Celestia Forums

Is there a way to have distance always display in light years instead of kiloparsecs no matter how far out I am?
I always think in terms of light years instead of parsecs and kiloparsecs.

Reiko wrote:I always think in terms of light years instead of parsecs and kiloparsecs.

So do i. I rarely move so far away from the solar system that the numbers becomes meaningless... So i much prefer lightyears.

- rthorvald

Lightyears would be more "imagineable". I know the universe is about 13 bilion Lightyears wide. I have no idea how much parsecs these are. Im generally missing an options menu in celestia. For distances (how far kilometers, aus, lightyears ...) and for stadard options, like resolution (could be move to options menu) and a reset to defaul button would be nice (field of view, magnetude ...).

I hope i didn't stray from subject to far away.

I was asking this too, distances in LY and in kpsc.

a preference would be best, i think...but barring that, if anyone knows where to tweak what in the code, i can change it when i compile next

rthorvald wrote:

Reiko wrote:I always think in terms of light years instead of parsecs and kiloparsecs.

So do i. I rarely move so far away from the solar system that the numbers becomes meaningless... So i much prefer lightyears.

- rthorvald

Runar,

the difference is only a factor of 3.26, anyhow. Yet 'parsec' is the unit that is uniformly used by professional astronomers/astrophysicists/cosmologists.

Bye Fridger

Fridger,

the LY is much easier to understand and to visualise. For the students, this is a must. Celestia should show BOTH informations.

Cham wrote:Fridger,

the LY is much easier to understand and to visualise. For the students, this is a must. Celestia should show BOTH informations.

I don't really agree as to intuitiveness. LY is NOT a good unit as to precision, as you sure know. On the other hand, 1 parsec stands for

parallax of one arcsec

It is based on the method of trigonometric parallax, one of the most ancient and standard methods of determining stellar distances.

The actual, exact length of the light-year depends on the length of the reference year used in the calculation, and there is no wide consensus on the reference to be used. Therefore, the light year [ly] is mainly used by Newspapers and popular science magazines, since it "appears" to be more intuitive at first.

If we print out both, the default text output gets longer and longer. How about doing this with the overlay feature in educational versions?

Bye Fridger

Fridger,

in ALL introductory classes to astronomy, we, teachers, are using LY. Not parsecs. So, since Celestia is mainly used in schools, LY should be shown in Celestia. Whatever your opinion on this, this is a fact of life. Period.

Cham wrote:Fridger,

in ALL introductory classes to astronomy, we, teachers, are using LY. Not parsecs. So, since Celestia is mainly used in schools, LY should be shown in Celestia. Whatever your opinion on this, this is a fact of life. Period.

A consequence of the fact that "you, teachers" are uniformly using the LY in school is precisely that people ignore the sensible unit of astronomical distances [pc] and retain the LY for the rest of their lifes...

Also in most american schools inches rather than meters are still used....which I do not find convincing at all.


Bye Fridger

Cham,

Displaying distances in [ly] could be done with simply adding one single Lua file in your extras folder. You wouldn't have to use the whole Lua Edu Tools stuff. As I know that you're interested in it, you could do the same with the display of RA/Dec, for example...

As ElChristou suggested to me, I'm thinking about releasing some of the features of the Lua Tools separately. This way, users could make their own setting, by simply adding the relevant files in the extras folder. Do you (and other users) think it is worth spending time on this ?

Vincent,

Yes, I think it would be a worthwhile project.

Notwithstanding the parsec versus LY argument, I think it would be a useful feature to allow user control over ANY displayed units, at any time, within reason. (This could be a toggle thru the different distance scales from metres -> km -> AU -> LY -> parsecs -> kPc -> MPc ) Have I missed any???

BTW. Velocity as well as distance should be also expressed in the specified units. eg. m/s -> km/h or km/s, etc...

This would allow both the purists and the plebsto be happy, making the argument superfluous.

Chuft-Captain wrote:Notwithstanding the parsec versus LY argument, I think it would be a useful feature to allow user control over ANY displayed units, at any time, within reason. (This could be a toggle thru the different distance scales from metres -> km -> AU -> LY -> parsecs -> kPc -> MPc ) Have I missed any???

BTW. Velocity as well as distance should be also expressed in the specified units. eg. m/s -> km/h or km/s, etc...

This would allow both the purists and the plebsto be happy, making the argument superfluous.

How about printing out radii of celestial objects in miles? After all this unit is still used a lot in American/British schools and daily life. Right?


Bye Fridger

t00fri wrote:
How about printing out radii of celestial objects in miles? After all this unit is still used a lot in schools and daily life. Right?


Bye Fridger

In France, I (and all people ) never use miles but meters (in school or in daily life)

t00fri wrote:How about printing out radii of celestial objects in miles? After all this unit is still used a lot in American/British schools and daily life. Right?

Bye Fridger

Why not feet or inches?

Seriously though, SI units should be the default wherever possible, however I see no good reason to prevent users from selecting their units of preference (at least for display purposes) where possible.

So, I decided to put in nanometer for all distance and we will have a lot of zeros in the screen, beautiful ?

Actually, from the perspective of an addon creator, there are situations where one might like to be able to accurately position an object defined in an STC file at the same location as another object defined in an SSC file, however the distance units used for STC objects are different to those used in SSC files.
This means we have to work out the conversion factors used by celestia between units.
In this circumstance it would be very convenient if Celestia could toggle between different units and give the correct conversion factor.

EDIT: Actually, from a creators viewpoint it would be more useful to be able to specify the units in the STC or SSC file. eg. Even in SSC's where the parent object is a star, semimajor axis must apparently be defined in AU's; whereas when the parent object is a planet, then it's Km's.

For argument's sake, let's say I wanted to place a Black Hole (defined in an SSC file), at the center of a Moon (which is defined in an SSC).

Please remember that Lua/CelX is a general purpose programming language. It seems to me that providing a units conversion popup would be a reasonable project for someone who would like to learn more about Celx scripting.

t00fri wrote:the difference is only a factor of 3.26, anyhow. Yet 'parsec' is the unit that is uniformly used by professional astronomers/astrophysicists/cosmologists.

While i understand your need for accuracy, and so the preference for parsecs, to me it is just confusing... Because light-years gives me a sense of where i am (no matter how illusory the feeling is, since one really can??t grasp the scale of even a light-year), it still is a clue i can orient myself by. Parsecs i have no gut feeling about at all.

It seems to me the optimal solution would be the ability to toggle between the two. Maybe one could set the option in the config file, with parsecs as default to cater to the science purists like yourself

- rthorvald