Another Ha Combine question

[Jack Harvey]

One of the problems with combining an Ha frame with say a Red is the FWHMs are different and you often get that bullseye appearance with the smaller Ha inside the Red star.  Is there a way to quickly calculate how much to deconvolve the red frame to get a better fit with the smaller FWHM of the Ha?  Thanks.






Uno de los problemas de combinar un marco con Ha decir Roja es la FWHMs son diferentes y que las que suele llegar con la aparición bullseye Ha menor en el interior de la estrella Roja. ¿Hay una manera de calcular rápidamente la cantidad a la deconvolve marco rojo para obtener un mejor ajuste con los más pequeños de la FWHM Ha? Gracias.

[LD]

HI again Jack,
Seems like we're both stuck on this (although I wish I had your excellent images to play around with :wink: .)I know I'm no expert here so I'll just quote Vicent:

For the star size problem, we can combine both images with a Maximum operator (this operator will choose the maximum of each pair of values of both images). So as a result, we will have an image with bigger stars. BUT a part of the noise from the red image will be transferred to the information of the H-alpha nebula.

The easiest method I think now is simply multiplying the H-alpha image by a factor of >1. As the stars are very much dimmer in the H-alpha image, by multiplying this image you will end with a picture in wich the stars are of the desired size, but with the inmaculateH-alpha information from the nebula.

I hope this is what you had in mind.

Larry

[Jack Harvey]

I missed that section.  Thanks I will play with that some.

[Jack Harvey]

I tried that rick and did not get the Ha star sizes to increase ntoiceably, even when using 6x?  SO maybe there is a step I am missing???

[vicent_peris]

I tried that rick and did not get the Ha star sizes to increase ntoiceably, even when using 6x?  SO maybe there is a step I am missing???

Hi Jack,

I was talking about PixelMath, not Morphological Transform.  :wink:

Good luck,
V.

PS: On that message, I simply gave some ideas, as I'm not an expert in narrowband imaging.

[Juan Conejero]

Hi Larry and Jack,

I think what Vicent was referring to is something like this applied with PixelMath:

Code: [Select]

Max( halpha, 0.7*red )

where halpha and red are your Ha and red frames, respectively. The 0.7 multiplying factor is just an example; you have to find the appropriate value by trial-error.

The expression above should be applied to the halpha image, to form the new combined red channel image. You can easily try it out on a preview.

The idea behind this expression is replacing Ha pixels where red is stronger than Ha. This happens basically around stars, since these are larger on the red image. However, as Vicent pointed out, one problem is that by doing this some noise from the red frame is transferred to the Ha frame, which is not good at all. Hence the multiplying factor in the expression above.

Another way to avoid noise transference is using a star mask when applying the expression above. Such a mask would protect the background and relatively dim regions, where we want no red pixels at all. The mask should be active for the halpha image, which is the target of PixelMath in this case.

Vicent, please correct this if I'm wrong.

Hope this helps

[LD]

Another idea: perhaps you could simply eliminate the stars in the Ha image by subtracting them with another image of small scale made with A Trous Wavelets. You really don't need the star data from the Ha image in the first place, I would imagine. The only danger here would be eliminating small scale structures you want to keep.
Just another 2c
Larry

[vicent_peris]

hum hummmm....

I think there is a big problem in this topic... As Jack pointed out, usually the stars are bigger in the broadband images. If you have compare an H-alpha image to a red image, of course you will have more nebula data in the narrowband image... BUT those tiny stars are so wonderful in this image...  :wink:  

I think the perfect HaRGB image would be the one with all the H-alpha data (without any noise degradation), AND with the tiny stars from the narrowband image.

Could you guys upload some test data? Sincerely, I'm not be able to build a workflow on this topic only with my imagination... I have some ideas (basically making the broadband stars to go to the size of the narrowband ones, and rescaling them by a factor to adjust their brightness to the narrowband image). I think it would be very nice for this topic to have some sample images. Perhaps a small crop of a raw image in each filter.


Regards,
Vicent.

[Jack Harvey]

I have some nice master frames on NGC 2074 which I am happy to share.  I do not seem to be able to figure3 out how to send this stuff to the ftp.

[Jack Harvey]

Thanks to Juan who got me hooked up with the http://pteam.pixinsight.com/.  I have uploaded the master frames for NGC 2074.  The broadband frames are registered to the Ha frame.  Also I got two sets of Red data (R1 and R2) with the idea of using one set to combine with the Ha and the other to use for the RGB.  It is under the folder jack.harvey on the public http://pteam.pixinsight.com/.

So here we go Vincent, LD et al. -  now we can play with this data<G>

BTW please credit SSRO/PROMPT if you post this data anywhere  ie  "this image based on data acquired by SSRO/PROMPT 2007"

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Gracias a Juan quien me consiguió conectar con el http://pteam.pixinsight.com/. He subido el capitán marcos para NGC 2074. La banda ancha de imágenes que se registraron a la Ha marco. También me dieron dos conjuntos de datos Roja (R1 y R2) con la idea de utilizar un conjunto de combinar con la Ha y la otra de su uso en la RGB. Se encuentra bajo la carpeta en la vía pública jack.harvey http://pteam.pixinsight.com/.

Así que aquí vamos Vicente, LD et al. -- Ahora podemos jugar con estos datos <G>

BTW crédito por favor SSRO / PROMPT si después estos datos en cualquier lugar, es decir "esta imagen sobre la base de datos adquirida por SSRO / PROMPT 2007"

[vicent_peris]

Ok, thanks you very much, Jack!

I'm playing a bit with the data. For the moment, I have a Red image without H-alpha emission:




It can be very useful for making possible masks... I will continue working...



Regards,
Vicent.

[Jack Harvey]

Vincent  Glad you found the data.  BTW I did correct the link to the ftp in the post above so others can now access the data.  Thanks again Juan!

I will be watching for developments along this front (as will LD I am sure<G>)

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Vicente encantados de poder encontrar los datos. BTW yo lo hice corregir el enlace al ftp en el puesto más arriba para que otros usuarios puedan acceder ahora a los datos. Gracias de nuevo Juan!

Voy a cuidarme de los acontecimientos a lo largo de este frente () 2007 "

[vicent_peris]

Ok, I have it!  :wink:

I post here my results, and I will write ASAP the method. This method is easily scriptable, so I think we will have a narrowband imagen color combination.


This is the original combined RGB data:



And this is the h-alpha enhanced image:



For a better comparison with the original RGB image, I've adjusted the midtones of the last image to decrease the brightness of the nebula to fit it to the original RGB. You will see that the stars seem to disappear.  :wink:



You can control the H-alpha emission enhancement. This example is a bit extreme, I've multiplied the H-alpha signal by x12, but a lower factor like x5 works too very well too.


Hope you like it.
Vicent.

[Jack Harvey]

That is looking very good.  I assume you will have more on how to do this in the future.  Maybe in the far future a Ha LRGB or Ha RGB Combine function like the LRGB would be a possibility.  You could plug in the Ha, R,G, B frames and adjust how much Ha and how much multiplication to dial in<G>.

Thanks for all the work VIncent - and quick too!

[Jack Harvey]

I tried Vincent's method and used an HaR that I multiplied by 10 and then combined that result with a RGB.  Needed some Histogram black point adjustment, slight color saturation and curves.  Finally a touch of GreyCstoration for smoothing.  It is in my folder on the PixInsight file server since I do not know how to put an image on this forum.

The good news is I think Vincent has solved the star problem!


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Traté Vicente del método y utilizado un HaR que multiplicado por 10 y, a continuación, resultado que combinado con un RGB. Necesarios algunos ajustes de histograma punto negro, de saturación de color ligero y de curvas. Por último un toque de GreyCstoration de suavizado. Es en mi carpeta en el servidor de archivos desde PixInsight no sé cómo poner una imagen en este foro.

La buena noticia es que creo que Vicente ha resuelto el problema estrellas!