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Bright Face-on Spirals at High Power

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#1 Araguaia

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Posted 26 June 2019 - 07:17 AM

Last night I was observing M83, seeing the three spiral arms get progressively easier to see as I increased power from 51x to 109x to 277x.  While at low power this galaxy is a large bright round patch with just a hint of swirl, at high power the general brightness decreases, allowing detail to be seen better.  Spaces between spiral arms become darker, and "gaps" in spiral arms contrast more with knots of brighter nebulosity.

 

I usually stop at 277x.  My next eyepiece would be a 3.5mm Nagler with an 82 degree field.  Things drift fast across such a field, at 435x, and good focus is hard to get unless seeing is good.  Also, faint objects become much fainter, except for planetary nebulas, which tend to magically become brighter.

 

But last night I decided to pop in the 435x on M83.  At first I was surprised by how small the core had become - at 51x the galaxy looked like 80% core, but now it was just a small ball of fuzz.  The spiral arms seemed to have vanished.  But as I improved the focus and jiggled the scope in order to track, the spiral arms popped into view, first in averted vision, then in direct vision.  This was interesting - they started out barely detectable, but soon they were filling the field, and I could trace them much closer into the core than before.  Just as far out, as well, but with much better resolution of the knots and gaps.

 

Encouraged by this, I decided to try it on another face-on spiral: M101.  It was peaking at 25 degrees altitude.  Maybe the seeing would not support it.  But to my surprise, after a few moments, the spiral arms just popped, and again I could trace them further in, and see more detail in the outer reaches - all those HII knots!

 

I nudged the scope over to M51.  I saw the "bridge" at 277x, at the limit between AV and DV.  But at 435x, once it "popped" (again, that delay of a few moments during which only the reduced core draws attention, and the rest seems to have faded away), I could see the bridge easily with direct vision, and hints of the dark lane that accompanies it.

 

Finally, I looked at M104 at 435x as a control.  On this bright edge-on the higher power did not show much more than 277x did.  It did generate a pleasing observation as the galaxy "scrolled" through the field, letting me appreciate each detail in turn.  But for the bright face-ons, I was surprised to find how much more detail I could see - how the dimming of the image actually made dim features more visible, once your eyes get used to it.  Can't wait to try this on NGC 1365 and M33 later this year.


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#2 Migwan

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Posted 26 June 2019 - 09:46 AM

Nice, wish 83 could only show itself here.  What kind of exit pupil do you have at 277x and 435x?



#3 Araguaia

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Posted 26 June 2019 - 10:05 AM

1.10mm and .70mm



#4 jayrome

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Posted 26 June 2019 - 10:47 AM

Nice going! I was doing some observing from my balcony last night because I was stuck at home. Bad light pollution. Could barely make out any spiral structure in M51 at x127, and M101 was just a large, faint fuzzy blob. Oh well, c'est la vie.



#5 Philler

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Posted 26 June 2019 - 06:48 PM

Nice post Araguaria.   What size scope were you using?

 

When I was a newbie in the 1980's I was fed some of the prevailing deep sky object myths like, "galaxies are for lower powers," and "you need a fast focal ratio scope."   My 12.5" f/6 is not only a great planetary scope, but also great on galaxies and other dso's.    Most important is what you are saying I have found to be true; experiment with different magnifications. I'm not shy about trying 200x and up on galaxies.


Edited by Philler, 26 June 2019 - 09:44 PM.


#6 Araguaia

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Posted 27 June 2019 - 06:09 AM

I used a 12" Dob with 30mm, 14mm, 5.5mm, and 3.5mm eyepieces.

 

Last night I was at it again.  This time seeing was bad - at 435x, the core of M5, near the zenith, was a soup with a few blobs.  But the same 435x still worked great on the bright face-on galaxies.  I tried it on M64, M94, NGC 4565, and Centaurus A, and it showed more detail on all of them despite the seeing.  On M51,  though, this time I could not hold the bridge in direct vision.  


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#7 Philler

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Posted 02 July 2019 - 07:06 PM

Careful viewing, trying different ep's, taking one's time always pays off over just trying to bag the most galaxies.  Well done, Araguaia.



#8 Araguaia

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Posted 03 July 2019 - 06:33 AM

Last night I gave some quality time at high power to NGC 4945 in Centaurus.  This bright edge-on used to look like a broad streak of light to me, and the glare of nearby stars made it hard to see detail.  Later, at high power, I became able to see a broad off-axis dark lane on it.  But last night for the first time I saw that the streak of light was not homogeneous - that there is a brighter, loose elongated S-shape running through it.  I went back and forth between 277x and 435x, and eventually was able to hold this S-shape at the limit between averted vision and direct vision.  One side of the S ran across the edge of the dark lane and seemed narrower than the other.  At the center of the S was a slightly brighter region.

 

Looking at the AP of NGC 4945 below, I realize that I was seeing the far spiral arm beyond the dust lane, the bright (although partially obscured) core, and the thin but bright arm full of HII regions running in front of the dark lane at the upper right part of the picture. 

 

NGC-4945-LRGB-v09-Final-03_kehusmaa1024c


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#9 jayrome

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Posted 03 July 2019 - 08:54 AM

I was back at it myself last night, and this time off to a dark-sky site (Class 2) - during the day I had checked forecasts and all was indicating clear, clear skies with good seeing. I have to say, M51 came alive, and at times, as I peered through the 10mm eyepiece, seeing and focus got so good that I could see a sparkling across the face of the Whirlpool. The spiral arms were also clear and distinctly defined, absolutely glorious.

Had the same effect when observing M82, a distinct, distant sparkle of small stars that would come in and out of visibility.

Also, the Andromeda galaxy is now starting to get good, getting high enough in the sky by 1 am EST for some very pleasant observing.

 

clear skies amigos.



#10 Philler

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Posted 03 July 2019 - 07:30 PM

Good to know about 4945.  The only times I've viewed it was from SW Texas low in the south in Centaurus.


Edited by Philler, 03 July 2019 - 07:31 PM.


#11 Astro-Master

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Posted 04 July 2019 - 01:06 AM

Last night I was observing M83, seeing the three spiral arms get progressively easier to see as I increased power from 51x to 109x to 277x.  While at low power this galaxy is a large bright round patch with just a hint of swirl, at high power the general brightness decreases, allowing detail to be seen better.  Spaces between spiral arms become darker, and "gaps" in spiral arms contrast more with knots of brighter nebulosity.

 

I usually stop at 277x.  My next eyepiece would be a 3.5mm Nagler with an 82 degree field.  Things drift fast across such a field, at 435x, and good focus is hard to get unless seeing is good.  Also, faint objects become much fainter, except for planetary nebulas, which tend to magically become brighter.

 

But last night I decided to pop in the 435x on M83.  At first I was surprised by how small the core had become - at 51x the galaxy looked like 80% core, but now it was just a small ball of fuzz.  The spiral arms seemed to have vanished.  But as I improved the focus and jiggled the scope in order to track, the spiral arms popped into view, first in averted vision, then in direct vision.  This was interesting - they started out barely detectable, but soon they were filling the field, and I could trace them much closer into the core than before.  Just as far out, as well, but with much better resolution of the knots and gaps.

 

Encouraged by this, I decided to try it on another face-on spiral: M101.  It was peaking at 25 degrees altitude.  Maybe the seeing would not support it.  But to my surprise, after a few moments, the spiral arms just popped, and again I could trace them further in, and see more detail in the outer reaches - all those HII knots!

 

I nudged the scope over to M51.  I saw the "bridge" at 277x, at the limit between AV and DV.  But at 435x, once it "popped" (again, that delay of a few moments during which only the reduced core draws attention, and the rest seems to have faded away), I could see the bridge easily with direct vision, and hints of the dark lane that accompanies it.

 

Finally, I looked at M104 at 435x as a control.  On this bright edge-on the higher power did not show much more than 277x did.  It did generate a pleasing observation as the galaxy "scrolled" through the field, letting me appreciate each detail in turn.  But for the bright face-ons, I was surprised to find how much more detail I could see - how the dimming of the image actually made dim features more visible, once your eyes get used to it.  Can't wait to try this on NGC 1365 and M33 later this year.

For a real treat try using an Ethos or other high quality 100* eyepiece on galaxies.  Not only do you get higher contrast, but the whole galaxy is visible at high power, and it seems the galaxy stays in the field of view twice as long as an 82* field.



#12 Araguaia

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Posted 05 July 2019 - 07:03 AM

My 277x eyepiece is an ES 100o.  It fits most galaxies in their entirety, though not big ones like M101.  My next purchase will be a good 11mm EP - currently the next step up is a Meade 14mm that is not so good in the outer field.  But I think I can only afford an 82o.




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