Astro Art

geckzilla · Post by **geckzilla** » Sat Jan 31, 2015 1:50 am

Nitpicker wrote:That shape doesn't look right to me.

The parameters for the ellipsoids are tabulated here:
http://asterisk.apod.com/viewtopic.php? ... 1&start=38

I'm afraid I don't know enough about your simulation software, to comment on what parameters it needs.

The tip comes to a sharp point because there aren't enough polygons to go around up there. Blender doesn't give a rat's ass about the speed of light so the best I can do is create a shape that approximates the time the light sphere becomes visible to humans. I'm not sure how to translate your table into a shape.

Nitpicker · Post by **Nitpicker** » Sat Jan 31, 2015 4:12 am

geckzilla wrote:
Nitpicker wrote:That shape doesn't look right to me.

The parameters for the ellipsoids are tabulated here:
http://asterisk.apod.com/viewtopic.php? ... 1&start=38

I'm afraid I don't know enough about your simulation software, to comment on what parameters it needs.
The tip comes to a sharp point because there aren't enough polygons to go around up there. Blender doesn't give a rat's ass about the speed of light so the best I can do is create a shape that approximates the time the light sphere becomes visible to humans. I'm not sure how to translate your table into a shape.

What sort of commands do you have for shapes or surfaces or profiles? (I'm afraid I don't understand what the fat teardrop is supposed to represent at all and I can't figure the orientation.)

One "simple" way to make the surface of a prolate spheroid (which we'll need for each echo shell) is to start with a semi-circle with a radius equal to the semi-major axis, which starts and ends on the major axis of the desired prolate spheroid. You then re-scale the semi-circle in the direction of the minor axis, by a factor of {[minor axis]/[major axis]}. You then revolve the resulting half-ellipse 360 degrees around the major axis, to create a surface of revolution that is the finished product. Can you do that in blender?

geckzilla · Post by **geckzilla** » Sat Jan 31, 2015 4:18 am

Yes, what you are talking about is frequently used to create wine glasses, vases, etc. It can be done. My hangup is doing it more or less "right" and that I am a relative newbie with it. The teardrop was my guess at the shape of a light sphere as it appears distorted from a human perspective... the front arrives much sooner than the back. It's all bollocksed up and I need some actual math because this is at the limit of what my brain seems capable of dealing with on its own.

Nitpicker · Post by **Nitpicker** » Sat Jan 31, 2015 4:51 am

The ellipsoid echoes all have two fixed foci: the observer is at one and the star is at the other.

f = half the distance between observer and star = 10,000 light years for V838 Mon

t = time in years since initial observation of star outburst

c = speed of light = 1 light year per year

a = f + c*t/2 = semi-major axis of ellipsoid echo at time t

b = SQRT(a² - f²) = semi-minor axis of ellipsoid echo at time t

Voila.

geckzilla · Post by **geckzilla** » Tue Feb 03, 2015 7:33 am

Couple of Saturns.

Faking the famous portrait by Cassini
http://www.geckzilla.com/astro/saturn_rings_render2.jpg

Behind Saturn
http://www.geckzilla.com/astro/saturn_backlight_sss.jpg

Am rendering an animation sequence to show off some interesting ring optics.

geckzilla · Post by **geckzilla** » Tue Feb 03, 2015 8:01 pm

Here's the render test. Video description:
I should have spent more time getting the camera movements to look good, but this is just a test. This is how it looks straight out of Cycles. Note how the rings darken as the Sun moves behind them and then they almost seem brighter from below. Yes, that little white dot is the Sun. It doesn't have any special camera effects to it so it is just the size of the solar disc as viewed from Saturn.

Click to play embedded YouTube video.

geckzilla · Post by **geckzilla** » Fri Feb 20, 2015 9:03 am

Thing inspired by black holes. Not really anything in particular, though. Just a gradient of increasing index of refraction. The outer edge of the disc has an IOR of 1 while the inside starts at 2 and increases gradually to 350.

Click to play embedded YouTube video.

Ron-Astro Pharmacist · Post by **Ron-Astro Pharmacist** » Sat Feb 28, 2015 6:21 pm

Congrats to Judy for her published reprocessed Hubble mosaic of M82 in April’s S & T. I didn’t understand the caption though? “Judy Schmidt reprocessed this Hubble mosaic of M82 to draw out the background clusters and stippled star field.”

Sue French’s article, Spring’s Hit Parade, pointed out the obscuring dust clouds (of supernovae) but I didn’t see how the image drew out the background clusters? Sue French also mentioned that she sketched M82 for this article on March 18, 2014 but I couldn’t find it?

Any comments on her caption Geck? I’m just curious about Sue’s point and her sketch (was it on the following page?). Again, congratulations – it’s fun to see familiar names when I’m paging through my mags.

I suspect the magazine's image is copyrighted so this is another version of M82 for those curious with respect to my question.

Ron

bystander · Post by **bystander** » Sat Feb 28, 2015 6:58 pm

The gecko's M82 on flickr is here.

: Click to view full size image

geckzilla · Post by **geckzilla** » Sat Feb 28, 2015 8:14 pm

Blink, blink... I had no idea I had a pic S&T this month! When I reprocessed this image I did not have any particular goal in mind. I just wanted to see what I could come up with and to study the object in detail. I find that processing of images gives me a greater understanding of what I'm looking at. There is no one right way to process something. The official press release image (which Ron posted) was processed to focus hard on the hydrogen filaments flowing out of the galaxy. Mine is just a whole lot less aggressively processed and softer. I would say that Sue French's description is just a very general but nicer way to say "She processed the image." The word "stippling" may have come from a comment I wrote on my Flickr page. It's not something you can easily see unless you zoom in very close to the original.

geckzilla · Post by **geckzilla** » Mon May 11, 2015 11:26 pm

Something I did today. This three armed galaxy is a real thing but it is too far away to get a good picture of with current telescopes. Maybe we'll never see a better picture of it. This is my attempt to do one of those artistic impressions.

: Left: Illustration; Right: Hubble image

geckzilla · Post by **geckzilla** » Tue May 12, 2015 2:16 am

Finishing up with the background and minor details. Made using a combination of digital painting and textures from some real Hubble imagery.

geckzilla · Post by **geckzilla** » Mon Jun 01, 2015 8:45 am

This is not art but I don't think I need a new thread just for my astronomy images. This is something I pulled out of the Hubble archive. It's eight frames, each one is a month after the other. The eight frames are played forward and then backward to give the stars a smoother animation. There are some dark spots which are anomalies with the detector (WFC3/IR) but they are fairly easy to ignore. The point is... the Universe is alive.

There is a 4.78 megabyte gif at this link. Be advised.
http://www.geckzilla.com/astro/NGC4258_var_stars.html

I'm going to make a better one later that's in color... this was just a quick run through to see if it would be worth doing. I'm actually astonished at how so many of those dim stars in this galaxy (NGC 4258) pulse.

Starship Asterisk*

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