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Old 19-05-2020, 02:35 AM
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glenc (Glen)
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Planetary Nebulae

Planetary Nebulae are usually small and often difficult to find by star hopping.
They are the remains of a star that exploded and have a fairly short life.

The attached file lists 71 NGC and IC PN by magnitude and by size.
All the objects are brighter than mag 13, larger than 12" and south of Declination +50.

The columns are
Name NGC or IC
PNG galactic coordinates and name
RA and Dec. Right Ascension and declination (dd is dec in deg)
L" length in arc sec
Dist. approx distance in light years
Type. 1 stellar, 2 smooth disk, 3 irregular disk, 4 ring, 5 irregular form, 6 anomalous form
Mag of PN
Mag of central star
S.B. surface brightness
CON Constellation

Please post your observations of some of these PN.
Attached Files
File Type: pdf PN mag size.pdf (144.9 KB, 56 views)

Last edited by glenc; 19-05-2020 at 07:47 AM.
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Old 19-05-2020, 06:52 AM
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PN distances

Here are the latest PN distances in light years from the Gaia spacecraft.
The magnitude of the central star is also given.
Attached Files
File Type: pdf PN dist gaia.pdf (248.9 KB, 19 views)
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Old 19-05-2020, 07:22 AM
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Ngc 7293

The Helix nebulae is the largest bright PN.
It was discovered by the German astronomer Karl Ludwig Harding with a 4” refractor in about 1824.
The PN is mag 7.6, diameter 22’, 655 light years away and only 10,600 years old.
My 9x50 finder shows the PN 1.2 deg from mag 5.2 ups Aqr, and its central mag 13.5 star is easily seen in my 12” Dobsonian telescope.
A UHC filter improves the telescopic view. The nearby mag 11.1+11.5 star pair are 19.6” apart. (In the image they are below the PN)

The attached image is from Aladin.
Attached Thumbnails
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Old 19-05-2020, 09:32 AM
Saturnine (Jeff)
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That's quite a list to work through, should keep some of us amused for a year or two, I quite enjoy hunting down planetary nebs. Mind you I like hunting down double stars as well and the two can be happily combined while star hopping around. Can probably tick off a few dozen on the list already.
Thanks for posting the list.
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Old 19-05-2020, 10:20 AM
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mental4astro (Alexander)
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Glen, excellent resource. Thanks for posting it!

Also, there is a surprising number of planetary nebulae that are visible from under urban skies! And modest aperture, say up to 8" or 10" from the big smoke is VERY effective. An Oiii filter is a big help not just fixed in place in the eyepiece or filter wheel or slide, but also in a blinking paddle to swish between eyepiece and eye to help with tiny PN's to POP out.

A couple of weeks ago during this StayAtHome period, I was inspired to do a PN sketching marathon after my good friend Sergei Antonov mentioned that he had pinned many PN's from his home also in Sydney. So over two nights I managed to sketch 24 individual PN's, as it happened to go an even dozen on each night. Each night the sketches were done in two sessions - the first from 8pm to around 12am, and then from 2:30am to twilight as other PN's slowly came into view. And of course, in 6 months time another set of PN's comes into view.

With my 9" Maksutov, I used the one eyepiece for the sketches, a Vixen 12mm SLV, as it made for consistency of magnification, AFOV, contrast and context between sketches. The exceptions were for IC 5150 and the Helix where I used a Vixen 14mm SSW and a Vixen 25mm plossl respectively. These two PN's presented particular challenges that meant a different eyepiece was better suited, especially the Helix - it is so large and so faint that I used five different eyepieces to find one that gave the best image from my home in Sydney.

You will also notice that the PN's on the most part are not centred in each sketch. I wanted to also present the star field that gave the most interesting composition with each PN.

NGC 3699 is a particular fav of mine because it resembles a mini Centaurus A.

What was most remarkable for me was just how much detail can be seen in these PN's from under Sydney skies!

One thing that does have a big impact on all DSO's regardless if it is from a dark sky or urban skies, is quality of transparency. I had viewed NGC 6302, the Bug Neb., just a couple of nights before, and I could see more detail on that night as transparency had been better then than on the night I sketched it. So don't just look at a PN on one night and then forget about it. Revisiting it could mean scoring a night of very good transparency and pulling even more detail from it!

Sketches were done at the eyepiece using white and blue soft pastels on black A3 size paper. Each circle is approx the size of a fist.

Alex.
Attached Thumbnails
Click for full-size image (Planetary Neb marathon 1 LR.jpg)
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Click for full-size image (Planetary Neb marathon 2 LR.jpg)
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Last edited by mental4astro; 20-05-2020 at 06:36 AM.
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Old 19-05-2020, 03:12 PM
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Thanks Jeff and Alex.
Your sketches are great Alex, done from Sydney too with a filter.
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Old 19-05-2020, 10:18 PM
gaseous (Patrick)
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Thanks for the list Glen, very useful. Are PNs stars that have actually exploded? I thought they'd swollen and shed their outer gases before condensing into white dwarfs with the surrounding nebulosity. Back to school for me obviously.
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Old 20-05-2020, 07:10 AM
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Pat, what made you reconsider what PN's are from your initial thinking?

PN's are not super nova remnants. They are as you said the nebulosity left after a star has shed its outer layers, leaving behind the star's core, now termed a white dwarf. But not condensing back to form the white dwarf.

The white dwarf is not a star in the normal sense that is converting hydrogen into helium - its fuel has been depleted which is what triggered the disastrous shedding of a major % of its mass. The white dwarf is really nothing more than a cinder that is glowing from the residual energy created/generated inside the core eons ago, and is slowly bleeding out this energy until it has no energy to release and is a dead, cold and dark mass.

It may or may not have any of its original planetary system left still orbiting the cold core - don't forget that the planetary nebula phase saw an enormous amount of the star's mass lost, in turn meaning its also lost a huge amount of its original gravitational power, so much of the original solar system may have been also lost as the core alone does not possess the gravitational pull to retain the solar system - planets, comets, asteroids, etc.

Makes you wonder what a spent, cold stellar core looks like?

On the matter of stellar evolution (& sorry, a digression from the topic as this thread as sparked a question not totally unrelated though), what's with the stars that form globular clusters? These clusters are very ancient, but the component stars seem to defy what we know as typical stellar evolution - these stars should have gone past their main sequence phase a LONG time ago, yet so few PNs are ever seen in GC's and yet these stars keep shining, larger than our Sun, much older than our Sun, but still not evolved beyond main sequence...

Alex.
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Old 20-05-2020, 11:29 AM
gaseous (Patrick)
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Quote:
Originally Posted by mental4astro View Post
Pat, what made you reconsider what PN's are from your initial thinking?

PN's are not super nova remnants. They are as you said the nebulosity left after a star has shed its outer layers, leaving behind the star's core, now termed a white dwarf. But not condensing back to form the white dwarf.

The white dwarf is not a star in the normal sense that is converting hydrogen into helium - its fuel has been depleted which is what triggered the disastrous shedding of a major % of its mass. The white dwarf is really nothing more than a cinder that is glowing from the residual energy created/generated inside the core eons ago, and is slowly bleeding out this energy until it has no energy to release and is a dead, cold and dark mass.

It may or may not have any of its original planetary system left still orbiting the cold core - don't forget that the planetary nebula phase saw an enormous amount of the star's mass lost, in turn meaning its also lost a huge amount of its original gravitational power, so much of the original solar system may have been also lost as the core alone does not possess the gravitational pull to retain the solar system - planets, comets, asteroids, etc.

Makes you wonder what a spent, cold stellar core looks like?

On the matter of stellar evolution (& sorry, a digression from the topic as this thread as sparked a question not totally unrelated though), what's with the stars that form globular clusters? These clusters are very ancient, but the component stars seem to defy what we know as typical stellar evolution - these stars should have gone past their main sequence phase a LONG time ago, yet so few PNs are ever seen in GC's and yet these stars keep shining, larger than our Sun, much older than our Sun, but still not evolved beyond main sequence...

Alex.

Hi Alex,


in Glen's original post he mentions that PNs are the remnants of stars that have exploded, which wasn't my understanding of PN's, which I've done some reading on, but Glen is a well-seasoned Astro veteran who I had the pleasure of chatting with at Astrofest last year as we viewed a few PN's with my scope, so I figured I must have gotten my facts wrong at some point. The idea of a cold white dwarf, or "black dwarf" as they call them, is intriguing is as much as the universe allegedly hasn't been around long enough for a white dwarf to fully cool to this stage. Again, this is only what I've read. As for the stars in GC's, I'll be pleading full ignorance on these beasties.
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Old 20-05-2020, 01:08 PM
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I hadn't noticed that!

But no, not exploded stars as in super novae. A Planetary Nebula is what our Sun will produce, but won't explode. The ejection of the layers that surround the core I guess could be considered an explosion, but this is not the same thing as a star going super nova.
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Old 20-05-2020, 01:14 PM
gaseous (Patrick)
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Quote:
Originally Posted by mental4astro View Post
I hadn't noticed that!

But no, not exploded stars as in super novae. A Planetary Nebula is what our Sun will produce, but won't explode. The ejection of the layers that surround the core I guess could be considered an explosion, but this is not the same thing as a star going super nova.


Yeah, that was my understanding. Lovely sketches, by the way.
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Old 21-05-2020, 05:22 AM
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You are right, exploded is the wrong word
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Old 23-05-2020, 08:49 AM
gaseous (Patrick)
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I caught the following PN's from Glen's list when I was at Warwick in March. First time I'd seen Cleopatra's Eye (NGC 1535) - absolutely amazing under dark skies with decent aperture. You'll have to forgive my rudimentary and "low-tech" descriptions.



NGC 2867 – Mag +9.69 Planetary nebula in Carina. Quite a decent size, very bright blue-grey disk, visible without a filter. No central star visible.


NGC 1535 – Cleopatra’s Eye Mag +9.39 Planetary Nebula in Eridanus. Very bright and quite large, no filter required to view. Central star was visible, plus an outer circular shell with an additional diffuse outer nebulous halo. One of the evening’s highlights.


NGC 2392 – Eskimo Nebula Mag +9.19 Planetary Nebula in Gemini. Very bright and better viewed with no filter to better reveal the central white dwarf. There were easily visible concentric rings of nebulosity of varying densities – a very impressive PN.


NGC 2371 – Mag +11.19 Planetary Nebula in Gemini. Small but reasonably easily visible, it seems to have two lobes, separated by a darker gap.


NGC 2899 – Mag +12.19 Planetary Nebula in Vela – Diffuse but reasonable large thin grey oval cloud, shows up well with OIII.


NGC 2022 – Mag +11.69 Planetary Nebula in Orion – Small smoky disk, easily seen.


NGC 3195 – Mag +11.50 Planetary Nebula in Chamealeon – Small bright grey ball, slightly mottled appearance.
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Old 24-05-2020, 07:01 AM
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I agree with Patrick, 1535 and 2392 are great.
2371 is difficult for me.


I usually observe PN with a 12" Dob at 320 times without a filter.
With the Helix and Dumbbell I use 115x and a UHC filter.


The attached file is 70 PN sorted by surface brightness.
It is the same 70 PN as in the other lists
Attached Files
File Type: pdf PN SB 71.pdf (256.7 KB, 15 views)
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Old 24-05-2020, 07:33 AM
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This book is the PN bible

Visual Observations of Planetary Nebulae

Kent Wallace

https://www.webbdeepsky.com/publications/books/

I observed with Kent in California in 2006
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Old 24-05-2020, 08:06 AM
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Using a small 60 deg prism at the eyepiece a la Hartung helps identify smaller PN in the FOV.
The PN is seen as a point of light, field stars show small spectra.
Attached Thumbnails
Click for full-size image (100_3436.jpg)
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Old 24-05-2020, 06:34 PM
gaseous (Patrick)
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Looks like required reading Glen - I've emailed Webb Deep Sky Society to enquire about getting a copy, as they seem hard to come by. Ken, is that a DIY prism setup?
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Old 24-05-2020, 08:32 PM
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Yeah,
A film canister and a 60 deg prism.
works well.
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Old 25-05-2020, 07:27 AM
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M27

M27, the Dumbbell Nebula, NGC 6853
This PN is magnitude 7.5, diameter 8’x6’ and 1230 light years away.
Its central star is a mag 14 white dwarf.
The PN was discovered by Charles Messier using a 3.5” refractor on 12 July 1764

M27 is obvious in my 50mm finder and looks like an apple core in a telescope without a filter.
The PN is best seen with a UHC or OIII filter, its age is between 10k and 15k years

The attached image is from Aladin and the map is from SkyMapPro.
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Old 27-05-2020, 10:23 PM
gaseous (Patrick)
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Quote:
Originally Posted by glenc View Post
This book is the PN bible

Visual Observations of Planetary Nebulae

Kent Wallace

https://www.webbdeepsky.com/publications/books/

I observed with Kent in California in 2006
Ordered a copy yesterday - jeez the exchange rate and postage are killers.
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