschel saw the IFN, with his very slow telescopes? I believe he first saw the IFN above M82 with his "20-foot" telescope, which has around 18" aperture and is f/14 or thereabout. Herschel had no scopes faster than f/5. I'll need to read through his memoirs, to see if I can find out what he used. 

 

But it's true, that getting the very bright images and wide field needed for the best views, is most easily achieved with a fast f/ratio. 

 

 

Clear skies!

Thomas, Denmark



#25 maroubra_boy

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Posted 12 May 2022 - 02:36 AM

Thomas,

 

You make a very good point, and I've been pondering this.

 

Here's one thought that comes to mind - Herschel didn't have any preconceptions about what he was to expect at the eyepiece, so while panning his scope he may well have noticed variations in illumination cross his field of view, oh-so-subtle variations, but enough for him to notice them.  And having no idea what his Ghosts were about, whatever notes he made would have puzzled his thinking and that of others who read his work.  Don't forget, OUR notion of what a galaxy is is only around 100 years old, and IFN's even more recent!  With IFN's being only a relatively recent identified thing, they would have gone largely unknown by all but very astute observing eyes, but with so little information about this, most IFN's would have been going by totally unnoticed.  Gee, some IFN's are also visible to the naked eye, but how many people even know about this!!!!!

 

Also, even with a slow scope it is not to say IFN's are not visible.  But it would take a very keen and unbiased, uncorrupted eye to notice them.  By uncorrupted I mean not prejudiced by notions of what SHOULD be visible vs accepting what IS visible and letting this guide your observations.  And because these IFN's are also as streamers mottled in structure, a keen eye would have been able to pick up these rare & subtle illumination fluctuations, with the less dense areas remaining invisible.  Mel's sketches note this too.  A faster scope allows not only for easier observation of IFN's, but also to form the needed big picture.

 

From my own observing I have come across curious fluctuations in the illumination in my FOV, but not knowing any better AND corrupted by my "knowledge" I paid no notice to them other than a fleeting "oh, what's that?" and nothing more, thinking it must have been some reflection or something.  But a log of those observations has remained in my brain as an oddity that my brain didn't dismiss outright.  I do recall having seen something  a few times.  This is why I have composed this post.  And this is also why I am curious to explore IFN's.  My difficulty is having the time to go bush, real deep bush to Bortle 1 skies.  Good to know I am not totally mad on my own... :lol:

 

I am most curious to know what IFN & ISM (Interstellar Medium) is visible south of the equator.  This is certainly something that VERY few people know anything about.

 

Alex.


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