AM0644-741 add-on

[DaveMc]

Inspired by the latest Hubble image of the Lindsay-Shapley Ring Galaxy (AM0644-741), I made this very simple billboard add-on (using Selden's billboard model) which can be downloaded here:

http://celestiamotherlode.net/creators/davemc/AM0644-741.zip

Here's a screen shot:


The orientation is about 90 degrees CW from the published Hubble image but seems to *almost* match the images I've seen from ground telescopes, please feel free to correct me on this. It *almost* matches because this was as close as I could get before Celestia's orientation edit mode drove me nuts!

Dave

[selden]

Dave,

I haven't checked its orientation yet, but... If one starts from the orientation provided by Grant Hutchison's spreadsheet, in principle all one has to do is rotate the model using the right-mouse-button. That's not quite so crazy-making as trying to do all three rotations.

[DaveMc]

Hi Selden,

I was hoping you would respond to this. I did start with Grant's spreadsheet but the coordinates from it were off in x,y, and z.

Another thing, for some reason the edit mode left mouse-right mouse procedure doesn't seem to work nearly as well in Celestia 1.3.1-1 as it did in 1.3.0., at least to me.

A third thing, when I restarted Celestia about an hour later and went back to AM0644-741 to check something the orientation was different! I have my start.cel set to open Celestia at Earth (Seattle) and set the initial orientation from there. I also went directly to AM0644-741 from there on the recheck. When I started from somewhere on the east coast, the orientation was different again. Start from someplace in the southern hemisphere, again different. Does this make sense?

When I get the time I'm thinking I just need to start over from scratch.

Thanks,
Dave

[selden]

Dave,

You mention "went back to AM0644-741". I hope you don't mean "GoTo".

Because it's so far away, the orientation and position of any DeepSpace Nebula can be adjusted from any viewpoint inside the solar system. When Celestia stops travelling to its initial viewpoint, I usuallly
Select the Nebula,
Track it,
enable Celestial Grid,
rotate the viewpoint so the top of the screen is North, and then I
increase Celestia's telescopic magnification by holding down the "." key until the Nebula fills the field of view.

Then I start making adjustments.

[granthutchison]

Dave:
Not sure why you've had a problem with my spreadsheet. Plugging in the RA and Dec from your dsc file, as follows:

Code: Select all

   RA 6.71836
   Dec -74.23694

I get these arguments for Axis and Angle:

Code: Select all

   Axis       [0.9956 -0.0316 -0.0886]      
   Angle      172.355

This aligns the billboard neatly with Earth, ready for rotational tweaking.

Grant

[DaveMc]

Hi Guys,

Selden,
Duh, that's exactly what I was doing. I haven't done this for a while and was relying on memory - bad move. I'll reset it the proper way!

Grant,
I'll plug the numbers back into your spreadsheet just to make sure I didn't mess up the RA and/or Dec input. I suspect the problem was, as Selden suggested, I was doing the alignment wrong in the first place.

Thanks!
Dave

[DaveMc]

OK, the AM0644-741 orientation should now be correctly North-South aligned. Hopefully it's right this time. Here's the new dsc code:

Code: Select all

Axis [0.848185 0.015244 0.529481]
Angle 172.355

I also added background transparency to the .png texture file.

http://celestiamotherlode.net/creators/davemc/AM0644-741.zip

Dave