Cygnus Loop, - a cloudy day in GIMP

[SilverAstro]

Prequeledit : Well ! this was meant to be a general question in the Astro Lounge  about the distribution of stars in the region of the Cygnus Loop with some background about why I wanted to know, not about imaging or Gimping,  but someone sometime seems to have decided it was about imaging so here we are, we got moved and we got lost and who am I to wonder

In images of the Cygnus Loop are most of the stars we see infront of or behind it ! ? How deeply buried in the milky way is it ?

I have googled and the distance to it is given as about 1500ly which doesnt seem like far so maybe most except the brightest will be behind, or on the other hand, to see most of them they must be fairly close also otherwise they would be too dim to see (image) so 50/50 or ??

Why am I asking you wonder, well today I decided to have a practice with GIMP to try to separate nebulae from stars ( if I could do that then removing pollution gradients should be easy !) The inspiration came from @Gina's post in the AS1600 topic. And so I have borrowed her image to practice on, I hope she doesn't mind :

Very difficult to keep definition in the nebula without some bleed-through of stars ! and so then I was able to colour it   red    Ha sort of

 

The result of all that being that I now wonder if I combine the two slightly displaced I could make a 3D (artificial) stereogram of it ! So do I put the stars infront  or behind, that is the dilemma ? !

 

[wimvb]

So, how did you manage to pull that of in Gimp?

If you can refine the workflow, you could put brighter stars in front of the loop, and fainter behind. That might enhance any 3D effect. (It would still be completely arbitrary, though.)

[SilverAstro]

On 28/08/2016 at 23:54, wimvb said:

So, how did you manage to pull that of in Gimp? I'm still pulling at it ! Gaussian blur, radius is the big ?mark to work on yet. and then variously 'screen' or 'addition' and/or opacity ( still trying to understand the vector space of them)

If you can refine the workflow, you could put brighter stars in front of the loop, and fainter behind. Yep, that is why I asked ! If most are one side or the other then the task is simplified if it is more like 50/50 then something sophisticated would be needed ! Yet to work on that, how to determine the brightness, size of blob? or split into those that are saturated - flat topped, and those that are not or ??

That might enhance any 3D effect. (It would still be completely arbitrary, though.) Yes, that is why I parked the question in the Astro lounge and included (artificial), not really a "proper" imaging thing nor a physics thing really   EDIT MidSep I wondered why I could not find my original topic ! Someone moved it into Beginners !! but it is not meant to be a serious beginners imaging post, totally artificial and for amusement only on a cloudy day oh and lost the two original images along the way somehow

Thanks for your thoughts, easiest if I reply in-line above !

For now I have put all the stars behind and am working on the best offset of the nebula bits for best effect, will post later if any interest.

EDIT later, or simply a crafty use of curves,, into two heaps ! looking good, might work , , ,

[Gina]

I have no objection to anyone playing with my images   Feel Free   Interesting idea you have there.

[SilverAstro]

1 minute ago, Gina said:

I have no objection to anyone playing with my images   Feel Free   Interesting idea you have there.

Thanks Gina, at the mo. I am playing with small 8bit versions (a) so as my wimpish Vista lappy doesnt seize up ! and (b) soas not to infringe your intellectual property

[SilverAstro]

Still work to be done (and it's a bit late at night !) but this is how it is looking so far. Xeye stereo cos it wont work in anaglyph, not enough colours !! One thing that would help is to split the nebula offset between the two, why did I just realize that now on posting !

[SilverAstro]

1 hour ago, wimvb said:

So, how did you manage to pull that of in Gimp?

Sorry, should have added earlier =

Basically by making a low-pass filter with a Gaussian blur to extract the low frequency components, which are predominantly the nebula, and a high-pass filter by subtraction to extract the high freq. star info. The cross-over point is the problem (familiar to builders of HiFi speakers )

[SilverAstro]

16 hours ago, SilverAstro said:

In images of the Cygnus Loop are most of the stars we see infront of or behind it ! ? How deeply buried in the milky way is it ?

To answer my own question I randomly chose some brighter and some fainter stars in CduC and they vary from from 100 to 5000ly so assuming the Loop is at about 1500ly it is in amongst them,  which makes life a bit difficult ! I wonder if I can get a Hiparchos source and filter it by distance in a Python script !

All the very faint Tycho stars had no distance.

Still, all is not lost, although we decided that a 3D representation would be artificial/arbitrary , , as an aid to visualising the Loop it is no more arbitrary than the Hubble Palette in visualising the pillars of creation , is it ? !

 

[SilverAstro]

So, after trawling through 96Gb of USB drives here is one of the missing pics. which shows the stars separated from the nebulosity.

dont know where the red coloured version went to !

BTW can anyone else see the 3d effect in the red pair, or am I fooling myself ! (should I make it more/less evident, or just give up and go back to the day job )

Now I wonder if there is a better way of separating out just the stars in Gimp , , ,