Incorrect albedo in solarsys.ssc?

[Malenfant]

The albedos in the solarsys.ssc don't agree with the values found on the NSSDC planetary datasheets and elsewhere (eg my RASC Observer's Handbook).

Currently they are (in both pre7, the cvs source, and FT1.1):

Code: Select all

Mercury         0.06
Venus         0.77
Earth          0.3
Moon          0.12
Mars          0.15
Jupiter          0.51
Saturn          0.50
Uranus          0.66
Neptune          0.62
Pluto          0.55


IN the NSSDC datasheets (and other 'official' solar system data sources) they are:

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Mercury         0.106
Venus         0.65
Earth          0.367
Moon          0.12
Mars          0.15
Jupiter          0.52
Saturn          0.47
Uranus          0.51
Neptune          0.41
Pluto          0.5 - 0.7


These are visual geometric albedos (the ssc values are also very different from the Bond albedos, but I presume you're using geometric (visual) albedos here). Note though that the values for the Moon and Mars are the same in both the ssc and the NSSDC data.

I haven't checked every single body in the ssc file yet, but certainly it seems to me that these ones should be corrected!

[Malenfant]

Is this a known bug or something? I thought someone would have commented on this by now.

Or was it just a slow weekend?

[selden]

Those values have been there since the beginnings of Celestia: those are the values that are in v1.0.10, the earliest version on SourceForge.

I suspect you'll have to persuade Chris to update them.
I'd suggest posting corrected values to the developers' mailing list.
Be sure to cite a specific source for each of the values you send.

[Malenfant]

Those values have been there since the beginnings of Celestia: those are the values that are in v1.0.10, the earliest version on SourceForge.

I suspect you'll have to persuade Chris to update them.
I'd suggest posting corrected values to the developers' mailing list.
Be sure to cite a specific source for each of the values you send.

OK, Selden. How do I get onto the mailing list?

I'm surprised nobody noticed this difference before (particularly Grant. I thought he updated these ssc files a lot?).

[selden]

http://lists.sourceforge.net/lists/list ... developers

Grant was primarily interested in getting the orientations correct.
The albedo values only affect the brightness of the dot that's drawn when an object is too small to resolve.

[Malenfant]

http://lists.sourceforge.net/lists/listinfo/celestia-developers

Grant was primarily interested in getting the orientations correct.
The albedo values only affect the brightness of the dot that's drawn when an object is too small to resolve.

Well I only noticed it myself because I need the albedo for my planetary magnitudes script.

BTW, can we add our own terms to an ssc? Say for example I wanted a Bond Albedo as well as a geometric one, could I add that to the ssc (as BondAlbedo or something) even though Celestia itself wouldn't use it? Or would the ssc not render because there's stuff in there that Celestia doesn't understand? (just asking out of curiosity, not got anything planned here... )

[selden]

Unfortunately, Celestia will generate an error and stop reading the SSC file if you include a keyword that it doesn't know about. For example, I often insert "exit" in SSC files when I want the stuff after that point to be ignored.

[Malenfant]

OK, so I guess I'd just have to include any extra numbers I wanted in the script itself.

BTW, Celestia does support "Mass" as an entry in the ssc, yes? Can you declare masses for stars and planets, or just stars? And what are the units?

[selden]

You might want to consider including your desired parameters in the catalog file, but have them commented out.

Although Celestia does accept the SSC keyword "Mass", and sets a value named "mass," it otherwise ignores it completely. There is no code using it, so there are no implied units.

[Malenfant]

Well I posted on the developers list a few days ago and have had no response or comment at all. Looks like everyone's gone back to sleep there.

I know Grant pops in occasionally here... Grant? Do these need updating? It seems to me that they do.