PixInsight Forum (historical)

PixInsight => Tutorials and Processing Examples => Topic started by: C. Sonnenstein on 2008 July 27 11:11:15

Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: C. Sonnenstein on 2008 July 27 11:11:15
[English readers below]

Hola a todos:

Me complace anunciaros un nuevo ejemplo de procesamiento llevado a cabo enteramente en PixInsight Core 1.2 con una imagen DSLR de M45 que muy amablemente ha cedido Ignacio Rico:
http://datastore.pleiades-astrophoto.com/csonnenstein/m45/tutorial_m45.htm

He intentado profundizar un poco en el manejo de algunos procesos, de manera que este documento no pretende ser solo un simple ejemplo de procesado. Por otro lado, he intentado también mostrar cómo procesar en PixInsight una imagen de cielo profundo que puede estar al alcance de todos, ya que la puede tomar cualquier aficionado sin necesidad de grandes medios.

Espero que os guste.

___________________________________________________________________________________

To english PixInsight Forum readers:

This PixInsight Core processing example will be translated in a few days, so please stay tuned. Thank you
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: OriolLehmkuhl on 2008 July 27 11:51:52
Buen tutorial Carlos  :)
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: Juan Conejero on 2008 July 27 17:11:21
Excelente trabajo Carlos. Enhorabuena ;)
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: Ignacio.R. on 2008 July 28 05:40:13
Pues ayer pille a unos amigos traduciendo un tutorial muy parecido a este. Que curioso  :lol:  :lol:  :lol:
Buen trabajo Carlos.  :wink:

Saludos
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: bosch on 2008 July 28 08:04:40
Gracias por compartir tus truquitos Carlos.
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: C. Sonnenstein on 2008 July 30 05:50:56
Gracias chicos, sin vuestro apoyo este trabajo no hubiese sido posible.
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: C. Sonnenstein on 2008 August 24 10:50:33
Appreciated forum readers:

Here is the English version of the document:
http://datastore.pleiades-astrophoto.com/csonnenstein/m45/en_tutorial_m45.htm

Many thanks to Oriol Lehmkuhl & Ivette Rodríguez for the collaboration of the translation.

We hope you like it.
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: Pep on 2008 August 29 18:08:03
Para los que estamos aprendiendo como es mi caso, con tutoriales como este se convierten en biblia. ¡Cuantas cosas que no hacía!

Felicidades y ánimos para un proximo.

P.D. Supongo que para imágenes CCD mono se puede utilizar estas mismas técnicas.

Saludos,
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: C. Sonnenstein on 2008 August 30 06:34:59
Hola Pep:

Por supuesto que se pueden utilizar las mismas técnicas descritas en este tutorial con imágenes monocromáticas, salvo la saturación de color y SCNR que obviamente solo son procesos que se aplican a imágenes en color.

Me alegro de que este ejemplo de procesamiento completo sobre una imagen DSLR de cielo profundo te sea útil. Aunque somos totalmente conscientes de que la documentación de la plataforma principal aún está pendiente de completarse, nosotros creemos que estos ejemplos y tutoriales también son muy útiles para comprender cómo y en qué situaciones se deben usar cada una de las herramientas que incluye PixInsight.

Por supuesto también estamos trabajando en desarrollar nuevas técnicas para procesar nuestras imágenes, y las herramientas necesarias para mejorar las capacidades y rendimiento del programa. Así que estad atentos porque muy pronto habrán novedades.

Un saludo.
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: Pep on 2008 August 31 00:02:54
Hola Carlos,
Como autodidacta que soy (me imagino  que como muchos de nosotros), para mi es mucho más comprensible un pequeño tutorial que un tocho de párrafo, ya que muchos de los términos que se utilizan me suenan a chino.

En los tutoriales-ejemplo, por lo menos vemos gráficamente la utilidad de las diferentes herramientas utilizadas, después que cada uno las aplique a sus imágenes como mejor crea.

Por mi parte, yo estoy intentando buscar y aprender que tipo de herramienta y en que caso se tiene que utilizar. Te pondré un caso: acabo de terminar un proyecto sobre alpha cisne, en Ha. Las tomas son de 40m, con la desgracia que la estrella alpha a caído por temas de estrella guía en uno de los laterales del chip, por lo tanto no veas la de donuts de reflexión que han aparecido. A lo mejor no se puede hacer nada, pero al igual existe alguna herramienta o método para poder quitar o al menos minimizar estos artefactos. El PixIn milagros no hace(creo) pero maravillas, creo que es un software indispensable para la astro-fotografía.

Si se te ocurre alguna idea me encantaría ponerla en práctica. :shock:

Saludos,
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: Nocturnal on 2008 October 05 12:03:24
Hello,

the English version gives a 404. I know I looked at it before, perhaps it was moved? I now have my own Pleiades to process so I thought I'd try to follow along with the tutorial :)
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: C. Sonnenstein on 2008 October 05 13:30:22
Sorry Sander, the server is actually not available. It will be in a few hours.
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: Juan Conejero on 2008 October 05 14:42:19
Hi Sander and Carlos

We are undertaking important changes in our file servers as a preparation to a complete renewal of our websites. As you have noticed, the server where this tutorial was stored is no longer available.

I have uploaded a temporary copy of Carlos' M45 tutorial:

English:
http://pixinsight.com/tmp/m45/en_tutorial_m45.htm

Spanish:
http://pixinsight.com/tmp/m45/tutorial_m45.htm

Sorry for the inconveniences.
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: Nocturnal on 2008 October 05 14:43:41
Thanks Juan and Carlos
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: Nocturnal on 2008 October 05 14:50:39
Looks like the document has absolute paths to the images rather than relative ones. They still point to the old location. It's easy enough to change the URL in my browser so I can see the images OK.
Title: Question about DBE and pseudo flat subtraction
Post by: lucchett on 2008 December 25 14:08:57
Hi Carlos,
I have a question:
as you are dealing with linear data in this tutorial (DSLR, right?), why do you subtract your background instead of dividing?

Is this related to the Pixinsight implementation of DBE or do you have any particular reason?


Thanks,
Andrea
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: Nocturnal on 2008 December 25 14:11:39
Hi,

doing DBE is not the same as flat fielding and IMO it does not replace it. You can apply a perfect flat field and still have gradients left over which DBE can handle. On the other hand if you did not apply a flat field then DBE can't fix the illumination differences.
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: Juan Conejero on 2008 December 25 15:12:24
Hi Andrea and Sander,

Quote
why do you subtract your background instead of dividing?


Because light pollution gradients are additive effects: they accumulate during the whole exposure time. Vignetting, on the other hand, is a multiplicative effect: it is a constant function that modifies the illumination distribution, independently on exposure time. For this reason, to correct for vignetting we multiply the image by the inverse of a special control frame that mimics the distribution of illumination on the focal plane.

Additive effects are in general impossible to predict, so the only way of removing them efficiently is to build and subtract a model of the illumination irregularities in the image. Fortunately, in deep-sky images we have a perfectly constant reference: the sky background. Since the sky background is constant (read flat), we can place samples on background areas of the image to build an accurate background model, which reproduces the existing illumination irregularities. DBE and ABE are two sophisticated image processing tools to build background models in PixInsight.

Note that background modeling and correction of multiplicative or additive effects have nothing to do with linearity of the data.

Quote
doing DBE is not the same as flat fielding and IMO it does not replace it


Actually not the same, but only for practical/methodological reasons. In theory, a synthetic background model could be as good as a natural flat frame. In practice, however, a natural flat frame is always preferable for two main reasons:

- When building a synthetic model, we can't isolate additive from multiplicative effects when both are present, as usually happens.

- Making an accurate flat frame is in general very easy, while building an accurate synthetic model is a delicate task, and sometimes it's almost impossible. For example, when there are very few background areas, we can make just an approximation based on marginal data (which is much better than nothing, of course :) ).
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: lucchett on 2008 December 25 16:54:06
Thanks Juan & Sander.

So, as I do take flat field frames (that I use to calibrate my images), if I want also to correct complex sky gradient using DBE I need to "subtract" .
I was mistaking!

Andrea
Title: Processing Example in PixInsight Core 1.2: M45 (The Pleiades Cluster)
Post by: Nocturnal on 2008 December 25 18:01:08
You got it Andrea. Different tools, different applications.