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Sergio
D√≠az‑Ruiz
Universe photography
@blog‚§ī
Fenómenos triples de los satélites galileanos 2025-2049
J√ļpiter

2023-05-28 ― En el post sobre fen√≥menos de los sat√©lites galileanos mencion√© el trabajo realizado en 2002 por Jean Meeus, 'Jupiter: Triple Satellite Phenomena', en el que presenta aquellos fen√≥menos m√ļltiples, sombras o tr√°nsitos, que **involucran simult√°neamente a tres de los sat√©lites**, en el periodo 1981-2040. Dada la resonancia orbital entre √ćo, Europa y Ganimedes, no es posible que los tres se presenten en conjunci√≥n simult√°neamente, por ello todos los fen√≥menos "triples" involucran siempre a Calisto, tal como explica Meeus. ¬∑¬∑¬∑⇝

Astronomy Photographer of the Year 2023
Imagen clasificada en el concurso Astronomy Photographer of the Year 2023

2023-06-27 ― Estoy encantado de tener una imagen clasificada en la 15¬™ edici√≥n del concurso Astronomy Photographer of the Year. Es el tercer a√Īo consecutivo y no me lo creo todav√≠a.

Esta vez me he salido de mi zona de confort y he tratado de representar los datos del sobrevuelo de Plut√≥n de New Horizons con estilo de grabado antiguo, inspirado en la cautivadora 'Carte de La Lune' (Cassini, 1679). La imagen ha sido seleccionada dentro de la categor√≠a especial Annie Maunder Prize for Image Innovation, introducida por primera vez en la edici√≥n del a√Īo 2020. En esta categor√≠a el objetivo es conseguir una imagen innovadora aprovechando datos p√ļblicamente accesibles capturados por telescopios profesionales, pudiendo combinar distintas fuentes (NASA, ESA, ESO, etc.). ¬∑¬∑¬∑⇝

Configuraci√≥n de la Mancha Roja de J√ļpiter en Stellarium
Mancha Roja de J√ļpiter

2023-05-29 ― La posici√≥n de la Mancha Roja (GRS, Great Red Spot) en Stellarium puede diferir notablemente respecto de lo observado o de otras fuentes (Sky Safari, Sky&Telescope, etc). A diferencia de otras caracter√≠sticas de este software, los valores configurados por defecto para la predicci√≥n de la posici√≥n de la GRS pueden no ser adecuados, especialmente si lo hemos actualizando sin reemplazar el fichero de configuraci√≥n, como es lo habitual. ¬∑¬∑¬∑⇝

Tránsitos y sombras de los satélites galileanos 2023-2028
J√ļpiter

2023-05-28 ― Los fen√≥menos de los sat√©lites galileanos de J√ļpiter, es decir, Io, Europa, Ganimedes y Calisto, son siempre objeto de inter√©s para la observaci√≥n visual y la astrofotograf√≠a planetaria. Aqu√≠ nos centraremos en los tr√°nsitos de estas lunas a trav√©s del disco aparente del planeta y de la proyecci√≥n de sus sombras sobre el mismo, y en particular en los que ser√°n observables desde Sevilla, haciendo √©nfasis en los casos en que concurren varios de estos fen√≥menos. Si bien el Institut de m√©canique c√©leste et de calcul des √©ph√©m√©rides (IMCCE) proporciona efem√©rides sobre estos eventos, no agrupa los fen√≥menos como haremos aqu√≠, lo que nos permitir√° explorar aquellos m√°s complejos para planificar nuestras observaciones. Por otra parte, el trabajo del c√©lebre Jean Meeus 'Jupiter: Triple Satellite Phenomena' se centra √ļnicamente en los fen√≥menos m√°s complejos, en lo que se ven involucradas tres lunas simult√°neamente. ¬∑¬∑¬∑⇝

Fenómenos de Titán durante el alineamiento de los anillos de Saturno (2024-2026)
Tit√°n

2023-05-01 ― A finales de marzo de 2025 los anillos de Saturno se pondr√°n de canto desde nuestra perspectiva. El plano orbital de sus sat√©lites es pr√°cticamente el mismo que el de los anillos, por lo que esta orientaci√≥n propicia la ocurrencia de tr√°nsitos, sombras, eclipses y ocultaciones de los sat√©lites por parte del disco de Saturno. En particular, por su tama√Īo y brillo, los fen√≥menos de Tit√°n deben ser los m√°s f√°cilmente detectables con medios amateur (aunque no ser√° sencillo, considerando que Tit√°n presenta un di√°metro aparente en torno a 0,7"). ¬∑¬∑¬∑⇝

Junocam image processing
Junocam image processing

2022-04-23 ― After playing around with some Junocam preprocessed images ("map projected", as they appear on the image processing website), I wanted to give a try starting from the raw images instead.

Junocam raw images are 8-bit monochrome PNGs composed of stripes or "framelets" vertically stacked in groups of three, corresponding to the blue, green, and red filters. To assemble the puzzle, what the knowledgeable people do is to three-dimensionally project the framelets to a spheroid representing Jupiter and then take a snapshot to this map-projected spheroid. In fact, they even correct the framelets for optical distortion induced by the camera lens. They use tools like ISIS and SPICE kernels and things out of my reach at least by now; see "My frustrating walkthough to processing Junocam raw images" by cosmas-heiss (github) and "Processing JunoCam Images" by Kevin M. Gill (github). ¬∑¬∑¬∑⇝

Background Optimization Tool Examples
Background Optimization Tool Examples

2022-05-22 ― Here I would like to show some examples of background subtraction done with the background optimizer tool presented here. The background extraction is usually more challenging on widefield and/or star-crowded images, so I tried to pick up some more or less illustrative examples of these among my own data.

All images used were in linear state when I applied the tool to them. Here they are shown after delinearization, just for visualization purposes. In this case, the delinearization is just a histogram stretch based on the automatic SFT (Screen Transfer Function) of PixInsight. ¬∑¬∑¬∑⇝

Background modeling via spline gradient descent optimization
Background modeling via spline gradient descent optimization

2022-02-06 ― Some of the light we capture does not come from the object we are photographing. Moonglow, airglow, and, unfortunately, light pollution, get all the way to our pixels. These 'background' light sources are unwanted and they get mixed unavoidably with our object signal.

Essentially we are assuming that our image can be decomposed as the sum (or maybe the multiplication) of an object term and a sky background term. If we compute an estimation of the second, we can recover to some extent the object term by subtracting the background estimation from the original image. ¬∑¬∑¬∑⇝

Multiband mapping for astrophotography based on PCA
Multiband mapping for astrophotography based on PCA

2021-12-23 ― Color mapping is always challenging in astrophotography, especially when we have observations of the same astronomical object in multiple spectral bands. Here, I propose a possible method to approach this problem based on a well-known machine learning algorithm borrowed from classic statistics, the Principal Component Analysis (PCA), to compress information from the multiband input data into RGB channels while minimizing information loss. This technique could also be applied to narrowband-only "SHO" data to find an encoding that deals with the typical H-alpha overwhelming signal. ¬∑¬∑¬∑⇝

Alegaciones al "Proyecto de decreto por el que se aprueba el reglamento de protección frente a la contaminación lumínica en Andalucía"
Alegaciones al

2021-12-23 ― Lo que sigue son las alegaciones que he presentado a t√≠tulo particular al proyecto de decreto de la comunidad andaluza que pretende reglamentar la protecci√≥n frente a la contaminaci√≥n lum√≠nica, por desgracia con muy poco tino, al igual que est√° ocurriendo con la revisi√≥n del reglamento de eficiencia energ√©tica a nivel nacional. ¬∑¬∑¬∑⇝

Shorlisted images on the Astronomy Photographer of the Year 2021 competition!
Shorlisted images on the Astronomy Photographer of the Year 2021 competition!

2021-06-21 ― Update 16th Sep 2021: my image Another Cloudy Day on Jupiter: A Surface Map Based on 8 Filters Data was selected as the winner of the Annie Maunder category jointly with Leonardo DiMaggio's "Celestial Fracture".

I am more than delighted to announce that not one, but two of the images I submitted to the Astronomy Photographer of the Year 2021 competition have been shortlisted under the Annie Maunder Prize for Image Innovation category, first introduced in the 2020 edition. In this category the objective is to achieve an innovative image taking advantage of publicly accessible data captured by professional telescopes, being able to combine different sources (NASA, ESA, ESO, etc.). ¬∑¬∑¬∑⇝

Im√°genes clasificadas en el concurso Astronomy Photographer of the Year 2021
Im√°genes clasificadas en el concurso Astronomy Photographer of the Year 2021

2021-06-21 ― Actualizaci√≥n 16 Sep 2021: Another Cloudy Day on Jupiter: A Surface Map Based on 8 Filters Data ha sido seleccionada como ganadora del Premio Especial Annie Maunder junto con la imagen de Leonardo DiMaggio "Celestial Fracture".

Estoy m√°s que encantado de anunciar que no una, sino dos de las im√°genes que present√© al concurso Astronomy Photographer of the Year 2021 han sido preseleccionadas bajo la categor√≠a especial Annie Maunder Prize for Image Innovation, introducida por primera vez en la edici√≥n del a√Īo 2020. En esta categor√≠a el objetivo es conseguir una imagen innovadora aprovechando datos p√ļblicamente accesibles capturados por telescopios profesionales, pudiendo combinar distintas fuentes (NASA, ESA, ESO, etc.). ¬∑¬∑¬∑⇝

XISF Format Decoder/Encoder Module for Python
XISF Format Decoder/Encoder Module for Python

2021-06-13 ― PixInsight uses natively its own, but openly documented, file format to store images (and other objects), called XISF, and pronounced more or less like... a sneeze.

When experimenting with astronomical images processed with PixInsight on scikit-learn or Keras python libraries, I found myself converting them to TIFF or the old FITS or format and then using scikit-image or astropy to load them, because there is no native way in python to load XISF files. ¬∑¬∑¬∑⇝

Reproducibility in PixInsight
Reproducibility in PixInsight

2021-06-12 ― When working on image with PixInsight (PI), I usually split the processing in two PI projects: one for all the preprocessing steps, including calibration, registration and integration, with the master files as output, and other project for all the postprocessing, linear and nonlinear stages, with the final image as output.

The preprocessing project is usually straightforward in terms of the workflow, being a sequence of steps (despite all the iterations until I get everything mostly right). ¬∑¬∑¬∑⇝

What is Astrophotography?
What is Astrophotography?

2021-06-10 ― Before starting to read the book 'Photographing the Invisible' by Vicent Peris, as an exercise I began to describe in my own words what astrophotography is for me, firstly because it was something that I had never stopped to do, and secondly, to establish a posteriori what influence the book had on my vision. What follows is nothing more than the result of that exercise. ¬∑¬∑¬∑⇝

¬ŅQu√© es la astrofotograf√≠a?
¬ŅQu√© es la astrofotograf√≠a?

2021-06-10 ― Antes de empezar con la lectura del libro 'Fotografiar lo Invisible' de Vicent Peris, me puse como ejercicio describir con mis propias palabras qu√© es para m√≠ la astrofotograf√≠a, primero porque era algo que nunca me hab√≠a parado a hacer, y segundo, para valorar a posteriori qu√© influencia hab√≠a tenido el libro. Lo que sigue no es m√°s que el resultado de dicho ejercicio. ¬∑¬∑¬∑⇝

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