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Re: tropical degrees for Magellanic Clouds

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  • mahtezcatpoc
    ... at the ... projected ... Yeah. ... (because he ... the sky ... see the ... Okay. ... Meaning that if you were to use ranges, just about everybody would
    Message 1 of 2 , Dec 31, 2005
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      --- In thefixedstars@yahoogroups.com, "Diana K. Rosenberg"
      <ye-stars@i...> wrote:
      >
      > Date: Thu, 29 Dec 2005 23:08:13 -0800 (PST)
      > From: Mark Andrew Holmes <mahtezcatpoc@y...>
      > Subject: The Magellanic Clouds
      >
      > Mark wrote:
      >
      > If anybody can give us Tropical longitude ranges for
      > Nubecula Major (the Large Magellanic Cloud) and
      > Nubecula Minor (the Small Magellanic Cloud) since
      > 1900, I would appreciate it. Vivian Robson has them at
      > 4 Gemini to 0 Cancer and 15 Aries to 4 Taurus,
      > respectively. I'm sure that's changed since he
      > published *The Fixed Stars and Constellations in
      > Astrology.* Robson doesn't give minute values, either,
      > just the degrees.
      >
      > Hi Mark,
      >
      > I do not have anything "official" - but using the illustrations
      > in Staal's The New Patterns in the Sky (pp 243-245), I would
      > say that the Large Magellanic Cloud (in Dorado/Mensa) runs
      > from approx RA 4.6 to 6.5, and from about Declination -65 to -73,
      > and the Small Magellanic Cloud (in Tucana) from approx
      > RA 0.4 - 1.4, Declination -72 to -77.
      >
      > Converting these figures to tropical degrees, epoch 2000, I ran into
      > trouble with the Larger Cloud, because it is in Dorado/Mensa, right
      at the
      > South Pole of the Ecliptic! Lines of Celestial Longitude (i.e. tropical
      > degrees) all run together at that point; so even a small difference in
      > (Equatorial) RA and Declination becomes a HUGE difference when
      projected
      > up on to the Ecliptic.


      Yeah.


      >
      > I used Bernadette's Starlight Program and used Lincoln's chart
      (because he
      > had stuff in Aquarius and Aries), then set it to zoom out so that
      the sky
      > could be viewed as a globe, and set it to show (in the southern sky)
      > both the lines of Right Ascension (Equator-based) and lines of celestial
      > longitude (Ecliptic based).
      >
      > That's when I saw the problem (it looks like 2 rival spider webs
      > interfering with each other!).
      >
      > If you want, I can scan it and send it as an attachment so you can
      see the
      > problem.




      Okay.




      >
      > Using Mark Pottenger's conversion program (Mark has a
      > degree in astronomy) here are the results for the LMC:
      >
      > RA 4.6 at Dec 73 South: 8 Aquarius 53
      > RA 6.1 at Dec 73 South: 26 Sagittarius 06
      > RA 4.6 at Dec 65 South: 0 Aries 34
      > RA 6.1 at Dec 65 South: 22 Cancer 12
      >
      > The Smaller Cloud, in Tucana (just north of Octans, the South
      > Pole of the EQUATOR), is easier:
      >
      > RA 0.4 at Dec 72 South: 11 Aquarius 24
      > RA 1.4 at Dec 72 South: 16 Aquarius 12
      > RA 0.4 at Dec 77 South: 1 Aquarius 26
      > RA 1.4 at Dec 77 South: 3 Aquarius 48
      >
      > So you see that the Smaller Cloud runs from (very approximately)
      > 1 to 16 Aquarius; but the Larger Cloud runs, in tropical terms,
      > from 26 Sag to 22 Cancer, a span of 206 degrees!

      Meaning that if you were to use ranges, just about everybody would
      have something on Nubecula Major.

      Okay.


      >
      > This is why it makes more sense to just work with the "center" of
      > these 2 clouds:
      >
      > In:
      >
      > http://www.daviddarling.info/encyclopedia/L/LMC.html
      > http://www.ebicom.net/~rsf1/fun/sm-cmts.htm:
      > The coordinates given for the Large Magellanic Cloud are:
      > Equatorial - RA 05 hrs 23.6 min, Dec -69 deg 45 min
      > Which gives: 12 Aquarius 33
      > But:
      > http://www.atnf.csiro.au/research/smc_h1/get_spectrum.html
      > has, for the 2 clouds: (centered at) 05 20, -68 44 and 01 01, -72 56
      > Which gives:
      > 25 Aquarius 42 for the LMC, 12 Aquarius 28 for the SMC
      > A headache, for sure. Lord only knows where Robson got his results.


      Okay, so if you can't get a definitive position for the center of the
      LMC (and anybody's "definitive position" might be controversial), then
      there's not much point in using it at all, is there?

      Mark A. Holmes
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