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  1. Galleries
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  3. Astrophotography
  4. » Trifid Nebula

 
Trifid Nebula...

Nebulose

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avatarsenior
sent on September 08, 2020 (17:45) | This comment has been automatically translated (show/hide original)

The first time I photograph the Trifid Nebula
is an emission nebula and a HII region located in Sagittarius.
It is called three dark lines of dust clouds that divide it into three parts
I love this shot because it is over-detailed thanks to the long focal point. It is usually framed in a much wider field, perhaps with the Lagoon
The Red of the Nebula is really evident, while the fine details of reflection in blue light are decidedly more muted

avatarsenior
sent on September 08, 2020 (18:36) | This comment has been automatically translated (show/hide original)

A qs focal and with qs definition by memory I do not remember to avela ever seen. Cmq is really gorgeous. There is very little to comment on. Wow. The only advice that I "allow" to give you is to try to remove 1 thread of saturation to the magenta because from the cel it seems to me 1 small evident in the outer part. Said qs tell you that it is from ep seems quite obvious and obvious. Very very nice.

avatarsenior
sent on September 08, 2020 (19:47) | This comment has been automatically translated (show/hide original)

Oh Stephen... warns before posting certain images! :-or :-D
Great, you've got a sensational amount of detail.
Confirm everything you say, few other objects know how to return such a clear color and avalanche details.... Cocoon or Iris comes to mind.
Compliments again.
Gp

avatarsenior
sent on September 08, 2020 (20:11) | This comment has been automatically translated (show/hide original)

more and more amazing and impressive! ;-)

avatarsenior
sent on September 08, 2020 (21:25) | This comment has been automatically translated (show/hide original)

Impressive, Congratulations.
Health, Save.

avatarjunior
sent on September 08, 2020 (21:27) | This comment has been automatically translated (show/hide original)

One of the most spectacular trifida images I've ever seen, so many compliments.

avatarsupporter
sent on September 08, 2020 (22:15) | This comment has been automatically translated (show/hide original)

Spectacular, as the whole series : nothing can be added but the most sincere compliments and, for sure, unequivocally deserved.

avatarsenior
sent on September 09, 2020 (7:54) | This comment has been automatically translated (show/hide original)

Thank you guys
Thank you for reporting on the magenta, I check as soon as I have a monitor properly. However, keep in mind that there's not only red in that part of the nebula, there's also blue so there's a little bit

avatarsenior
sent on September 09, 2020 (14:02) | This comment has been translated

Congratulations!

avatarsenior
sent on September 09, 2020 (15:05) | This comment has been automatically translated (show/hide original)

Great vision! Congratulations on the great work done and for the excellent explanation provided!
A :-o greeting

avatarsenior
sent on September 09, 2020 (15:50) | This comment has been automatically translated (show/hide original)

Just gorgeous.
great work and vision that you have proposed.
Hello Alexander

avatarsupporter
sent on September 09, 2020 (16:14) | This comment has been automatically translated (show/hide original)

Bravo Stefano, always great :-D

avatarsenior
sent on September 09, 2020 (19:30) | This comment has been automatically translated (show/hide original)

Thank you

P.S. I saw on another monitor actually the magenta is quite on.
I want to reverify the measures of abundance of blue Hbeta and Halpha to understand if my fusion algorithm has sung or makes sense ;-)

avatarsupporter
sent on September 09, 2020 (20:09)

Excellent! Beautiful picture.
Hello: Delphinus

avatarsenior
sent on September 09, 2020 (21:18) | This comment has been automatically translated (show/hide original)

Stefano let's be clear: let's talk about wool goat x the magenta :-D

avatarsupporter
sent on September 09, 2020 (22:56) | This comment has been automatically translated (show/hide original)

Spectacular!!!!! It looks like a rose blooming, an explosion of light. Congratulations. Say hello. Mama

avatarsenior
sent on September 10, 2020 (6:56) | This comment has been automatically translated (show/hide original)

we talk about goat wool

Cert, but now you have given me the "scientific" curiosity, since the color I did not by eye but in formula ;-)
Thodi I gladly investigate.
Curiosities are the basis of science

avatarsenior
sent on September 10, 2020 (7:09) | This comment has been automatically translated (show/hide original)

Stephen if you explain to me the concept of color to formula you would be grateful. :-o

avatarsenior
sent on September 10, 2020 (8:40) | This comment has been automatically translated (show/hide original)

Stephen if you explain to me the concept of color to formula you would be grateful. Eeeek!!!

Ri-quoto!

avatarsenior
sent on September 10, 2020 (13:13)


This comment is too long to be automatically translated, so it will be shown in its original language (Italian)  

Click here to translate the comment in English [en]


Immagino che sarà capitato anche a voi mille volte di mettere assieme riprese nei tre canali R, G e B poi iniziare a smanettare con regolazioni etc per trovare le colorazioni corrette dell'immagine.

Io uso pixinsight che ha un ottimo tool per bilanciare i colori che si basa sul fondo cielo e una stima della media delle stelle che si trovano nell'immagine. Nonostante questo non sempre si ottengono buoni risultati.

Un po di anni fa mi son stufato di andare a naso... una volta c'era inquinamento luminoso che modificava i "neri", una volta la nuvoletta di passaggio, un'altra riprendi una nebulosa che riempie il campo (come in questo caso) quindi non hai riferimenti da prendere per definire i neri... etc etc...

...per non parlare poi delle riprese in banda stretta da fondere con quelle a colori. Sono uno strazio

Stufo di perderci tempo tutte le volte, ho deciso di perdercene tanto ma una volta sola.. per tutte.

Ho fotografato oggetti di riferimento noti, stelle G2V, classi spettrali note, oggetti terrestri con colori facilmente definibili etc... tutto attraverso le ottiche che uso, la camera CCD e i suoi filtri

Normalmente si compone una immagine R G B partendo dalle immagini coi singoli filtri e assegnando dei pesi (che so 1 al blu, 0,8 al rosso, 0,6 al verde). La calibrazione la si fa su immagini di riferimento, vedi appunto le stelle classe G2V

Ho notato subito che questo metodo era insufficiente ad ottenere una buona rappresentazione dei colori. è una combinazione lineare semplice che funzionerebbe se le risposte in frequenza dei filtri fossero perfette.
Ma non è mai così. I filtri tipicamente lasciano passare anche lunghezze d'onda non desiderate, magari un blu fa passare anche dell'infrarosso

Son passato quindi ad una rappresentazione a matrice 3x3 dove ad esempio il canale rosso è combinazione lineare delle immagini prese con i filtri R G B, il verde pure e il blu idem.
Ovviamente il canale rosso avrà un peso molto alto sulla ripresa rossa, e debole sugli altri due filtri, e così anche per i canali verde e blu (nel verde domina il verde, nel blu il blu)
I coefficientidei vari canali possono esser anche negativi, che so ad esempio (non prendetelo come buono, solo come concetto)
Canale Rosso = 0.9 R + 0.15 G- 0.07 B
Canale Verde = 0,06 R + 0.8 G + 0.02 B
Canale Blu = -0.13 R + 0.21 G- 1.25 B


I coefficienti li ho tarati con tante prove fatte riprendendo soggetti noti

Poi non è proprio del tutto così semplice perché ci sono anche delle non linearità per gestire i risultati che verrebbero negativi, le saturazioni etc


A seconda del fatto che stia riprendendo nebulose o galassie e ci sia o meno banda stretta ho delle matrici che utilizzo (e aggiorno se vedo che è il caso)


A fine di questo processo faccio stime della luminosità di fondo cielo (riprendendo una zona di cielo limitrofa se serve dove ci siano solo stelle e cielo nero) e sottraggo tramite i tool di pixinsight sempre.
oppure uso le stime di pixinsight





Lo so, mi rendo conto, il principio è facile da capire, da mettere in pratica un po' meno. ci ho perso tanto tempo, ma di solito da quando lo uso ottengo risultati buoni e sensati.
Chiaro che rappresenta una base di partenza, poi ci si lavora sopra, però partire da qualcosa di buono serve sempre

Io credo che assomigli abbastanza a quel che vien fatto dalle macchine fotografiche e i programmi come Camera RAW che hanno i profili interni di queste macchine








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