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    Re: TEN lunars stars?
    From: Herbert Prinz
    Date: 2003 Dec 17, 03:23 -0500

    Frank Reed wrote:
    
    > I was browsing the Nautical Almanac from 1778 yesterday, and I was
    > surprised to discover another lunar distance star. I was under the
    > impression that the nine standard ones were in place right from the
    > first edition. The extra star is Beta Capricorni. It's in a good
    > location for a lunars star, but rather faint. I suppose that's why it
    > doesn't appear in later editions. Were there any other "occasional"
    > lunars stars?
    
    I did no systematic research, but in the Connoissance des temps from
    1790 Beta Capricorni does not show. So I would assume that it was gone
    for good by then in the French and English ephemerides. Spot checks in
    the N.A. from 1804, 1819, 1911 and Connaissance from 1845 revealed no
    other stars than the usual nine.
    
    One cannot blame Maskelyne for trying alternatives to Altair, but why
    not Sigma Sag. (Nunki)? With an ecliptic longitude of 282 deg, it is as
    far from Antares as Beta Cap. is from Fomalhaut, but it is a whole
    magnitude brighter than Beta Cap.
    
    The pickings are slim in this part of the sky. In addition to the
    faintness of Beta Cap., there may also be the danger of confusing it
    with Alpha Cap., which is near by and of nearly the same magnitude.
    Alpha Aquilae (Altair), which is roughly at the same ecliptic longitude
    as Beta Cap., has its own problem: It is so far from the ecliptic that
    it becomes useless near conjunction with the Moon. The Nautical Almanac
    1819 stops tabulating Altair when the distance sinks under 60 deg. The
    French are bolder and go down to 50 deg. This leaves normally only a
    three day window on each side of the Moon during which the star can be
    used comfortably.
    
    Some relief came in 1823 when Schumacher started publishing the
    distances to the four navigational planets. Does anybody know the exact
    year when these distances were included in the French and English
    almanacs?
    
    
    Here is a list of the official distance stars:
    
    Name                Bayer          FK5 #         Lon   (apparent J2000)
    Lat           Mag.               RA   (astrometric)  Dec
    
    HAMAL      ALP  ARI     74     37?39'41"   N  9?57'58"   2.00     2h 07m
    10s    N 23?27'45"
    ALDEBARA   ALP  TAU    168     69?47'25"   S  5?28'03"   0.85     4h 35m
    55s    N 16?30'33"
    POLLUX     BET  GEM    295    113?13'03"   N  6?41'02"   1.14     7h 45m
    19s    N 28?01'34"
    REGULUS    ALP  LEO    380    149?49'45"   N  0?27'53"   1.35    10h 08m
    22s    N 11?58'02"
    SPICA      ALP  VIR    498    203?50'10"   S  2?03'15"   0.97    13h 25m
    12s    S 11?09'41"
    ANTARES    ALP  SCO    616    249?45'12"   S  4?34'11"   0.96    16h 29m
    24s    S 26?25'55"
    ALTAIR     ALP  AQL    745    301?45'59"   N 29?18'16"   0.77    19h 50m
    47s    N  8?52'06"
    FOMALHAU   ALP  PSA    867    333?51'10"   S 21?08'14"   1.16    22h 57m
    39s    S 29?37'20"
    MARKAB     ALP  PEG    871    353?28'48"   N 19?24'28"   2.49    23h 04m
    46s    N 15?12'19"
    
    
    And here another one with more stars brighter than 3.1 and situated
    within 5 degrees of the ecliptic:
    
    Name                Bayer          FK5 #         Lon   (apparent J2000)
    Lat           Mag.               RA   (astrometric)  Dec
    
    ALCYONE    ETA  TAU    139     59?59'35"   N  4?03'04"   2.87     3h 47m
    29s   N 24?06'18"
               ZET  TAU    211     84?47'11"   S  2?11'45"   3.00     5h 37m
    39s   N 21?08'33"
               MU   GEM    241     95?18'14"   S  0?49'13"   2.88     6h 22m
    58s   N 22?30'49"
               EPS  GEM    254     99?56'27"   N  2?04'12"   2.98     6h 43m
    56s   N 25?07'52"
    ZUBENELG   ALP2 LIB    548    225?04'32"   N  0?19'59"   2.75    14h 50m
    53s   S 16?02'30"
    DSCHUBBA   DEL  SCO    594    242?33'46"   S  1?59'09"   2.32    16h 00m
    20s   S 22?37'18"
    GRAFFIAS   BET1 SCO    597    243?10'54"   N  1?00'28"   2.62    16h 05m
    26s   S 19?48'20"
               SIG  SCO    607    247?47'27"   S  4?02'14"   2.89    16h 21m
    11s   S 25?35'34"
               LAM  SGR    692    276?18'27"   S  2?08'08"   2.81    18h 27m
    58s   S 25?25'18"
    NUNKI      SIG  SGR    706    282?22'32"   S  3?26'58"   2.02    18h 55m
    16s   S 26?17'48"
               PI   SGR    720    286?14'32"   N  1?26'13"   2.89    19h 09m
    46s   S 21?01'25"
               BET  CAP    762    304?02'18"   N  4?35'20"   3.08    20h 21m
    01s   S 14?46'53"
               DEL  CAP    819    323?32'04"   S  2?36'07"   2.87    21h 47m
    02s   S 16?07'38"
    
    Most of these are too close to a much brighter one from the first list
    to be of any practical value. Nunki is the exception.
    
    Herbert Prinz
    
    
    

       
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