Basic PixInsight processing example of a galaxy image

[Nocturnal]

The Google translation was funny so I thought I'd post it:

Hello everyone:

Firstly apologies for not following in English.
Vicent:
I am glad that you finally loosening garments.
Tomorrow will try to implement your "recipe" with one of my latest images.
I am curious to see what I get for the coefficients 400d modified using the procedure you described.
I suppose that may be applied to an image stack with DSS without corrections in RGB channels.

Anyway, if the algorithm works it shouldn't matter if DSS corrects the RGB channels or not.

-----

De todos modos, si el algoritmo no debe importar si el DSS corrige los canales RGB o no.

[vicent_peris]

Me alegro de que por fin vayas soltando prendas.

Bueno, el método de arriba ha sido totalmente improvisado en un ratito esta tarde. :-P

Supongo que se podrá aplicar a una imagen apilada con DSS sin correcciones en los canales RGB.

Por supuesto. No le digas al DSS que haga nada, hazlo tú mismo, que siempre tendrás mejor control sobre las cosas.

Suerte, ya nos contarás!
Vicent.

[georg.viehoever]

Vincent,

I tried it on my Lulin picture picture that I stacked with DSS. It works perfectly well! The remaining touch up was entirely for aesthetic reasons.

Thanks for this nice procedure!

Georg

PS: And if possible, please answer in English even to spanish posts. I have no way of reading spanish, while most people on the internet at least can *read* English (even if writing English is more difficult for them). The google translations are sometimes quite funny   and misleading    .

[vicent_peris]

For George, translation:

Me alegro de que por fin vayas soltando prendas.

Bueno, el método de arriba ha sido totalmente improvisado en un ratito esta tarde. :-P

Well, the method has been completely improvised this afternoon. :-P

Supongo que se podrá aplicar a una imagen apilada con DSS sin correcciones en los canales RGB.

Por supuesto. No le digas al DSS que haga nada, hazlo tú mismo, que siempre tendrás mejor control sobre las cosas.

Of course. Don't tell DSS doing anything, juts do it by hand, you will have always more control over your work.


Regards,
Vicent.

[Juan Conejero]

Simplified PixelMath expressions for color calibration:

Code: [Select]

($T[0] - Med( bg[0] ))*Avg( color[1] )/Avg( color[0] ) + Med( bg[0] )
$T[1]
($T[2] - Med( bg[2] ))*Avg( color[1] )/Avg( color[2] ) + Med( bg[2] )

Of course, this expression must be applied with rescaling disabled. It preserves the initial mean background of the target image, which is being sampled with the bg image.

For these expressions to work properly (or at least, to work as they are intended):

1. The main contribution to the histogram's shape must come from enough free sky background pixels.

2. The image must be accurately calibrated (flat fielded).

3. The mean background should be neutral.

Recall that to neutralize the background, the following expression can be applied (provided that conditions 1 and 2 above hold):

Code: [Select]

$T - Med( $T )

with rescaling enabled. Or, if rescaling isn't acceptable:

Code: [Select]

$T - Med( $T ) + k0

where k0  must be defined as a suitable pedestal to avoid zero clipping (e.g., k=0.05 or something similar).

[ManoloL]

Hola Juan:

De nuevo pido disculpas por no ser capaz de expresarme adecuadamente en inglés, aunque no tengo ningún inconveniente en que la respuesta sea en ese idioma.
El método expuesto es adecuado para dejar un cielo neutro.
Pero si como ocurre en mi caso el cielo tiene una contaminación lumínica apreciable  y por lo tanto es rojizo, al aplicar las formulas el cielo dejará de ser rojo, pero las estrellas tenderán a tomar colores azulados, incluidas las que no lo son.
Al menos esa es mi experiencia, lo cual no quiere decir que el hecho citado se haya producido por otras causas que no haya sido capaz de controlar.
Creo que como paso previo a esa neutralización del cielo es necesario la aplicación de los coeficientes obtenidos por los métodos anteriormente citados u otros.

Saludos.

[Simon Hicks]

Hi all,

I've been reading this with great interest. I tried some of these techniques last night and it really did seem to work. I needed all the procedures and equations printed out in front of me, and then typing them into PixelMath was quite laborious.....but worth it in the end.

Would it be possible for someone with the right skills to turn this procedure into a PI Module or Script?

Maybe even a single icon or button for "Neutralise Background" would be useful.....I know its only one line of code to enter into PixelMath....but that means opening PixelMath, deleting the three lines of complex code already in it, then entering the one line of code, then checking all the rescale boxes, etc, then executing it. Of course I am exagerating the effort, but hopefully you get my point.

Its so fundamental to the processing of the vast majority of astro images that it would be a really cool addition to PI.

Just a thought.

Cheers
              Simon

[Juan Conejero]

Hi Simon,

I have good news indeed. Both tools will be included in PixInsight 1.5. They are the ColorCalibration (CC) and BackgroundNeutralization (BN) tools. CC is finished at a 90% now; BN is quite simple, so it will be ready tomorrow in an hour or so

Version 1.5 was scheduled for March, but the addition of new tools (a total of five) and the complexity of the first 64-bit version for Mac OS X have delayed it. It should be released in a couple weeks or so.

[Simon Hicks]

Yeehar! Superb news Juan...you're a STAR!  Can't wait for version 1.5.

[Nocturnal]

Hi Simon,

in the meantime you should be able to use copy/paste to get the equations from your browser into pixelmath, right? Then drag an instance to the workspace and save it with your other processing icons. I'm pretty sure that opening a psm file wipes your current processing icon set which is a bit painful but maybe you can make it work until 1.5 comes out.

[Simon Hicks]

Hi Sander,

save it with your other processing icons

.....what icons?  :lol:   I sort of suspected you could save your own icons, but I had no idea how...embarrasing huh!

So following your suggestion I have been investigating saving and loading icon files and psm files. Wow, life is going to be much simpler now. This is a really cool feature....but I guess you already know that.  :lol:

Every day, something new to learn. Is there a tutorial somewhere on saving icons and psm files?

Cheers
              Simon

[Nocturnal]

Hi Simon,

I'm glad I was able to help. I don't think there's a tutorial on this subject somewhere but once you get the basics, like you do now, I don't think there's a need to. What specifically are you looking for? If you're not comfortable with processing icons in general I can recommend that you re-visit Juan's excellent videos which deal with them on occasion.

[Simon Hicks]

Hi Sander,

I'll keep playing...I think I am 80% there, fingers crossed.

Cheers
             Simon