Starship Asterisk*

as a child when i was growing up, i remember seeing pictures in limited resolution. with modern day advances,its incredibly breathtaking to see these objects with such clarity ! were a fortunate generation to have this capability to witness the cosmos like never before. our forefathers could only dream of seeing images like these !

Fantastic image Rogelio

Sorry to chime in late.

For me, these mosaics are anything but easy, compared to one-frame shots. And time consuming too, of course.
I do apply the method Chris stated: stitch each channel data separately.
Gradients are a HUGE problem, and it's often very very difficult to solve (there you have one of the many challenges that makes these mosaics anything but easy, for me at least).

Leaving all that aside (I could talk/write about it for hours), this image contains data from another image I produced last year, of the Horsehead+M42 area, and that certainly added to a less than perfect homogeneous color balance across the entire field. This does not bother me, as I believe the image meets the qualifications for an "outreach image" without really inventing anything. It is in fact an unfinished work in some regards (I won't get into the details at this moment though).

Cheers,
Rogelio

[quote="Ann"]I should let Rogelio speak for himself here, but I believe that he hadn't planned to make this huge mosaic from the beginning. I think he started the Horsehead and Orion's Belt region, and then he stitched that together with a mosaic of the Orion Nebula and its surroundings. This part of his image is rather blue in color balance, and there is a lot of blue light to record here, too. But when Rogelio decided to image the rest of Orion, too, he may have decided to get a lot of Ha exposure to really capture Barnard's Loop and the Lambda Orionis region, and in that way different parts of his huge mosaic may very well have different color balances.[/quote]
It doesn't matter. The way you make mosaics is to piece together the individual filtered layers first. You don't make a bunch of separately processed color images and then put those together. So you are starting with a huge image that you apply your color balancing technique to, so there is no reason for different zones to show different color balances.

[quote]Like I said, I should really let Rogelio speak for himself. But I must say that hardly anoyone else makes the kind of mega-mosaics that Rogelio produces, and the reason why practically no one else makes these mosaics must be that they are very hard and time-consuming to produce.[/quote]
Not especially hard, but very, very time consuming, between collecting so much light and working with such massive images (assuming that he didn't scale them down before processing, which might be a reasonable thing to do, depending on the rendering intent).

I should let Rogelio speak for himself here, but I believe that he hadn't planned to make this huge mosaic from the beginning. I think he started the Horsehead and Orion's Belt region, and then he stitched that together with a mosaic of the Orion Nebula and its surroundings. This part of his image is rather blue in color balance, and there is a lot of blue light to record here, too. But when Rogelio decided to image the rest of Orion, too, he may have decided to get a lot of Ha exposure to really capture Barnard's Loop and the Lambda Orionis region, and in that way different parts of his huge mosaic may very well have different color balances.

Like I said, I should really let Rogelio speak for himself. But I must say that hardly anoyone else makes the kind of mega-mosaics that Rogelio produces, and the reason why practically no one else makes these mosaics must be that they are very hard and time-consuming to produce.

Ann

[quote="Ann"]Well, perhaps they do pose special challenges, if the individual images were taken at very different times and possibly with different filters and with different times of exposure.[/quote]
Normally, if you are composing a mosaic you aim for all the frames to be collected with the same filters and exposure times. However, using the same exposure times isn't critical. CCDs are highly linear, so you can scale the individual frames to get the same signal with each (but not the same S/N). So the only factor becomes position in the sky. But nobody putting together a serious image is going to be working so low that atmospheric extinction will produce a visible shift in intensity or color. Light pollution gradients can be a problem, but I assume this was shot from a fairly dark location, and fairly high in the sky.

So the process of managing color in the case of a large mosaic like this is identical to that of handling the color for any one of the frames that make up the whole thing.

[quote="Chris Peterson"][quote="Ann"]As for Rogelio's absolutely amazing Orion constellation image, it is a huge mosaic that has been stitched together from an incredible number of individual frames. This means that it is almost impossible to make the color balance and color saturation the same all over the picture.[/quote]
Ann, that is completely untrue. Mosaics pose no special challenges at all with respect to color management. Or to express it better, they pose exactly the same challenges that individual images do.[/quote]

Well, perhaps they do pose special challenges, if the individual images were taken at very different times and possibly with different filters and with different times of exposure.

Ann

[quote="Ann"]As for Rogelio's absolutely amazing Orion constellation image, it is a huge mosaic that has been stitched together from an incredible number of individual frames. This means that it is almost impossible to make the color balance and color saturation the same all over the picture.[/quote]
Ann, that is completely untrue. Mosaics pose no special challenges at all with respect to color management. Or to express it better, they pose exactly the same challenges that individual images do.

Leon, I, too, enjoy your posts.

As for Rogelio's absolutely amazing Orion constellation image, it is a huge mosaic that has been stitched together from an incredible number of individual frames. This means that it is almost impossible to make the color balance and color saturation the same all over the picture. As a consequence of this, Barnard's Loop and the Lambda Orionis Nebula look brighter here in red hydrogen alpha light than the Orion Nebula and the red background to the Horsehead nebula.

However, this not quite perfect balancing of the relative brightness of various nebulae in Orion brings out a remarkable fact about this entire constellation. It is a bit like a nearby version of the Soul Nebula!

[img2]http://www.atlasoftheuniverse.com/nebulae/ic1805.jpg[/img2]
This is the Soul Nebula on the left and the Heart Nebula on the right. Isn't the Soul Nebula remarkably similar to the entire Orion constellation in Rogelio's picture? Like the Soul Nebula, the constellation Orion has a big round red nebula "to the left" (at least it is to the left in this image). As is the case in the Soul Nebula, this big round red nebula "to the left" appears to be ionized by just one hot bright star. Like the Soul Nebula, Orion has a long rounded red arc or ridge which marks the lower edge of the nebula. Like the Soul Nebula, this red ridge seems to encircle a large starforming region with two concentrated regions of young blue stars inside. And like the constellation Orion, the Soul Nebula even appears to have a "Rigel" more or less at Rigel's position in relation to the large starforming region in Orion!

I've never seen the similarity between the constellation Orion and the Soul Nebula before. Thanks for wowing me not only with your amazing picture of Orion, but also with similarity of Orion to other star forming regions that your image brings out in a fantastic way.

Ann

[quote="biddie67"]Leon - your translator creates fascinating and tantalizing snippets of, at times, almost mystical thoughts - I enjoy reading them many times not only to "untranslate" to get to what your original thoughts were but to see what a translator does in its unthinking methods.[/quote]

Thanks Biddie for your concepts, you're too kind, not always seem to say in English as I have thought and even written in Spanish, retouch far gives me the knowledge, today was well done.

I always look up in the winter sky to find Orion. It's my favorite constellation, but I never imagined how beautiful it is. I tell you it left me speechless. This is definitely my favorite APOD picture. Rigelio you have out done yourself.

FS

Rogelio - wonderful, wonderful work !!!! Your pictures truly bring to us the AWE from the out there ....

Leon - your translator creates fascinating and tantalizing snippets of, at times, almost mystical thoughts - I enjoy reading them many times not only to "untranslate" to get to what your original thoughts were but to see what a translator does in its unthinking methods.

Rogelio mosaics are, increasingly, higher levels of difficulty. In another forum someone asked why not make another four pictures and include the witch head nebula? Seemed excessive, but knowing the work of Rogelio, his commitment and degree of perfection, no doubt eventually will.
New Congratulations to Rogelio, I think it takes 14 APOD.
Greetings
César

Love these kind of pictures in APOD 8-) 8-) :) :)

[quote="Ann"]

Wow, Rogelio has outdone himself!!! Fantastic!!![/quote]
[img3="[size=200][color=#0000FF]Orion in true blue colors[/color][/size]"]http://2.bp.blogspot.com/__ccFdtNtgaE/TCCx5bWu8LI/AAAAAAAAAzc/OcjKzL_i0eU/s1600/The+Cookie+Monster+Cometh.JPG[/img3]

Orion is the center of the sky, especially in the southern hemisphere that we have in the days of summer, when viewing the sky with more regularity.

In the south we see invested, at the zenith at the beginning of summer, with Sirio at Right and Pleyades to left.

[img]http://www.mateando.com/images/users/8112/orion_spinelli_c1.jpg[/img]

Orion is attributed to the accruing of the human race, the extraordinary myth or reality accompanying molecular nebula can not rule out the approach to the origin.

The Arabic name of the majority of stars in the constellation stands shoulder to a town whose geographic conditions required him to live in intimacy with the stars.

The proliferation generation of stars that continue to contribute from the heated regions of the nebula may be presumed that his prominence will not wane in the future.

JUST PLAIN AWESOME!
M42 is one of my favorites!

Wow, Rogelio has outdone himself!!! Fantastic!!!

Ann

[url=http://apod.nasa.gov/apod/ap101023.html][img]http://apod.nasa.gov/apod/calendar/S_101023.jpg[/img] [size=150]Orion: Head to Toe[/size][/url]

[b] Explanation: [/b] Cradled in cosmic dust and glowing hydrogen, [url=http://archive.ncsa.uiuc.edu/Cyberia/Bima/StarForm.html]stellar nurseries[/url] in Orion the [url=http://www.clarkfoundation.org/astro-utah/vondel/slimone.html]Hunter[/url] [url=http://www.seds.org/messier/more/oricloud.html]lie at the edge[/url] of a giant molecular cloud some 1,500 light-years away. Spanning nearly 25 degrees, this breath-taking vista stretches across the well-known constellation from head to toe ([url=http://homepage.mac.com/kvmagruder/bcp/literature/frost.htm]left to right[/url]). The [url=http://en.wikipedia.org/wiki/Orion_Nebula]Great Orion Nebula[/url], the closest large star forming region, is right of center. To its left are the [url=http://apod.nasa.gov/apod/ap100513.html]Horsehead Nebula[/url], [url=http://apod.nasa.gov/apod/ap100302.html]M78[/url], and [url=http://apod.nasa.gov/apod/ap061229.html]Orion's belt[/url] stars. Sliding your cursor over the picture will also find red giant [url=http://apod.nasa.gov/apod/ap100106.html]Betelgeuse[/url] at the hunter's shoulder, bright blue [url=http://stars.astro.illinois.edu/sow/rigel.html]Rigel[/url] at his foot, and the glowing Lambda Orionis ([url=http://www.gb.nrao.edu/~rmaddale/Education/OrionTourCenter/meissa.html]Meissa[/url]) nebula at the far left, near Orion's head. Of course, the Orion Nebula and bright stars are [url=http://apod.nasa.gov/apod/ap030207.html]easy to see[/url] with the unaided eye, but dust clouds and emission from the extensive interstellar gas in this [url=http://apod.nasa.gov/apod/ap070106.html]nebula-rich[/url] complex, are too faint and much harder to record. In this mosaic of broadband telescopic images, additional image data acquired with a narrow [url=http://apod.nasa.gov/apod/ap051223.html]hydrogen alpha[/url] filter was used to bring out the pervasive tendrils of energized atomic hydrogen gas and the arc of the giant [url=http://apod.nasa.gov/apod/ap060417.html]Barnard's Loop[/url].

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