All-sky Hydrogen-alpha map

[selden]

Here's a multi-view image showing a few regions from a map of the entire sky showing all the gas clouds glowing with the light of ionized Hydrogen.


(As usual, this links to a much larger picture.)
This picture shows Sagittarius across the top, the Large Magellenic Cloud at bottom left, and Orion at bottom right.

A 6MB zip archive containing the map (a "4K" 10MB DDS file) is now available at http://www.lns.cornell.edu/~seb/celestia/h-alpha_v1.zip.

See http://www.lns.cornell.edu/~seb/celestia/billboard.html#7.2.2 for details.

[Psykotik]

Selden, this one is very astonishing ! Browsing around the nebula rose the room's heat !

Very nice work, many thanks.

[selden]

Psykotik,

Thanks for the kind words.

I have to admit that I'm not all that happy with the colors of the translucent image. I'll try to improve them for v.2

[Buzz]

Hi Selden,

I really like your spheres! The first one (mw-msx) worked, but I can't get the second one (h-alpha) to work unfortunately. I tried all kinds of changes and checked everything I could think of. I have winME, GeForce 2GTS 32MB and Celestia 1.3.1 pre 9. Do you know of any lmitation with this setup that would prevent it from working?

[selden]

Buzz,

Is there any chance you have "Render Galaxies" turned off?
It needs to be on in order to see "Deep Space Objects".
I just tested it with both pre9 and pre11 on my system at work and it seems OK. After I first scared myself because I had "Render Galaxies" turned off myself.

Try typing a "u".

[Buzz]

Thanks for the suggestion Selden, but this was not the cause...

[selden]

Buzz,

Then I suspect it's because of the size of the surface texture files.
Check in the .dsc file to see which of the two Mesh lines is enabled.

Code: Select all

   Mesh "h-alpha.3ds"    # translucent map
#   Mesh "h-alpha-a.3ds"  # opaque map


h-alpha.3ds specifies the texture file named "h-alpha.*"
h-alpha-a.3ds specifies the texture file named "h-alpha-a.*"
The ZIP archive has h-alpha.dds and h-alpha-a.jpg

Unfortunately, the JPEG image in the addon zip archive is a "4K" surface texture map, so it needs about 32MB of graphics memory just for itself.
The DDS texture file also is a 4Kx2K image, but is about 11MB. My belief is that you only need 11MB of graphics memory for that texture and that GF2 cards can use DDS textures. I could be wrong, though.

I picked 4K sizes because that's the biggest I can build on my system without paging. I hadn't thought about the problem that causes for smaller graphics cards. Sorry My previous textures were 2K (8MB) or smaller. Unfortunately, virtual textures don't work (yet?) for Nebula objects.

I've generated some scaled down versions of the JPEG image:
http://www.lns.cornell.edu/~seb/celestia/h-alpha-1k.jpg
http://www.lns.cornell.edu/~seb/celestia/h-alpha-2k.jpg
The 1K version should need only 2MB of memory, 2K = 8MB of memory.

Please try these and let me know if they work for you. If they don't, then the problem is somewhere else.

[Buzz]

Hi Selden,

Thanks a lot for your help! It seems I can use textures up till 2k with my 32MB card. I did try with a smaller jpeg yesterday, but somehow it didn't work. Anyway, I'm enjoying the view! And I think I have to change your Messier texture sizes too.

Buzz

[selden]

Buzz,

My "Messier Other" images are all 512x512. That's 0.5x0.5x4 = 1MB x 16 images = 16MB. They should fit, I think, so long as there aren't very many other textures loaded into your graphics card.

You might want to consider (temporarily) disabling Celestia's "medres" solar system textures. The lores textures should be OK since you're looking at other things. You can rename the folder Celestia\textures\medres to be something else so Celestia can't find it. \textures\nomedres\ might be appropriate


Does this help?

added later:
If you want to look at the Messier pictures against the backdrop of an all-sky image, that will fail because Celestia loads the all-sky image after it loads the other pictures. As a result, Celestia draws the large image in front of all the other deep sky pictures, so it is all you can see.

To be sure you can see them together, add the definition of the all-sky "Nebula" to the begining of messier_other_v2.dsc. That forces Celestia to draw the all-sky picture first and then the other pictures are drawn in front of the all-sky image.

[Buzz]

Hi Selden,

The Messier objects work now too, though I don't know why...
I was inspired enough to make something myself: I took Axel Mellingers partial visible light milky way panorama (http://home.arcor-online.de/axel.mellin ... n45_c.html), flipped it horizontally and put it in a 2k*1k file and renamed it to fit the file name of your model. It is a bit low res, but nice. I checked its orientation by switching on the constellation lines and checking with the constellations that are in the picture; it fits very well! I don't want to post the picture though because of copyright...

Bye,
Buzz

[selden]

Buzz,

I think the Messier pictures worked because you didn't look at anything else first, so there was still enough memory avaiable.

Did you use the sphere from the mw-msx map or the one from the h-alpha map? I think the h-alpha sphere is wrong by 90 degrees, but the mw-msx sphere should be correct.

You're right about the copyright. I wrote to him a while ago asking if a copy could be made available for Celestia, but he never answered

[Buzz]

I used the mw-msx, by coincidence really. And indeed, if only we could get a copy of the complete panorama...

[Buzz]

Hi Selden,

I have been trying to inflate your planetarium sphere to the size of the observable universe with the WMAP background radiation as a texture. This would also show the relative distance to the nearby galaxies.
It does work more or less, but unfortunately the parts of the mesh are starting to get "detached" if the sphere is getting too big, maybe because of computational limitations. Can you tell me if that is the reason?

[selden]

Buzz,

Celestia does seem to have problems with really large distances

e.g. I can't get much further than about 10,000,000,000,000 ly from M31. Beyond that, the distance wraps around to a smaller one.

Also, the largest all-sky sphere that gets drawn for me is has a radius of about 1.9e+19. (2.0e+19 doesn't get drawn).

Can you provide more details about the problem you're seeing?
Please provide the DSC file you're using and a Cel://URL for an appropriate viewpoint when it messes up.

[selden]

I think I managed to duplicate the problem on my system. Large objects have problems.



This is seen using the Cel:// URL that Frank provides on the very first page of the Celestia v1.3.1 User's Guide!

Here's the DSC file that I used.

Code: Select all

# H-alpha full sky map
#
#Derived from the combined Virginia Tech Spectral line Survey (VTSS)
# and the Southern H-Alpha Sky Survey Atlas (SHASSA)
#  by Douglas Finkbeiner et al.
#
# modified for use with Celestia by S.Ball 19Sep03
#
# According to the NASA SkyView Web site, the original map is in the public domain
# see http://skyview.gsfc.nasa.gov/cgi-bin/survey.pl#halpha_co
# I could find no copyright statements on the H-alpha site.
#
Nebula "H-alpha" {

#   Mesh "h-alpha.3ds"    # translucent map
   Mesh "h-alpha-a.3ds"  # opaque map

    Axis [-0.409897 0.623875 0.665406]
   Angle 217.369
   RA 17.76033
   Dec -28.936172
   Distance 2
   Radius 2.0e+19
   InfoURL "http://astro.princeton.edu/~dfink/halpha/"

}

Note the large radius.

System:
512MB 2.4GHz P4, WinXP Pro Sp1
128MB FX 5200, Det. 44.03

[Buzz]

Indeed, this looks a bit like what I see! I took your mw-msx and increased the radius to "only" 10,000,000 ly, and it starts to show wedge-like holes and some flashing parts... 1,000,000 ly is not a problem. Maybe someone knows what is going on. It would be nice to be able to have a 13,7 billion ly sphere