Planetary nebulae, EEVA-style

[AKB]

From last night (18-Nov-2020) as part of a local Astro club (Abingdon) Zoom observing evening:

• NGC 1514 (The Crytal Ball Nebula)
• distance estimates vary (600-900 LY?)

Conditions were terrible in terms of wind speed, and my mount (Avalon M-Uno) is known to be fairly susceptible to windy condition (due to the belt drives.)  I wouldn't normally have considered doing anything at all, were it not for the club commitment.  The star shapes are horrible with guiding at about 4" RMS.

Tony

 

[Mike JW]

On my list for tonight with the C11. Mike

and here it is from last night. Delighted to get the two small stars in the centre, the brighter inner shell and the dimmer outer shell, as well as some the darker patches.

Edited November 20, 2020 by Mike JW
added an image

[Bill S]

Abell 12  (also PK 198-06.1)

This is sometimes called The Hidden Planetary because it is almost lost within the glare of mu Orionis. 

It is the Webb Deep Sky Society's Nebula of the Month for December 2020. See this for more interesting information:

https://www.webbdeepsky.com/nebulae-clusters/2020/

It's that sphere of haze at about one o'clock under the diffraction spike.

Its visibility does depend on the sky conditions. The glare from the star can be worse with more moisture. Could be worth a look another night and may benefit from use of filters. RGB perhaps or an OIII to cut the starlight down while allowing the OIII from the planetary nebula to come through. 

A reminder. When OIII lines in spectra were first seen it was thought they could be from a new chemical element (nebulium) just like the first detection of helium was in lines in the sun's spectrum (especially at eclipse). 

https://en.wikipedia.org/wiki/Nebulium

I've included a link to another picture of Abell 12 to help you spot it in my snapshot.

http://www.caelumobservatory.com/gallery/abell12.shtml

 

 

I took 25 15 second subs but discarded the first six because of a satellite trailing across.

Regards

Bill

 

Edited December 18, 2020 by Bill S
Added Webb Soc. information.

[Mike JW]

Well done Bill, I tried a while back but failed to detect it due to poor visibility. Very helpful to have the reference image. Mike

[Martin Meredith]

Nicely caught Bill. It was clear even without the reference image, although the colour in the image from the other Bill makes me want to get the old RGB filters out for this one. Your Lodestar + reducer setup looks to be working well too.

Martin

[Mr Spock]

I'm really enjoying seeing these images. Fascinating objects.

[Bill S]

Returning to Abell 12 (The Hidden Planetary) with LRGB imaging. Pleased that this seems to be worth doing to see a bit of the colour.

 

Another interesting one which seemed to benefit from the colour treatment was NGC 2022. This is sometimes called The Watch Nebula. There's not enough magnification in my shots to show a lot of detail but it is possible to make out a hint of structure in the centre. The central star is said to be more than 120,000 K. It's 8210 light years away.

I'll post three more planetary nebula from the a couple of nights ago later.

Best regards

Bill

 

 

 

 

 

 

 

[Mike JW]

Agree, it does seem worthwhile. What is the green in Abell 12 - reflection in the scope? For this PN it would seem best to use a scope without spiders to get a less obstructed view.

With NGC 2022 you have also picked up the bright zone on the outer ring (at the bottom).

Mike

[Bill S]

A scope without a spider would help or even turning things so the spider vane wasn't on top. I noticed the green flare but did not check it out enough. The problem was that there was some movement during some of the subs, particularly the red and green ones. It was very windy. 

I've removed the worst and the result looks better. The green flare has gone and the nebula is easier to see. There's a bit of colouring of the diffractions spikes which can't be right but it's EEVA so I'll call it a result.

 

Bill

[Bill S]

Now a couple of Abell planetaries.

First Abell 24. This is very faint because it's fairly big and spread out. I really could not see anything with just the mono (i.e. L) subs and it was only when the R , G and B were added that something definitely showed up. Still pretty faint. Maybe one to come back to sometime. Astrophotographers taking much longer have come up with clearer images but that's not what I'm about. 

 

If you want something clearer how about this:

https://britastro.org/node/20299

 

Another faint challenge is Abell 21. This is also known as The Medusa Nebula. Big again and it was thought to be a supernova remnant at one time. 

Pretty faint but again the colour was necessary to make it clearly visible. The mono subs did not show it up as well. 

More information on the web. The Wikipedia article has a bit more and a clearer picture but it was a 24 inch telescope and I'll bet they spent more time on it than I did.

https://en.wikipedia.org/wiki/Medusa_Nebula

There are some useful references to Abell planetaries and large PNs and I'll be having a bit more of a look.

e.g.  https://stellar-journeys.org/abellplanetary.htm

http://www.reinervogel.net/pdf/Large_PN.pdf

The last one  I wanted to show is NGC 2371. It's also NGC 2372 because it was thought to be two separate objects. It's 4400 ly away and not as spread out as Abell 24 and 21 so shows up better.

After looking at it and noticing the shape with the apparently detached outer  lobes I found out it has the nickname The Candy Nebula. The colour is interesting but mono observing worked quite well.

 

 

This picture from a somewhat more powerful set of equipment shows it a bit more clearly.

https://subarutelescope.org/en/gallery/pressrelease/2003/07/01/2180.html

All these snapshots needed some wind spoiled subs removing which is why the numbers of R, G and B don't match.

Best regards

Bill

 

 

 

 

 

 

 

 

[Martin Meredith]

Lovely captures Bill. Now that we are definitely not in summer I really must get back to PNs...

As you're finding, this is one area where colour helps a lot in detecting these elusive objects in the first place -- though some of the Abells are so faint nothing much is going to help except more exposure time. Colour also shows up any problem subs nicely... Its interesting to switch off hot pixel removal ans see how ugly the result is.

Work-flow wise, are you starting with RGB then adding L, or starting in L and then adding RGB (then more L perhaps?). 

Martin

[Bill S]

Martin - My work-flow has been to do the Ls first and then R, G  and B in that order. So, I get a bit of thrill when the first B goes in and the stack miraculously becomes colour. I sometimes add a few more subs of various types if the stack is too faint to see what I'm looking for. 

I've ordered a clear (but hopefully parfocal) filter to try instead of the L filter to see if I capture a few more photons as I think you suggested in another post. Have you any suggestions for work-flow and relative numbers of LRGB? There's probably some guidance from astrophotographers but I have not been paying much attention. I've got a hydrogen alpha and an oxygen III filter I have not tried yet for multispectral EEVA but they'll be a bit more tricky since they are probably not parfocal with the LRGB set (one of them is an Astronomik rather than a Baader). I do have the luxury of an electric focuser so I should be able get good enough reproducible offsets to cope. It's all getting a bit more complicated than I'd like, though.

Bill

 

[Martin Meredith]

Agreed, seeing the first of the complete set of LRGB is always exciting. My approach depends on what I'm viewing. If I expect to be looking at objects in colour (typically GC, OC or PNs) then I'll do something like 4 each of RGB then L. If I'm looking at a galaxy or group of galaxies I'll typically start off in L and if the galaxy looks like it might be interesting in colour, I'll add RGB as an afterthought. You can add in any order so topping up poor subs is easy enough. What is quite surprising to me is how little colour is needed to produce 'decent' colourised images (particular for bright objects like open clusters). Faint PNs like your Abells do need lots of colour though.

What actually happens in my case is that if I select LRGB, the software will collect data in the order BGRL. The rationale is that in the case of multiple filters, they are best ordered by increasing transmissivity so that when the threshold for star detection is computed on the first sub, it is more or less guaranteed to be sufficient for star detection on subsequent filters. If you find yourself having star detection issues I suggest starting with B. This is going to be particularly important if you are planning to combine narrowband with L - start with Ha or Oiii.

On the narrowband front, I hope to implement special processing fairly soon for this scenario. The idea is that if the software detects L + 1 narrowband filter, it will map the narrowband to, say, red, and overlay it on the L, with the saturation slider controlling the blending. I still need to think about the best approach when it detects multiple narrowband filters. Watch this space!

The C filter is useful for extracting more photons relative to L,  particularly in the IR part of the spectrum where galaxies are emitting quite strongly. One day I will do a proper test to see what difference it makes.

Martin

 

 

[Martin Meredith]

Luminosity plus narrowband is now integrated  into Jocular as a separate mode. You would collect L + Ha, say (or L + OIII, or whatever) and engage the L+ mode which maps the narrowband data to a separate layer. The saturation control then manages the amount of blending. I want to do some testing myself as I don't have any narrowband + L FITs to demonstrate it with (most of my narrowband EAA took place before I made a habit of saving FITs), but if anyone does wish to test I'm happy to send the updated code.

This gif that I made years ago with SLL shows the kind of effect that will be possible. In this case it is an on-off animation but in the tool the blend is gradual. 

Martin

 

[Bill S]

I like the look of that.

It could be very useful for highlighting star forming regions etc. 

[Mike JW]

I agree with Bill; adds another layer of observational detail.

[callump]

A return to Abell 12 - last night started reasonably nice and deteriorated as it wore on, so I only got a few targets. This was taken late on as the freezing fog was developing.

I'm not sure where the big spike is coming from - maybe I need to have a go at collimating the C11.

It's a pity the spike goes straight through the nebula, but does also add a little bit of interest!

Callum

[Mike JW]

Hi Callum, that came out well.

Spike on a SCT - interesting one. I do check my C11 collimation every now and then, preferably on a moonlit night so as to not waste decent observing time.

Mike

[callump]

2 hours ago, Mike JW said:

I do check my C11 collimation every now and then, preferably on a moonlit night so as to not waste decent observing time.

I have a few maintenance chores I need to do like collimation and redo polar alignment. Even a clear view of the north with the Moon up would be good 🙂 

I was wondering if the spike was caused by the dew shield, but did not follow it up at the time.

Callum

Edited January 7, 2021 by callump

[Mike JW]

At last I have been able to point the 15 at Abell 12. (I remember the struggles I had seeing it with the 20" Dob visually - now so easy using EEVA technique). Three different stretches applied.

Mike

 

 

[Mike JW]

Earlier on in this post Callum's post for NGC 1514 inspired me to take a look with my C11. Last night I had a chance to point the 15 at this PN.

Using the 15 has  produced a shot with better detail - evidence of the different shells and better definition of the darker regions. I had to dump quite a few subs as they came in due to sky conditions  being  unsteady.

Mike

[Mike JW]

Abell 13 - when I pointed the C11/ultrastar at this PN last night I knew nothing about. It took a little while to be sure I was in the right area.  I decided to stack as I went and all I could see was NOTHING. A rethink required. I played with different stretches until at last I thought I had a hint of something. Drastic measures required - I decided to abandon my personal 5 minute rule, set the camera running and went indoors to warm up (gear was sparkling in the frost). Success.

Abell 13 is seriously faint (different magnitudes given from mag 15 to mag 18), secondly it emits very little in the green spectrum which means visually it is impossible - read a report of someone using a 27" scope, with O111 filter and maybe got a hint - but not definite. It lies about 3,900lyrs away.

I have attached a gif file so you can see the image build up. If I reduce the noise too much, then I loose the PN.

It was effort to set up the gear last night but to get this result - worth the cold. The dark circle in the PN is an annoying dust bunny. Also just to the left of the obvious bright star near the centre is a faint dot which I think might be the CS.

Chaps with colour set up - you might do better than this mono attempt - have fun.

Mike

[Martin Meredith]

Definitely a tough one, like many of the larger Abells. I'll have a go in colour but if it is hard to see in mono I doubt I'll be able to make much of an impression, but I ought to try with an OIII filter. This one needs a 48" and old-fashioned film photography, obviously...

Martin

[icpn]

no point in trying with an OIII filter Martin as there is practically no OIII emission. The only filter that might help would be an H-ALpha one.

 

Owen

 

[Mike JW]

5/02/21 - One of those short unexpected gaps came through in the early evening and the skies were good. I decided to have a mainly PN session.

First up is Abell 10 in Orion. This was easy to pick out form the background stars and in the close up the CS is visible with hints of structure.

 

The rest of the session was spent in Gemini.

Abell 19 - is in the exact centre of this shot and yes you are right - there is NOTHING showing up.  I tried all the different stretches. Presumably this PN emits very little light in the green part of the spectrum . It is mag 16/17, and is about 7500 lyrs away.

Abell 21 - The Medusa (yet another shot of this delightful PN, lurking about 1500 lyrs away.

NGC 2392 - Eskimo Nebula. The close up shows its double shell and hints of structure.  6500 ish lyrs away and about 10,000 yrs old.

This is the best shot I have ever been able to achieve.

 

NGC 2371 lies about 4,300 lyrs away and is bi-polar. 

HDW - 6 is about 1050 lyrs away. Look closely and you will see a circle indicating where it is, near the centre of the FOV - NOTHING seen!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

M 1-7 is a compact bright PN about 8000 lyrs away.

 

Abell 14 in Orion ( and from a few nights back). Tricky to get this one, ( I have played about in photoshop to enhance it a bit).

 

Mike

Edited February 17, 2021 by Mike JW