M51 - Whirlpool Nebula addon (2k)

[jim]

Hi all,

Here is another "billboard" addon - the Whirlpool Nebula (M51) and companion NGC 5195. I've combined a gray scale and color picture and enhanced the texture a bit in Photoshop.



I can't find a pic of M51 with enougth stars therefore I used to align the billboard exact positions of M51 and NGC 5195. If Seldons Messier-addon ('messier_galaxies.dsc') has installed this values for M51 can be corrected:

RA 13.49788
Dec 47.19467

Selden, I noticed several times that accuracy of galaxies can(/should) be improved.

There are two versions for download an my web site available:
2k DDS DXT5: http://www.celestiaproject.net/~jim/files/M51- ... 2k_dds.zip (1,77mb)
1k PNG: http://www.celestiaproject.net/~jim/files/M51- ... 1k_png.zip (727kb)

Bye Jens

[selden]

Jens,

If you can't find a picture with enough stars, you can make one instead.
NASA's SkyView server will generate a picture of any size of any part of the sky, although at relatively low resolution. Messier objects are easy for it.

See http://skyview.gsfc.nasa.gov/ for an introduction to SkyView.
I use the page http://skys4.gsfc.nasa.gov/cgi-bin/skvadvanced.pl to generate alignment pictures. Be sure to read the imformation page about the survey sources at http://skyview.gsfc.nasa.gov/cgi-bin/survey.pl. Some of them, the optical catalog in particular, are copyrighted. Images created from the copyrighted surveys may not be published without the permission of the copyright holders. (but they aren't appropriate for general use with Celestia, anyhow. They aren't pretty enough! )

Unfortunately, it seems that the galaxy.dat catalog files that Paul generated for Celestia v2.4, which are the ones I used to create the .DSC galaxy catalogs, need to have all of their coordinates updated. I'm guessing that their precession to J2000 wasn't done accurately enough. That's not something I can do right away. Sorry.

[marc]

Im confused, its called a nebula but it looks like a galaxy. Which is it?

[selden]

Marc,

1) "Nebula" is the keyword in .DSC files that tells Celestia that a 3DS model ("Mesh") should be displayed. "Galaxy" is the keyword in .DSC files that tells Celestia to draw a "grey blob" that resembles a galaxy.

2) "Nebula" is a generic astronomical term for a dim grey blob in the sky. For a long time telescopes weren't good enough for observers to be able to distinguish between gaseous clouds and distant aggregations of stars. It wasn't until the mid 1800s that many of the nebulae were recognized as "island universes" that were outside our own.

Does this answer your question?

[marc]

Thanks Selden.

Ok, so Whirlpool Nebula is just a historical name and what we are looking at is two galaxies.

Another question, In this image is NGC 5195 behind M51 or are they closer than that and interacting?

[selden]

Marc,

NGC 5195 is behind M51 and they are interacting.