Coordinate conversion

[Reiko]

Can somebody please tell me the formula to type into mathmatica so I can convert RA and Dec into the coordinate format celestia uses?
I know there are online converters to use but I need something that works offline.

Thank you

[selden]

For stc objects, Celestia uses fractional degrees instead of hours.
I don't know if this is the format that Mathematica uses, but...

RA = 15 * (hours + minutes/60 + seconds/3600)
Dec = sign * (degrees + minutes/60 + seconds/3600)

For dsc objects, Celestia uses fractional hours:
RA = hours + minutes/60 + seconds/3600

Does this help?

[Reiko]

Yes that help thank you much. I can now convert the coordinates on my calculator.

[PlutonianEmpire]

What I do is use Google Earth. It works offline, but won't load new images. You can go to Tools>Options, then in options, under "show lat/lon", select "Degrees, minutes, seconds", then select "ok", and create a placemark and put in the lat/lon coordinates that you desire. The lat/lon coordinates also work for Google Earth Sky. Then go back to the options dialog box, and switch the "show lat/lon" option to "Decimal Degrees". click "ok", and right-click on your new placemark in the list of placemarks, and select "properties". You should now see the numbers in Celestia Format.

Unfortunately, this only works for .stc files.

Anyway, I hope this helps.

[selden]

Tch,

I'm surprised nobody commented on my serious error in all of the formulas.

the Multiply (*) should be replaced by a Divide (/)

I'll do that now.

s.

[Chuft-Captain]

Tch,

I'm surprised nobody commented on my serious error in all of the formulas.

the Multiply (*) should be replaced by a Divide (/)

I'll do that now.

s.

Sorry Selden,

For timezone reasons I didn't have the opportunity to see your error before you corrected it. (ie. I was asleep).
Given more time, no doubt, I would have commented.

[Reiko]

Tch,

I'm surprised nobody commented on my serious error in all of the formulas.

the Multiply (*) should be replaced by a Divide (/)

I'll do that now.

s.

It took me a while to figure that out after noticing the huge numbers I was getting.

[tesseract]

Folks,

I'm still having trouble with the basics ... can't move to a desired RA and DEC location. I know how to convert RA hours/minutes/seconds to degree format or nom. E.g., 2h30m16.3506s = 37.5681275 degrees or 2.5045418333 nom. I know how to convert DEC as well. E.g., 44deg 48' 24.207" = 44.806724267071 degrees.

I am specifically referencing the CELESTIAL coordinates RA and DEC used to plot objects in the sky. I am not referencing the TERRESTRIAL/GEOGRAPHIC coordinates (longitude and latitude) used to plot locations on the Earth's surface.

My problem is that, when I enter either the degrees or nom, it does not take me to that RA/DEC position of the sky.

Example problem --
I have the Celestia Time frozen at a given date -- e.g., October 31, 1999.
My location is 1.25 AU from the surface of the star, Vega.
My GO-TO entry: Lat = 44.80672, Long = 37.56813.
My desire was to see the sky at the associated RA and DEC (e.g., 2h30m16s and +44.80672). The image sweeps to a completely different RA and DEC location.

Another Example -- 0.75 AU from star 85 Peg Aa. Date of October 1960. Entry of Lat = 0, Long = 0.
The GO-TO sweeps and stops at RA and DEC (approximate) 2h 7m 59.789s, +12deg 56' 19.5".

How do I go to a desired Celestial Coordinate position for any given location? What do I need to enter in the Lat and Long fields? Decimal or Nom conversions don't seem to work. If I have to use Earth-based Terrestrial Coordinates, it would be very difficlut to translate since the variance changes as the Earth rotates and revolves.

I apologize if this question has been asked and answered by others in the past -- but I did a search and did not find this issue.

Tesseract

[selden]

Longitude and latitude are relative to the object currently Selected. In order for them to be related to RA and Dec of the Equatorial coordinate system, Earth must be Selected.

The latitude and longitude for any other object have no relationship to RA and Dec: longitude is relative to some arbitrary surface feature and latitude is relative to the object's own rotational axis. When those values are unknown, Celestia arbitrarily gives them values relative to the Ecliptic coordinate system, which is tilted relative to the Equatorial coordinate system.

In order for the Earth's latitude and longitude to be easily translated to RA and Dec, Celestia's simulated time must be stopped and its date must be set to a date when 0 degrees of Longitude points toward 0h of RA. A time near the Vernal Equinox of the year 2000 might be appropriate, since that's what's used as the basis for the currently accepted Equatorial coordinate system.

Here's a URL for one such time for Celestia v1.6.0:

Long,Lat = RA,Dec