Here comes two minor questions (bugs)?
1 It seems that many of the extrasolar planets has their day lenght set to 10.000 hours. Is that really correct? I guess the day-information for most of those planets isn?t known yet. So why don?t set the day to "Unknown" instead?
2, When right-clicking on "Sol" and selecting "Info" an 404-page appear saying "Error message - This identifier is not present in the database: HIP 0". Is this an invalid URL in Celestia or a miss in the Extra-solar Planets Catalog?
I?m running Celestia 1.3.1 on a Win ME-machine.
Two minor things from a complete beginner...
The 10 hours value is based on rotation speeds of the gas giants in our solar system, there is no way to specify "unknown", so 10 hours is a plausible guess. In the most recent version of extrasolar.ssc, (available from the CVS tree), spindown calculations have been incorporated to simulate tidal braking, presumably from an initial estimate of 10 hour rotation period.
The second point: "HIP 0" is not an official designation. Celestia uses the Hipparcos catalog as the basis for the data structure used to store the stars in memory, so stars not in the Hipparcos catalog have to be assigned fake numbers.
The Hipparcos catalog was produced by a mission to measure the distances to a selection of stars by measuring the change in angle relative to the distant background when the Earth is at opposite ends of its orbit. Since the distance to the Sun cannot be calculated in this way, and since its distance can be found more accurately by other methods, and the brightness of the sun is probably not good for the instruments on the Hipparcos spacecraft, the Sun is not in the Hipparcos catalog.
The sun is thus assigned a fake number of 0. When Info is selected for a star, a query is sent to an astronomical database with the Hipparcos number of a star. Since HIP 0 does not actually refer to any real star, but is used as a convention by the programmers to incorporate the sun into the software, the astronomical database will produce an error message, as it contains only real stars and the real references to them.
The second point: "HIP 0" is not an official designation. Celestia uses the Hipparcos catalog as the basis for the data structure used to store the stars in memory, so stars not in the Hipparcos catalog have to be assigned fake numbers.
The Hipparcos catalog was produced by a mission to measure the distances to a selection of stars by measuring the change in angle relative to the distant background when the Earth is at opposite ends of its orbit. Since the distance to the Sun cannot be calculated in this way, and since its distance can be found more accurately by other methods, and the brightness of the sun is probably not good for the instruments on the Hipparcos spacecraft, the Sun is not in the Hipparcos catalog.
The sun is thus assigned a fake number of 0. When Info is selected for a star, a query is sent to an astronomical database with the Hipparcos number of a star. Since HIP 0 does not actually refer to any real star, but is used as a convention by the programmers to incorporate the sun into the software, the astronomical database will produce an error message, as it contains only real stars and the real references to them.
Thanks!
... For the detailed answer. Now I understand what?s it all about 
Well. But, if the sun don?t exist in the star-database, there is actually another way to get an valid info-link.
The planets, moons and other objects in our solarsystem are linked to another site, http://www.nineplanets.org/. On that site they also have a page about the sun. Wouldn?t it be better to change the suns info link from the non-existing HIP-number to the working http://www.nineplanets.org/sun.html? Or is that impossible by some programming-reason?
Maybe this is just a little detail, but I think it feels a bit silly when I?m able to get information about stars hundreds of lightyears from us but just encounter an "404-error" when reaching for info on our own sun.
/ Observer (formerly known as unregistered "Tobbe the Newbie!").
Well. But, if the sun don?t exist in the star-database, there is actually another way to get an valid info-link.
The planets, moons and other objects in our solarsystem are linked to another site, http://www.nineplanets.org/. On that site they also have a page about the sun. Wouldn?t it be better to change the suns info link from the non-existing HIP-number to the working http://www.nineplanets.org/sun.html? Or is that impossible by some programming-reason?
Maybe this is just a little detail, but I think it feels a bit silly when I?m able to get information about stars hundreds of lightyears from us but just encounter an "404-error" when reaching for info on our own sun.
/ Observer (formerly known as unregistered "Tobbe the Newbie!").
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granthutchison
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I don't believe it's possible to assign a custom InfoURL to a star in the current version of Celestia - though (along with the ability to customize other features of individual stars) this would seems like a useful addition for future version.
As to the rotation periods: a while back Chris and I had some discussion about flagging estimated figures in the display. My own idea was to have two levels of "estimate flag":
A trailing "?" would indicate an estimate based on simple assumptions: the radii of many minor moons are deduced from their measured brightness and a plausible assumed albedo - so they'd merit this sort of mark. Celestia's calculated planet temperature would also merit a single query mark, as would the radii and temperatures of distant stars.
A trailing "???" would indicate something that's no more than a vaguely ballpark figure: the rotation periods of most minor moons, and the radii and rotation periods of extrasolar planets, for example.
Anyone have any thoughts on that?
Grant
As to the rotation periods: a while back Chris and I had some discussion about flagging estimated figures in the display. My own idea was to have two levels of "estimate flag":
A trailing "?" would indicate an estimate based on simple assumptions: the radii of many minor moons are deduced from their measured brightness and a plausible assumed albedo - so they'd merit this sort of mark. Celestia's calculated planet temperature would also merit a single query mark, as would the radii and temperatures of distant stars.
A trailing "???" would indicate something that's no more than a vaguely ballpark figure: the rotation periods of most minor moons, and the radii and rotation periods of extrasolar planets, for example.
Anyone have any thoughts on that?
Grant
I did a feature request on this some time ago. But it seems to be rare that anyone reads these requests thought :shrug:granthutchison wrote:I don't believe it's possible to assign a custom InfoURL to a star in the current version of Celestia - though (along with the ability to customize other features of individual stars) this would seems like a useful addition for future version.
granthutchison wrote:As to the rotation periods: a while back Chris and I had some discussion about flagging estimated figures in the display. My own idea was to have two levels of "estimate flag":
A trailing "?" would indicate an estimate based on simple assumptions: the radii of many minor moons are deduced from their measured brightness and a plausible assumed albedo - so they'd merit this sort of mark. Celestia's calculated planet temperature would also merit a single query mark, as would the radii and temperatures of distant stars.
A trailing "???" would indicate something that's no more than a vaguely ballpark figure: the rotation periods of most minor moons, and the radii and rotation periods of extrasolar planets, for example.
Anyone have any thoughts on that?
Increasing numbers of `?` for increasing levels of uncertainty is not a bad idea. I would supply an additional +/- value range where possible.
maxim