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Q: Calculating exact Longitude from Right Ascension 19h 1m 22s? ( No Answer,   3 Comments )
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 Subject: Calculating exact Longitude from Right Ascension 19h 1m 22s? Category: Science > Astronomy Asked by: cnwells-ga List Price: \$55.00 Posted: 26 Dec 2005 11:05 PST Expires: 02 Jan 2006 15:05 PST Question ID: 609853
 ```This calculation is to explain and calculate how Right Ascension 19h 1m 22s can be converted into longitude. In case additional information is needed, this calculation is used to find the location where the Earth & Sun at the closest point together, called a perihelion which will be on January 4th 2006 at 15:30 UT per NASA. The answer which was provided is Right Ascension 19h 1m 22s, Declination -22degrees 41.5 hours (reference: http://www.fourmilab.ch/cgi-bin/uncgi/Solar). I know that declination = latitude however the question is how to calculate the longitude which is listed as Right Ascension 19h 1m 22s? The answer should show: 1. How to arrive at the calculation 2. Credentials of answerer 3. Any links to provided to referenced websites.``` Request for Question Clarification by welte-ga on 26 Dec 2005 15:03 PST ```Hi cnwells-ga, Just to clarify, as you likely know, right ascension is analogous to longitude with respect to the celestial sphere. Are you trying to find out which point on the Earth will be closest to the sun at the perihelion you mention? -welte-ga``` Clarification of Question by cnwells-ga on 26 Dec 2005 17:21 PST ```That is correct, I am looking for this closest point and the answer that I have been provided for the closest point was RA 19h 1m 22s and declination -22 degrees 41.5 hours. The goal is to transform this into a location on the earth. Since declination maps directly to latitude, now I just need longitude to find this location. Your help is greatly apprechiated.``` Request for Question Clarification by welte-ga on 31 Dec 2005 09:43 PST ```Hi again, I think that the simple approach that Myoarin mentions is the easiest way to tackle this problem (i.e., where on the Earth is the sun directly overhead at the time you specify). I haven't verified his calculation. Is there any other information you'd like? -welte-ga```
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 ```Your question makes no sense. The Latitude and Longitude are arbitrary and given right there on the link you specified. You can set them to whatever you like.```
 ```IF I understand correctly, then you are looking for the spot on earth (Lat. and Long.) that at 15:30 UT is at solar noon (3 1/2 hrs east, ca. 52° 30' long. east, corrected for whatever adjustment may be necessary), and the declination of 22° 41' 30" lat. south. (That is my notation of your "-22 degrees 41.5 hours", since I believe you mean 41.5 minutes). That would be east of southern Madagascar. Is that close enough - without adjustment - since NASA provides only 15:30 UT, which seems an unusually "round" figure? Regards, Myoarin```
 ```The timezone method actually puts you in Southern Brazil, 12:30pm local time which is where I am (searching for the location). However, I need the calculation based off the Right Ascension per an astronomer to find the exact location. Thank you for your help.```