how do I view the sun as I'm standing on earth?

[rookie37]

I'm new to Celestia. Can I plot an analemma with it? I want to draw a figure 8 and bring it into photoshop.

[Fenerit]

Not sure of this; just a midnight replay after concert. At noon in your location, let center on the sun and synchronize it. Do bookmark the situation. Open the solarsys.ssc and set the Earth's rotation = 0. Restart Celestia and take up the bookmark. Do increasw the turns ("L" key). About Photoshop, maybe you must work on situation's screendumps (layer's propriety "add" or "screen" or "darken").

EDIT LATER:
be sure that the horizon be visible through the FOV.

[Hungry4info]

Open the solarsys.ssc and set the Earth's rotation = 0.

Don't you need to not set it at all or define a synchronous rotation? Zero would still lead to the sun going across the sky (once per year).

[Fenerit]

Open the solarsys.ssc and set the Earth's rotation = 0.

Don't you need to not set it at all or define a synchronous rotation? Zero would still lead to the sun going across the sky (once per year).

Right. No synch.

[abramson]

My suggestion is to use a planetarium program instead, which is better suited than Celestia for these tasks. In Stellarium you advance by 1 solar day with the key = (and receed with -, or by solar weeks with [ and ]). Keep pressed and you'll see a beautiful analemma. You can't track the path, though (at least I am not aware how to do it). In Cartes du Ciel, choose "day" from the drop box of time increments, and press the animation button. (Better, set something like 7 days for faster animation.)

(Edited for errors)

[rookie37]

Can you recommend some planetarium software?

[abramson]

As I said, Stellarium and Cartes du Ciel. Stellarium is very realistic. Cartes du Ciel is better to plan an observing session and to use at the telescope.

For the analemma, I would say Stellarium. Just set the time to local noon, face the sun, choose a wide enough field of view and press ] (or [) to add (or substract) a solar week until you are content. You can save snapshots with ctrl-s, they automatically get a file name with increasing numbers.

NOTE: My explanation in a previous message was wrong. You need to change by 1 solar day, week, etc (not sidereal). I have edited the message. I apologize.

[Marco Klunder]

My suggestion is to use a planetarium program instead, which is better suited than Celestia for these tasks.

Hello,

Yes I like Stellarium too, but for this "analemma simulation" Celestia is very well occupied

Take the following (example) script and run in Celestia:

Code: Select all

-- CELX Initialisation
celestia:setrenderflags{orbits=false, cloudmaps=false, cloudshadows=false, constellations=false, galaxies=false,
                        planets=true, stars=true, nightmaps=false, eclipseshadows=false, ringshadows=false,
                        comettails=false, boundaries=false, markers=false, automag=true, atmospheres=true,
                        grid=false, smoothlines=false, lightdelay=false, partialtrajectories=false, nebulae=false,
                  openclusters=false, globulars=false, ecliptic=false, equatorialgrid=false, galacticgrid=false,
                        eclipticgrid=false, horizontalgrid=true}

sun=celestia:find("Sol")
earth=celestia:find("Sol/Earth")
celestia:settimescale(0)
obs=celestia:getobserver()
obs:setfov(math.rad(110))

-- Define position on Earth (Latitude/Longitude in degrees)
lat_earth  = 52.3833              -- Latitude in degrees
long_earth = 4.9                  -- Longitude in degrees

-- Goto position on Earth surface, center the Sun and set initial data/time
obs:gotolonglat(earth, math.rad(long_earth), math.rad(lat_earth), earth:radius()+1, 0, celestia:newvector(0,1,0))
obs:synchronous(earth)
wait(0)
obs:gotosurface(earth, 0)
wait(0)
tdb_juliandate = celestia:utctotdb(2011, 8, 3, 10)
celestia:settime(tdb_juliandate)
obs:center(sun, 0)
wait(0)

--Analemma Routine
for i=0,2000 do
   tdb_date = tdb_juliandate + i
   celestia:settime(tdb_date)
   wait(0.025)
end

The analemma drawing itself, however is not present, but the simulation very well shows the analemma.
You can change longitude and latitude and corresponding UTC time for the local noon yourself of course, as well as playing with the FOV.

Marco

[abramson]

Agreed: you can do it in Celestia, using your script or one that rookie37 (new to Celestia) might learn to program himself, thus becoming more knowledgeable both in Celestia and in the art of programming.

Or, rookie37 can launch Stellarium and press ]. I will say no more.

[rookie37]

NOTE: My explanation in a previous message was wrong. You need to change by 1 solar day, week, etc (not sidereal). I have edited the message. I apologize.

No appology needed. If fact it makes my embarresment a little easier. I skimmed over your first email and didn't see that you already made a suggestion for software