Author Topic: New Tutorial: M27. Revealing external faint halo  (Read 39435 times)

Offline Silvercup

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Hi All:

I just wrote my first tutorial:  M27. Revealing external faint halo from an underexposed H-Alpha integration.

In this document I describe a processing workflow that focuses on enhance faint details on underexposed images using AtrousWaveletTransformation and PixelMath. We also describe using of StarMask, Deconvolution, noise reduction with ATrousWaveletTransform and MorphologicalTransformation.

For this example we have used an image of M27 acquired by Dave Halliday with a Vixen Visac at f/9. It's an integration of 25 frames of 420 seconds in the H-Alpha emmision with an ST-2000XM 2x binned. The image has an initial Histogram strech. Despite of short subexposures we are able to reveal external faint halo.

Thanks to Dave for letting me use his image.

I hope you found it usefull.

http://www.aacadiz.com/zona_trabajo/tutorials/m27/en/m27procexample.html

Best Silvercup.

P.D. Mañana lo subo en catellano. Un saludo.

Offline sleshin

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #1 on: 2010 May 02 15:53:43 »
Very well done. Thanks for doing it.

Steve
Steve Leshin

Stargazer Observatory
Sedona, Arizona

Offline Niall Saunders

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #2 on: 2010 May 02 17:03:04 »
Well done Silvercup,

This is an excellent tutorial that demonstrates how well PixInsight can extract high quality information from what initially appears to be sub-optimal data (no offence Dave ;)).

It also demonstrates that the extraction of that data is NOT a trivial sequence of steps. Each step needs to be understood and the processes required to achieve that step need to be fine tuned given the data that is being manipulated.

What is definitely shows is that PixInsight CAN be used to extract the information WITHOUT having to resort to 'airbrushing' (sorry to throw this into the discussion Bud, but you can see where Juan is coming from when you see an image being processed this way, as opposed to the 'user-defined' or 'manual' approach currently needed in the likes of PhotoShop).

Of course, what it also MOST DEFINITELY shows, is that Silvercup has rapidly risen to 'PI-Jedi' status, not only for creating such a stunning transformation to Dave's original data, but also for being able to put together such a clear and useful tutorial to help others try to achieve similar results.

Well done indeed.
Cheers,
Niall Saunders
Clinterty Observatories
Aberdeen, UK

Altair Astro GSO 10" f/8 Ritchey Chrétien CF OTA on EQ8 mount with homebrew 3D Balance and Pier
Moonfish ED80 APO & Celestron Omni XLT 120
QHY10 CCD & QHY5L-II Colour
9mm TS-OAG and Meade DSI-IIC

Offline budguinn

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #3 on: 2010 May 02 17:47:38 »
Silvercup,

This looks like a great tutorial.....I have a few hours of time on this object with my QSI and FRC300 that I have never processed.....this will be a great tutorial for learning the included processes......thanks for taking the time to make it.....I'll give it a try in the next few days.

best regards,

bud guinn
http://www.budguinn.com


Offline dhalliday

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #4 on: 2010 May 02 18:15:02 »
Silvercup
Boy that was some bit of work..!!
I got a bit dizzy trying to understand it all... >:D

The pragmatist in me can't help wondering if just switching to f/6.4 is easier...(!!)
I also wonder how much damage the moon being out does...(plus my bad LP...)
The Goldman image is what I am shooting for..(in HaRGB..)...eventually.
But it seems I will not get there,even with EXPERT processing,if I don't change the imaging plan..
By the way..were you working off the tif stack..?
I forget if I sent it...
Again,many thanks...I have a lot to learn !

Dave
Dave Halliday
8" Newtonian/Vixen VC200L/ TV 101,etc etc
SSAG/EQ6
CGE Pro
SBIG ST2K,ST10XME

Offline Harry page

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #5 on: 2010 May 03 06:31:43 »
Hi

Would like to look but the link seems to be broken  :'(


Harry
Harry Page

Offline Juan Conejero

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #6 on: 2010 May 03 06:48:50 »
My heart is still bumping. For one moment, I thought somebody had hijacked our website! ;D

Excellent work, Silver. A really nice tutorial. To both you and Dave: Can we use your text and images to include this as an official tutorial on PI's website?
« Last Edit: 2010 May 03 06:56:41 by Juan Conejero »
Juan Conejero
PixInsight Development Team
http://pixinsight.com/

Offline Silvercup

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #7 on: 2010 May 03 07:11:43 »
Hi All:

Harry our server is down.

Juan, It was more easy to clone PixInsight tutorial than make one from zero. You can add to tutorial sections if you consider that I haven't made any dumb thing. I will be very glad.

Dave:

If you shoot at f/6.4 is easier to guide and capture more light and more field.

The moon should not be an inconvenience to capture in H-Alpha, the moon and this filter works very well, I do not appreciate image gradients. Obviously no moon is much better. However, in OIII moonless shoot is a must.

Don Goldman's image is made with two emission H-Alpha and OIII. I don't know how he mixed to obtain the image in RGB (well, I imagine). What I can see is that the red channel does not correspond exactly with the H-Alpha emission . The image has a lot OIII and therein lies the difference.

Here is a comparison of M27 with different filters:

http://dg-imaging.astrodon.com/gallery/display.cfm?imgID=148

As for changing the imaging plan, triy to get OIII on a moonless night and longer exposures to 20 minutes, with the new mount you should have no problems. Take three or four more 20 minutes exposures of H-Alpha.

Your image has H-Alpha and is similar to Robert Glender's one at this link:

http://apod.nasa.gov/apod/ap030725.html

Best, Silvercup.

Offline Niall Saunders

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #8 on: 2010 May 03 08:45:50 »
Quote
My heart is still bumping. For one moment, I thought somebody had hijacked our website!

That said Juan, it is a clever way to avoid having to sit down and actually 'learn' how to put together a web page.

I seem to remember that, not so long ago, 'someone' did something very similar when they were trying to figure out how to put together a PJSR script O:)

Cheers,
Cheers,
Niall Saunders
Clinterty Observatories
Aberdeen, UK

Altair Astro GSO 10" f/8 Ritchey Chrétien CF OTA on EQ8 mount with homebrew 3D Balance and Pier
Moonfish ED80 APO & Celestron Omni XLT 120
QHY10 CCD & QHY5L-II Colour
9mm TS-OAG and Meade DSI-IIC

Offline Harry page

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #9 on: 2010 May 03 08:56:34 »
Hi

Looks excellent  ;) Just what people need when they get past my basics  ???

I will goo and read it again  8)

Harry
Harry Page

Offline Carlos Milovic

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #10 on: 2010 May 03 10:19:41 »
Very nice :) thanks for sharing, and your hard work on it!
Regards,

Carlos Milovic F.
--------------------------------
PixInsight Project Developer
http://www.pixinsight.com

Offline dhalliday

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #11 on: 2010 May 03 13:32:05 »
Silvercup/group
I certainly have no objection to any use of the image.
PM me if you need the Tif stack (out of DSS...)

That link to the Goldman site is most excellent..!
I was talking with N Fleming about how he sometimes use just the two strongest NB channels,and uses a "blend" of the two to make up the third channel.
M97 for example is ALL Ha and OIII...
Sort of OT here...but in P math ( >:D) do two images have to be the same format (ie 32 bit tifs,etc) to do stuff..??
My P math is "not working"..when I try blending ("red" + .4Ha...)..
for example...

They are not identical images either (FOV wise)...but I believe they are registered.

Dave
Dave Halliday
8" Newtonian/Vixen VC200L/ TV 101,etc etc
SSAG/EQ6
CGE Pro
SBIG ST2K,ST10XME

Offline Maxi

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #12 on: 2010 May 04 03:11:10 »
Gracias Silver, ese tutorial puede ser muy interesante, para esos halos de los objetos que se intullen pero que cuestan un HUEV... sacarlos sin llenar la toma de artefactos.

Por cierto lo has sacado en castellano, o no lo he sabido ver  ^-^

Saludos, Maxi

Offline dhalliday

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #13 on: 2010 May 04 03:36:16 »
PS
It would appear that most of the outer stuff is OIII... >:D
Based on last nites images...
Again SII is a blank.
Need help using Pixel math the create a third channel out of ? the Ha AND the OIII... :'(
I will post later...

Dave
Dave Halliday
8" Newtonian/Vixen VC200L/ TV 101,etc etc
SSAG/EQ6
CGE Pro
SBIG ST2K,ST10XME

Offline Silvercup

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Re: New Tutorial: M27. Revealing external faint halo
« Reply #14 on: 2010 May 04 07:19:20 »
Hola Maxi:

El tutorial tiene como objetivo precisamente eso. Recientemente pude reprocesar una toma de M81-M82 en la que su autor afirmaba que no había ni rastro de IFN y mediante este procedimiento la logre sacar, muy débil, pero ahí estaba y por supuesto todas las estructuras coincidían con otras imagenes ya conocidas.

Aunque el tutorial intenta ser minucioso yo aplicaría tambien otros procedimientos que en el tutorial no he incluido por razones de brevedad, por ejemplo, en el primer paso quizas habría que aplicar una mascara para no eliminar ciertas partes visibles de la nebulosa. Habría que aplicar mascaras de estrellas especificas en cada caso, por ejemplo para la deconvolución, etc.

Lo que si quisiera resaltar es la diferencia entre la resta de las escalas pequeñas que hay en otros tutoriales y la de este tutorial. En otros tutoriales de procesamiento por escala se hace una simple resta, pero esto puede suponer en el caso de que haya estrellas grandes que queden halos en la imagen de gran escala que despues se traducirán en halos en la imagen final. Mediante la formula de PixelMath del tutorial, que es la expresion utilizada comunmente para mezclar una mascara de luminancia con una de estrellas invertidas, evitamos ese problema, sobre todo si se hace bien el resalte de las pequeñas escalas para que enmascaren las estrellas gordas. Nos queda solo el fondo que es lo que nos interesa rescatar.

Por otra parte, en el tutorial se aplica 2 veces PixelMath pero también se podría haber procesado independientemente la imagen de gran escala y despues añadirla a la original como en otros tutoriales.

En cuanto a la traduccion, por motivos de trabajo imprevistos no pude hacerla ayer, a ver si hoy tengo un poco más de tiempo.

Un saludo, Silvercup.


Hi Maxi:

Tutorial main goal is just that. Recently I was able to reprocess an M81-M82 photo in which the author claimed that there was no sign of IFN and by this procedure I was able to show, very weak but there it was, and of course all the structures were consistent with other images already known.

Although the tutorial is intended to be thorough, I would also apply other procedures that in the tutorial I have not included for reasons of brevity, for example, perhaps the first step  it should be applied with a mask to avoid removing visible parts of the nebula. Masks should be applied expecificaly in each case, for example Star Mask for the deconvolution, etc.

What I want to highlight is the difference between the subtraction of the small scales that are in other tutorials and PixelMath operation in this tutorial. In other multi-scale processing tutorials  we do a simple subtraction, but this procedure, in the event that there were large stars, can produce halos in the large-scale image and then translated into star halos in the final image. Through the tutorial PixelMath formula, which is the expression commonly used to mix a luminance mask with a star mask inverted, we avoid this problem, especially if  we done the highlight of the small scales properly to mask the large stars. We obtain only the background that is what we want to rescue.

Moreover, in the tutorial  we applies PixelMath 2 times but large-scale image could also have been processed independently and then added to the original as in other tutorials.

As for translation, for work reasons I could't make it yesterday. I'll try today if I have a little more time.

Regards, Silvercup.