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A Hunt for Spiral Arms and Bars

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#1 Araguaia

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Posted 10 August 2019 - 01:51 PM

Tomorrow is likely to be my last session for a while.  The Moon will set at 3:20 AM, and the sky is very clear.  After that the Moon will be out most of the night, and by the time it starts to set early enough for an evening session, the smoke is sure to be covering the sky.

 

I decided it will be a stroll through bright(ish) spiral galaxies I haven't seen yet this season.  Most of them are to the SE, and will be fairly high only just before first light.  It will be a bit of a race to get them all in between about 4:30, when they'll start to get high enough, and 5:15, when the Sun will be 18 degrees below the horizon - astronomical twilight, it is said, though the other night I thought the sky to the NE was already washed out by 5:00 AM, mostly due to the zodiacal light.

 

The plan is:

 

- NGC 1300 at 4:15 (60 degrees alt) - should see the bar, hope to see at least a hint of the arms.

 

- NGC 1433 at 4:30 (45 degrees), a new target for me - it is said to show arms to the patient.

 

- NGC 1566 at 4:45 (35 degrees) - usually shows a nice loose S shape.

 

- NGC 1672 at 5:00 (30 degrees) - logged last season as a TIE fighter shape, with much detail.  It was a bit higher, but the sky might be more transparent now...

 

I'll start with Uranus while sipping coffee and waiting for the last moon glow to fade. Between moonset and 4:30 I'll warm up for spiral arms with M33 and NGC 1365, which I have already observed the past few nights, stroll around the Fornax Cluster for a bit, and probably have a look at the eery Eye of Cleopatra.   I'll close with the rising Orion Nebula, of course, and enjoy the reds and greens just to spite the deniers... grin.gif


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#2 KidOrion

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Posted 10 August 2019 - 02:58 PM

NGC 7479 in Pegasus is a classic barred spiral. 

 

NGC 157 in Cetus will also show some spiral structure.


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#3 Araguaia

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Posted 11 August 2019 - 07:57 AM

A beautiful session!  12" Dob, 30mm, 14mm, 5.5mm, and 3.5mm EPs.

 

After Uranus, I started the hunt for spirals with NGC 157 - thanks for the tip, KidOrion.  It was right in Dobson's Hole.  At 51x I found a bright oval, slightly teardrop-shaped.  At 277x it would show a core with averted vision, and when the core appeared so did a swirl pattern in the halo, going clockwise.  I couldn't hold it in direct vision but it was quite clearly spiral.

 

NGC 1300 showed a bright bar right away, and soon showed the fainter stubs of its arms as well.  Not as easy to see them as with NGC 1365 - about as hard as the arms of M101.

 

NGC 1433 was an elongated patch, which only showed a hint of wisps around it after prolonged observing at 277x and 435x.  The toughest arms of the night.

 

NGC 1566 was spectacular, just as I remember.  A bright extended core with a superimposed S, trailing off a long way.  Almost as evident as the arms on M51.

 

NGC 1672 took a few minutes of observing to show the TIE fighter shape - it was rather low in the sky.  It must be very nice seen from further south.

 

I ended with a look at M42, the Double Cluster, and the Pleiades, awash in zodiacal light.

 

Five face-on spirals, besides M33.  A few years ago, I would have never imagined that I could see arms in so many galaxies if I gave it enough time...


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#4 Pcbessa

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Posted 26 August 2019 - 10:33 AM

Hello Araguia!

 

Long time, no see. Here in Scotland I have been away from observing due to the 3 month long bright nights, where the sky never gets dark.

 

And yesterday it was my first night with the scope, after this long pause. Whilst most of the night was focused in nebula hunting in Cygnus, I did noticed a mottled structure in NGC7338 in Pegasus, while I was searching for the Stephan's Quintext galaxies. The galaxy looked like a miniature of Andromeda galaxy with a prominent dark lane to one side. But I didn't pay much attention. I am sure it would reveal two faint arms in a very dark location.

 

I have these on my records (I still haven't looked at many galaxies)

 

Spiral Arms or bar structure (11 seen)
M51, clear spiral pattern
M101, faint arm seen top rightwards with HII nebula, mottled structure
M33, two faint arms, faint arm seen going to HII nebula trail down rightwards and another right upwards
M31, dark lanes seen left and also right, and evidence of a curving arm top part
M81, good spiral structure seen faintly up rightwards and down leftwards quite away from core, upper arm seems to have HII regions
M99, Coma Pinwheel, a clear mottled and barred structure, SEE AGAIN
M100, galaxy with faint evidence of spiral arms, SEE AGAIN
M66 a beautiful bar structure
NGC2903, signs of arms extended outwards, also two bright arms, one up, one down, one of them is NGC2905

M64, what a galaxy, this one also revealed a dark lane and a very large galaxy, but dark lane not as evident. to be observed again

M94 signs of arms, like a ring around nucleus

 

Uncertain observations (4 suspected)

M109 some evidence of structure, to be observed again

Ngc3607, spiral-ish??, to be observed again

NGC7338 in Pegasus, dark lane, a miniature M31, elongated large halo, to be observed again

N2403, face on galaxy, but arms not seen yet

 

Good candidates/ Not seen yet: Fireworks galaxy, N7331, N7479, M77, M74, Ngc 936, IC342, NGC4236, NGC5033


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#5 Starman1

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Posted 26 August 2019 - 12:30 PM

Pcbessa,

A nice list--the others on you list may show considerable detail, too.

One irregular with odd details is IC10, and you will encounter others as you go.  Surprised you didn't mention NGC253

-25° shouldn't be too far south for you to see some details in it, though it will be low from Scotland.



#6 Asbytec

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Posted 27 August 2019 - 09:03 PM

 

NGC 1300 showed a bright bar right away, and soon showed the fainter stubs of its arms as well.  Not as easy to see them as with NGC 1365 - about as hard as the arms of M101.

 

I missed NGC 1365 last year, but I did manage NGC 1300. 

 

To me, it's kind of hard to talk about seeing spiral arms without talking about how to see them. I mean, once you're set up and observing, dark adapted, and under dark skies. All that is given. In my experience with NGC 1300, I did not so much see the spiral arms themselves, rather I could see where they were. The arms were not well exposed like an image, of course. So, forget seeing that. What I saw was a bar, as you did, an a faint halo. We know the arms are in the halo, so that's a start.

 

What I did manage to see, over time, was a very soft darkening in the halo on both sides of the bar. Not all at once, and not at all easy. But, those very faint and rarely perceived darker regions in the halo defined where the arms were barely seen in the outermost and admittedly very dim halo outside them. Those are the spiral arms causing that extended dim halo. Again, not actual arms like we see in an image, but a dim part of the outer halo that is barely visible beyond the core and beyond the very faint darker regions. 

 

That is how I know I've seen them, by the faint signature they create in the halo beyond the dark interspace. I even caught a brighter knot in the NW of the halo, probably a "root" of one of the arms. I could not make out where the arms ended, the halo was just to difficult to perceive that amount of detail. That's what they look like to me in my aperture, not like an image as clearly brighter arcs.

 

The sketch below makes it look easy, if it were realistic you'd be "observing" your monitor for an hour just to catch a glimpse or two. Not unlike the real thing. 

 

NGC 1300 Rev.png


Edited by Asbytec, 27 August 2019 - 09:06 PM.

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#7 jayrome

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Posted 27 August 2019 - 10:06 PM

 

NGC7338 in Pegasus, dark lane, a miniature M31, elongated large halo, to be observed again

 

Pcbessa,

 

Do you mean NGC 7331 the main Deer Lick Group galaxy? There is an NGC 7338 but its like magnitude 17, what kind of scope do you have that you are seeing a dark lane there? grin.gif

 

I do need to get back soon and try to spot Stephan's Quintet.  I've also been frustrated by this trio in Draco - I can only make out 2 of the 3. NGC 5981, 5982 and NGC 5985. For some reason I couldn't see 5981. I'll have to be more patient next time. 

 

But I digress, I'm not sure if OP can see these galaxies that far north from the deepest dark forests of Brazil.


Edited by jayrome, 27 August 2019 - 10:06 PM.


#8 Jeff Young

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Posted 30 August 2019 - 04:28 PM

Pcbessa,

A nice list--the others on you list may show considerable detail, too.

One irregular with odd details is IC10, and you will encounter others as you go.  Surprised you didn't mention NGC253

-25° shouldn't be too far south for you to see some details in it, though it will be low from Scotland.

I can't get NGC253 from 54ºN; it never gets above the trees on my horizon.

 

M106 is another good one:

 

M106.2009.05.26.jpg

 

 

M33 can take a lot of work, but it's definitely one of my favourites:

 

M33.2008.11.30.jpg


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#9 Jeff Young

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Posted 30 August 2019 - 04:37 PM

Oh, and NGC2950:

 

NGC2950.2008.03.08.jpg

 


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#10 Starman1

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Posted 30 August 2019 - 04:46 PM

My site has tall trees, too.

My southern horizon is -55°, but the farthest south I can see at the site is about -40°.



#11 Asbytec

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Posted 30 August 2019 - 08:48 PM

Here's a tough one. NGC 1073. Below is the best digital image I found that closely resembles the visual appearance. 

https://www.cloudyni...0171022-231657/

 

This was a challenging observation. The core actually had a brighter knot to one (southwest) side. I recall not seeing the spiral arms, but only hints of indeterminate varying brightness in the halo, including a possible field star embedded in it to the north. It's amazing we can make out some detail in images we can sometimes not see at all. 

 

Trying to sketch it so others can see it, finding that balance between a realistic view and the realism that our monitors differ. It's amazing the tiny bar was actually visible. And by visible, I mean almost impossible. Almost. smile.gif

 

Below is my report of observation.

https://www.cloudyni...1073/?p=9064482

 

NGC 1073 rev.png




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