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