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Re: equinox
From: Jay Borseth
Date: 2004 Mar 21, 16:26 -0800
From: Jay Borseth
Date: 2004 Mar 21, 16:26 -0800
I am not an astronomer (IANAA), but I would guess the discrepancy lies in the assumed values of deltaT, the difference between Dynamical Time and Universal Time. For a taste of the topic, see: http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&threadm=DWELLS.9 5Mar19183528%40fits.cv.nrao.edu&rnum=8&prev=/groups%3Fq%3Dusno%2Bdeltat%26hl %3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26selm%3DDWELLS.95Mar19183528%2540fi ts.cv.nrao.edu%26rnum%3D8 I recently changed the values of deltaT used by Pocket Stars (http://www.nomadelectronics.com) to more closely match USNO values: // julian deltaT 2451544.5000000, /*2000.0000,*/ 63.83, 2453371.5000000, /*2005.0000,*/ 66.00, 2455197.5000000, /*2010.0000,*/ 70.00, Using these values for deltaT, Novas, and DE405, the equinox as calculated by Pocket Stars was at 6:48:53. - Jay -----Original Message----- From: Navigation Mailing List [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM] On Behalf Of Fred Hebard Sent: Sunday, March 21, 2004 4:05 PM To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM Subject: Re: equinox Here are the Sun's declination as reported in the Nautical Almanac versus time. Looks pretty linear to me. The discrepancy may lie elsewhere, such as the system of coordinates. When I said the time was exactly 6:48:00, I meant the calculation indicated 6:48:00, not 6:48:01 or 6:47:59. As both you and I said, it would be nice if an experienced astronomer would chime in here. Fred