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Planetary nebulae, EEVA-style


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I'm starting this thread to encourage posting of short-exposure images of planetary nebulae. Apart from the obvious suspects, M27, M57 etc, I generally haven't had a lot of success (and have ther

From the same session, this is NGC 6445, a mag 13.2 PN, also in Sagittarius, this time with a surface brightness of 22.0. This 'wide' field shot shows the object, just over half an arc-minute in

Thanks Chris for that link.  Here's most of the rest that I observed over 2 nights this week. They consist of 8 of the 11 NGC PNs in Aquila (turns out I didn't manage to get 2 of them in the fram

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Hi, Callum/Martin,

Just had to give NGC 7094 a look with the 15/ultrastar. I was pleased to get some detail but it took much fiddling around with the settings. I did enhance the shot in photoshop.

Now for some interesting info. Apparently the CS (mag 13.7) is of a rare type (hybrid PG 1159 star - failed to work out what this means). In essence it is in transition to becoming a fully formed white dwarf. It pulsates gently - slowly and by small amounts. This would appear to reflect the stars composition as it completes the transition. One article says it is hydrogen deficient but another article writes about the high levels of hydrogen still remaining in the stars envelope, along with C 1V (ionised carbon).

The internal zone around the CS is being blasted by the very energetic winds and is part of the cause of the filament patterns high resolution images reveal.

One article suggested that the cause of the filaments/pattern is due to the original star being a triple  star.

The PN is 5000 lyrs away, about 3 lyrs across and old in PN terms.

Mike

1859879557_NGC709412Sep20_11_55_20adjusted.jpg.49304a28e228dca4c0cecd281f695cb1.jpg

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On 11/09/2020 at 18:44, Martin Meredith said:

Great result Callum. I observed this one too a few nights back in LRGB. This is a 7m15 stack. The central star appears really blue -- I guess this is the result of absorption by the nebula.

I tried to orient mine to match yours but I think yours is flipped relative to mine. There's a bonus mag 16.3 galaxy in the shot at my 11 o'clock, your 4 o'clock.

Did you combine L with RGB or is it pure RGB?

Martin

1998276697_Screenshot2020-09-11at18_43_55.png.b5943c1b0f577b134d452c6d40e5f746.png

I love the contrast of the blue star. Great capture both of you.

M

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  • 2 weeks later...

I was heading to Abell 46 in lyra but first decided to sync on M57. Noting I was using the 15, I decided to do what I think will be my last ever camera look at M57 and here it is - rather pleased with the detail.

First up - the context view. The key is short subs. View is a stack of 34 x 2 sec subs. If you know where to look the galaxy IC 1296 is starting to show up but the aim of this was to capture M57 in as much detail as possible. Recently I realised that actually I know very little about M57 so at the end of the post is a few summary details - apologies to those who have far more knowledge than myself.

541003897_M5721Sep20_08_33_37.thumb.jpg.87efbfd4d2edb77404210c940fcf9f7f.jpg

Delighted to get the little extension to the ring, top left, and hints of other extensions bottom right quadrant. I was not expecting the two stars to shine through the ring at the top. Great to see some of the structure appearing as well.

1903280105_M5721Sep20_08_32_00.jpg.f87f10889e37f94b824836b49f387daf.jpg

The other week I was wondering what M57 would look like in 3D. I was totally unprepared for a 'tilted slightly elongated football' inner cylinder of hot principally ionised Helium, surrounded by a doughnut shaped ring of expanding ionised gas.  The outer ring contains ionised nitrogen and oxygen (O111) which make up the characteristic red and green colours. Other atoms of note are flourine, neon, sulphur, argon and chlorine. The orientation of M57 is toward planet earth and thus we see a ring with a central cavity - we look straight down the central cavity. In my naivety I had not picked up that beyond the ring that we see in visible light is yet more gas that has now cooled and expanded to low densities. 

Its distance from us has been a matter of discussion and currently has settled to 2300 lyrs away and getting less as M57 is heading towards us at 21km/sec. The ring is expanding at about 20-30km/sec. 

https://www.spacetelescope.org/videos/heic1310e/ - well worth a look.

Next post will be Abell 46 - the real aim of this Lyra jaunt.

Mike

 

 

Edited by Mike JW
factual mistake
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I tried to find Jones 1 in Pegasus a couple of weeks back without success. I persisted with locating it last night, but even with 30s exposures there was just a hint of it 'live' on screen.

Registered and stacked it is a bit more obvious in this result. It was toward the end of last nights session and the sky was deteriorating - will try again if/when we get a better night...

Jones1_2020920_800_annot.jpg.bdf06429da5005d1a28d99ea05eaf3c6.jpg

 

James 1 was discovered in 1941 by Rebecca Jones at Harvard. 

Callum

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That's about as good or better than I've ever managed to see Jones 1. I just spotted that you're operating at f6.3 -- impressive.

I tried it in LRGB recently and found a distinct electric blue/green with the saturation turned all the way up. No idea if this is genuine or not.... Interesting to see there is a very blue star in the middle -- I wonder if this is the central star. It certainly looks quite central and distinct in hue from the rest of the grouplet. This is 8m 20s.

182563643_Screenshot2020-09-21at20_21_10.png.6d072160c0aa2d98e08e78b597df16d2.png

I see to recall there is another Jones PN, or maybe one that is similarly named. I have a JnEr 1 in Lynx listed.

Martin

 

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Hi Martin,

internet images show the nebula as mostly blue - i guess it is fairly old.

Your blue central star looks like a good candidate for the central star!

There is a PN Jones-Emberson 1  which is in Lynx - looks like a good target too, when it comes round.

Callum

 

 

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Nice capture, Mike. Very smooth against the background.

Looking more into Jones 1, there's a good shot of it here: http://helixgate.net/jones1.html

Apparently, the blue central star is mag 16.0 (GAIA green filter) and has a B-V (or rather GAIA b - GAIA g) of -0.25, making it very blue indeed (other estimates give a B-V of -0.1).

Jn 1 or Jones 1 doesn't turn up anything on Simbad but PK104-29.1 does the trick.

Martin

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Your (Callum) post of Jones 1 reminded me it was something I'd look at last year. Here's a rather noisy stretched image. I notice I have some rather square stars reminiscent of what I used to get with the Watec.

800979037_Jn1(Jones1)23Sep20_00_27_25.jpg.4fd23158da2d8ebea596ce59e5eb5c73.jpg

 

Cheers

Bill

 

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Abell 46 in Lyra.

This a challenge even for the Dob. I kept the subs short as conditions were unsteady and it seems to give sharper stars.

The central star is an eclipsing binary and angled to earth such that it is viewed (spectroscopically) as a grazing eclipse. It is thought that the two stars lie within a common envelope and it is likely that the bigger star has expanded to encompass the orbiting companion. In reality this PN is a hollow tube.

Mike

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That's a tough one (typical of the Abell PNs!). Interesting to read about the central star. Apparently it has a period of just under 12 hours and varies in the brightness by 1.5 mags in that time if I've read it correctly. Depending on the shape of the light curve you might be able to catch some of this variation in a typical EAA session.

My eye is also drawn to that lovely curved 'thing' just to the right in the eyepiece view. Looking it up it appears to be a chance alignment of some stars with a mag 17.8 galaxy (PGC 1793463... the longer the number, the more recently catalogued I imagine). This is estimated to be 999 million light years away, so quite a range of distance in this image. 

Martin

 

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Here is another PN - NGC 6058 in Hercules. Now this one gets really interesting.

At first glance it has the normal ring appearance with a central star. No change in my close up but start reading up..... - https://www.astrobin.com/jcjxss/D/?nc=user

It is multi polar. There were 3 bi-polar outburst roughly in the same plane. Then awhile later there was fourth outburst more or less perpendicular to the other three. This last one is slightly elliptical and is now interacting with the other three. Looking closely at my shot and comparing to the web site link above it would appear that I have imaged the last outburst.

https://www.researchgate.net/publication/258841668_Multiple_outflows_in_the_planetary_nebula_NGC_6058

I wonder if I would get anymore detail if did 1x1 subs and ran it with the 15 for much longer?

Mike

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218889371_NGC605820Sep20_10_52_14.jpg.0124f49045e7e626d80454e2fa7acb5e.jpg

Edited by Mike JW
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  • 3 weeks later...
On 27/08/2020 at 09:05, Martin Meredith said:

With some PNs I've had more success with linear 'stretch' ie no stretch. I've a feeling we need an anti-stretch

Wondering if this is an occasion to consider equi-population binning (ie. histogram percentiles) to tease out some subtle variations?  I used to use this quite often as initial processing step, and then indeed sometimes apply an ‘anti-stretch’, for some targets... easy to automate with few parameters ;)

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Good ideas, and in general there are all sorts of highly non-monotonic techniques that could be included to bring out faint detail. I included an implementation of CLAHE (contrast limited adaptive histogram equalisation) in a much earlier version (never released) but perhaps it is time to reinclude it.

It is quite easy to add this via the adaptive_histogram method here:

https://scikit-image.org/docs/0.15.x/api/skimage.exposure.html

 

As for anti-stretch, changing the gamma function to include exponents > 1 is one way to go.

Martin

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  • 4 weeks later...

NGC 1514 The Crystal Ball Nebula

This object was discovered by William Herschel on 13 November 1790 and so it will soon be its 'birthday'. Herschel had thought that all nebulae were unresolved distant masses of stars but this one led him to think some might be glowing gas. The origin of the nebula is a binary system and the star visible at the centre of the nebula is not the white dwarf that threw off the shell to give the nebula it's the giant type A star.

The distances to planetary nebulae are often rather uncertain and I've read values of 600 to 2600 light years.

The nebula is nicely set off by two bright field stars. I think they are guardians...

And what is more there are even some diffraction spikes on the the bright central star.

I will return to this (and several other PNs) when I've got the multi-spectral features of the latest version of Jocular and my filter wheel up and running.

There are many interesting articles about this object. This one has some interesting diagrams about its structure and appearance.

https://iopscience.iop.org/article/10.1088/0004-6256/140/6/1882/pdf

Happy viewing.

Bill S

722105482_NGC151411Nov20_14_59_34.jpg.793fad526487255afb223575c167262f.jpg

 

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Hi Bill,

The image has fired me up for a visit sometime. Apparently the orbit of the companion is very eccentric and takes about nine years to complete one orbit. This is the longest known orbital period for a PN and confirms that long orbital period binaries can form PNs. One article back in 2003 thought the orbital period was just 10 days.

Below is the WISE image.

Mike

wise-galaxy.jpg

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Another planetary nebula from a few nights back was NGC 2371/2372. There are two definite lobes to this and although there is only one planetary nebula it was catalogued by Dreyer in the New General Catalogue as two objects. This was carrying on the description as two objects (Class II: faint nebulae) by William Herschel according to Mark Bratton discussing it in The Complete Guide to the Herschel Objects.

There are two faint lobes at right angles to the brighter lobes. These are further out and just visible in my stretched snapshot. As usual for PNs the distance is a bit uncertain 1600 to 5000 ly. The nebula is mag 13 and the central star is mag 15.

1745922935_NGC237112Nov20_23_38_52.jpg.7835d7106214f947b7d5f6ae2c4a138b.jpg

 

Another one I'll come back to for another look.

Bill

 

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