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steppenwolf

M27 The Dumbbell Nebula in bi-colour

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22 hours ago, steppenwolf said:

They will be cutting NII from the planetary core for certain but perhaps not from the halo.

Thanks to @Mick J who has carried out some research, it would appear that there is a lot of worthwhile NII in the outer halo. Now, how do I explain to my wife, Janie, that the Astrodon filter collection that I currently have is not quite complete? :icon_biggrin:

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On 9/7/2017 at 11:28, steppenwolf said:

Thanks to @Mick J who has carried out some research, it would appear that there is a lot of worthwhile NII in the outer halo. Now, how do I explain to my wife, Janie, that the Astrodon filter collection that I currently have is not quite complete? :icon_biggrin:

OK, so I take the blame for this  :icon_biggrin::icon_biggrin:   sorry Janie.

The more I look at pictures of this nebula on the net the more complicated and varied it seems to get - let me add a disclaimer in here: I am no imager and have no understanding of processing, I do like a nice deep space picture and enjoy seeing the technology for acquiring them advancing.  So pleased I don't have to buy filters and stuff.

Just came across this page on the astrodonimaging site,  Don Goldman's  M27 in a Different Light NII.  I guess some of you may have seen it before, taken in 2008.  Don is convinced the outer shell is NII, the interesting fact (new for me) is that the wider Ha filters (above 5nm) pass the NII wavelength, with Ha 3nm & NII 3nm a small overlap occurs but the emissions are different.

I am cluttering up this thread enough, time for bed.

Edited by Mick J
changed 7nm to 5nm
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9 hours ago, Mick J said:

I am cluttering up this thread enough, time for bed.

Not at all, this provides much food for thought!

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On 06/09/2017 at 10:55, gorann said:

I love them all four! Why not try a 50:50 blend of the two bi-colour versions? (or use layer masks and the brush tool and use the best parts out of each version)

Just for you @gorann, here is a different blend of the two :icon_biggrin:

59b24df978bf9_M27_RGB_version3_combined.thumb.png.a37906313d6edac26857ba547760826d.png

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1 hour ago, gorann said:

Thanks Steve, I am humbled

And it looks great!

One of the joys of narrowband - there is no defined palette, anything goes! I actually prefer the blues and reds in this object as they more closely resemble a broadband interpretation.

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Yes, you made it look quite RGBish. Maybe the red is a little bit too rusty for my taste but then that is just me. Maybe something like this even looks more like a broadband image. Maybe I went over the top. Many maybes and sorry for messing with your superb image.

EDIT: I see after uploading that I could have used layers to protect the background stars from getting too red.

M27_RGB_version3_combined GN.png

Edited by gorann

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8 hours ago, gorann said:

Many maybes and sorry for messing with your superb image.

Feel free to play!

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Just to quickly come in on this thread, I've found several targets with significant [NII] emission, to the point that I use that filter a lot more than [SII].

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The NII (6584A) emission is more pronounced in PN nebula - driven by the central star.

In SNR the SII and OI lines are more intense than in PN.

(Richard Walker's recent "Spectroscopic Atlas", Cambridge, tells the whole story)

 

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I've recently been imaging parts of the Cygnus Loop. It's a SNR but I think the emission is from the shock front.

In my trial subs I've been seeing almost as much [NII] as HII, with [OIII] much weaker, and [SII] barely visible.

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I was expecting NII in the core region of a PN but hadn't expected to see so much in that outer halo.

I have no real desire to get a really narrow SII filter but this little experiment has made me wonder about an NII. I always knew that PNs would suffer some detail loss by the use of such a narrow Ha filter but I'm surprised just how much. However, the loss will be significantly less in non-PN nebulae.

Just love these new knowledge gathering sessions but my wallet ain't so sure ......

I might experiment with using my 7nm Ha filter and seeing if I can extract the NII from that data!

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When I was ordering my Astrodons, Ian King persuaded me to go for the (cheaper!!) 5nm Ha & SII & 3nm OIII for pretty much these reasons. Although I do love those tight wee stars I see with the Ha 3nm. Be nice to complete the collection tho.. you know you want to... ?... then of course there's the bigger FW you'll want to add so there's no faffing around swapping filters ?

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On 10/09/2017 at 11:54, Sp@ce_d said:

Be nice to complete the collection tho.. you know you want to... ?... then of course there's the bigger FW you'll want to add so there's no faffing around swapping filters ?

Yes, I received the same initial advice but I decided that the 3nm Ha was what I really wanted having already got a 7nm Ha filter, 5nm seemed just a little too close! I have no regrets with my choice as I love the Ha 'clarity' and small stars. SII has never floated my boat but NII in its own right just might!

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On 10/09/2017 at 19:40, mike005 said:

Wonderful image and an interesting write-up; thanks for sharing.

Thank you, Mike

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Hi Steve

A quick question about the processing - if you're prepared to reveal some of your secrets that is....  

I have had a go at emulating this image (blatant copying, in fact) using my Esprit 120/QSI690 combo.  I have nowhere near as many subs as yourself - only 3hrs 40 mins each of Ha and OIII.  I put it together quickly this morning - just to check on progress - and it seems that no matter what I do the OIII absolutely swamps the Ha.  Did you find this?  Is that why you shot nearly twice as much Ha as OIII (or would that make no difference)?

Steve 

Edited by gnomus

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As a non-imager all these look pretty amazing to me. There's so much more going on than the fuzzy grey blob I'm used to :tongue2:

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9 minutes ago, gnomus said:

A quick question about the processing - if you're prepared to reveal some of your secrets that is....  

Happy to oblige, Steve :icon_biggrin:.

Yes, the OIII is very strong with this one (I've heard that somewhere before....) and you are right, it does swamp the Ha so I gave greater boost to the Ha data to partially compensate. It is just lack of good sky conditions that prevented me from matching the sub-frame count, I don't quite trust even 3nm OIII with the Moon about!

The Ha outer halo is there but quite faint so I had to work on that quite hard using a technique called 'screen mask invert'. This technique is an enhancement by Scott Rosen of a process originally created by Jerry Lodriguss and in essence, it brightens faint regions of an image while leaving core details untouched. Here is a summary of the process but it is a PhotoShop routine rather than a PI one so it may not be of much use to you:-

1. Copy the image to the clipboard and past it as a new layer on top

2. Produce a Layer Mask  - 'Reveal all' and name it 'Screen'

3. Alt click on the mask to select it, paste the contents of the clipboard into the mask and invert it.

4. Select the image icon in Layers then right click on the mask and select 'disable'

5. Blur the image using Filter - Noise - Dust and Scratches until the star just disappear but try not to go further than 15 with the radius, leaving threshold at zero

6. Change the blend mode of the top layer to Screen. The image will brighten noticeably

7. Re-enable the mask by right clicking on it and selecting 'enable' and Alt click on it

8. Pull in the white and black levels to give a contrasty inverted view

9. Create a Levels adjustment layer and bring in the black point until the background sky level matches the original image before any of this took place

10. Create a new layers group and drag the Levels adjustment and mask layers into the group so that you can easily toggle your work on and off to help with 9 above

11. To repair the core which will be too bright now, lasso the core with a 50 pixel feather and save the selection, then.....

12. Alt click on the mask again and paint all over the core with a black brush with an opacity of 50% to restore the core to its original brightness

Et voila - fainter bits lifted, core protected. That's a page in my new book that I don't have to write now! :evil4::icon_biggrin:

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35 minutes ago, Mr Spock said:

There's so much more going on than the fuzzy grey blob I'm used to :tongue2:

I guess, Michael, that that is why I image much more than I observe but there is still something a bit special about chasing down a dim fuzzy! Funnily enough, this object was the first one I tracked down with my first telescope, a Meade 4.5" Bird-Jones reflector - I was blown away by this first encounter.

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Thanks Steve

I'll give it a go.  

9 hours ago, steppenwolf said:

.... but it is a PhotoShop routine rather than a PI one so it may not be of much use to you:-

....

Not sure why you have me down as a PI Puritan.  I'm really quite offended !!! :evil4:  

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11 hours ago, steppenwolf said:

Happy to oblige, Steve :icon_biggrin:.

Yes, the OIII is very strong with this one (I've heard that somewhere before....) and you are right, it does swamp the Ha so I gave greater boost to the Ha data to partially compensate. It is just lack of good sky conditions that prevented me from matching the sub-frame count, I don't quite trust even 3nm OIII with the Moon about!

The Ha outer halo is there but quite faint so I had to work on that quite hard using a technique called 'screen mask invert'. This technique is an enhancement by Scott Rosen of a process originally created by Jerry Lodriguss and in essence, it brightens faint regions of an image while leaving core details untouched. Here is a summary of the process but it is a PhotoShop routine rather than a PI one so it may not be of much use to you:-

1. Copy the image to the clipboard and past it as a new layer on top

2. Produce a Layer Mask  - 'Reveal all' and name it 'Screen'

3. Alt click on the mask to select it, paste the contents of the clipboard into the mask and invert it.

4. Select the image icon in Layers then right click on the mask and select 'disable'

5. Blur the image using Filter - Noise - Dust and Scratches until the star just disappear but try not to go further than 15 with the radius, leaving threshold at zero

6. Change the blend mode of the top layer to Screen. The image will brighten noticeably

7. Re-enable the mask by right clicking on it and selecting 'enable' and Alt click on it

8. Pull in the white and black levels to give a contrasty inverted view

9. Create a Levels adjustment layer and bring in the black point until the background sky level matches the original image before any of this took place

10. Create a new layers group and drag the Levels adjustment and mask layers into the group so that you can easily toggle your work on and off to help with 9 above

11. To repair the core which will be too bright now, lasso the core with a 50 pixel feather and save the selection, then.....

12. Alt click on the mask again and paint all over the core with a black brush with an opacity of 50% to restore the core to its original brightness

Et voila - fainter bits lifted, core protected. That's a page in my new book that I don't have to write now! :evil4::icon_biggrin:

Jings - it works.  

Will you damn well hurry up and finish that book, Steve?  We lesser mortals need all the help we can get!

Thanks again.

Edited by gnomus

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53 minutes ago, gnomus said:

Jings - it works.  

Will you damn well hurry up and finish that book, Steve?  We lesser mortals need all the help we can get!

Thanks again.

I'm over half way there now, Steve, early next year I hope!

3 hours ago, gnomus said:

Not sure why you have me down as a PI Puritan.  I'm really quite offended !!! :evil4:  

Ooooops ....:icon_biggrin:

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