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I/201 XZ Catalog of Zodiacal Stars (Dunham & Warren 1995)
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XZ Catalog of Zodiacal Stars
Dunham D.W., Warren W.H. Jr.
<unpublished 1995 January>
===============================================================================
ADC_Keywords: Astrometric data; Combined data; Positional data;
Zodiacal regions
Abstract:
The XZ catalog was created at the U. S. Naval Observatory in 1977 by Richard
Schmidt and Tom Van Flandern, primarily for the purpose of generating
predictions of lunar occultations, and for analyzing timings of these events.
It was designed to include all stars from Robertson's Zodiacal Catalog (ZC),
the SAO catalog, and the AGK3 catalog that are within 6d 40' of the ecliptic,
which is as far as the Moon's limb can ever get as seen from anywhere on the
Earth's surface, leaving some margin for stellar proper motions and change in
the obliquity of the ecliptic over the course of three centuries. The
original version contained 32,221 entries. Since that time, a number of
changes have been made in suceeding versions, including better positions and
proper motions, and the elimination and addition of stars. The catalog
contains visual magnitudes and radial velocities as well as astrometric data.
History:
The XZ catalog was created at the U. S. Naval Observatory in 1977 by Richard
Schmidt and Tom Van Flandern, primarily for the purpose of generating
predictions of lunar occultations, and for analyzing timings of these events.
It was designed to include all stars from Robertson's Zodiacal Catalog (ZC),
the SAO catalog, and the AGK3 catalog that are within 6d 40' of the ecliptic,
which is as far as the Moon's limb can ever get as seen from anywhere on the
Earth's surface, leaving some margin for stellar proper motions and change in
the obliquity of the ecliptic over the course of three centuries. Hereafter,
this region will be called "the Zodiac". The catalog contains 32,221 entries.
Two years after the catalog was created, and observations were already
reported using its numbers, it was found that about 200 stars near the
equator from the AGK3 catalog were outside the Zodiac, and a similar number
that should have been included were not. Since the numbering system had
already been established, the catalog was not changed to correct this
deficiency. Over the years, some errors in the catalog, due mainly to errors
in the SAO and AGK3, were corrected. A few stars with very bad data were
"eliminated" by changing their declination to -89d and adding 40 to their
magnitudes. In 1986, most of the stellar positional data were replaced with
improved data from Harrington's and Douglass' Zodical Zone (ZZ) catalog,
which used for its observing list SAO stars in the Zodiac (actually broader
than the XZ Zodiac because ecliptic latitudes to +/-15d were used) north of
declination approximately -25d. The positional data for many of the stars
south of declination -25d with right ascensions greater than 18h were
improved with data from the Lick Voyager Uranus catalog. In 1991, the
photographic magnitudes of the AGK3 stars not in the SAO were converted to
photovisual magnitudes by applying corrections based on each star's spectral
type, when available. Stellar magnitudes and double-star codes have been
updated periodically based on reports from observers. Each time a series of
updates was made, the XZ version was changed. The current version is XZ80N,
created during the summer of 1992. Late in the summer of 1992, Mitsuru Soma
in Japan created a J2000 version of the XZ, which we call XZ80NJ2. The next
update is planned for 1994, when the positional data may also be replaced
with PPM data; probably only the J2000 version will be updated. The XZ
catalog is no longer maintained at the U. S. Naval Observatory (USNO); it is
now maintained by the International Occultation Timing Association (IOTA).
The changes made to the different versions of the XZ catalog during the past
several years have been documented in Occultation Newsletter, IOTA's
quarterly publication.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
B1950.dat 125 32221 B1950.0 catalog
J2000.dat 125 32221 J2000.0 catalog
xz80n.doc 80 389 The original document
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Most of the information in the original document is in ReadMe. However, the
former does contain two Fortran programs for converting the sexigessimal form
of the positions to the form of seconds from the origin.
Byte-by-byte Description of file: B1950.dat, J2000.dat
----------------------------------------------------------------------
Bytes Format Units Label Explanations
----------------------------------------------------------------------
1 A1 --- X [X]
2- 6 I5 --- num +Sequential number
7- 8 A2 --- dmID Durchmusterung identifier
9 A1 --- dmsign Sign of DM zone
10- 11 I2 --- dmzone ?Durchmusterung zone
12- 16 I5 --- dmnum ?Durchmusterung number
17 A1 --- dscode *Double-star code
18- 21 F4.1 mag m(v) !Visual magnitude
22- 23 I2 h RAh *!Right ascension (B1950.0)
24- 25 I2 min RAm !Right ascension (B1950.0)
26- 31 F6.3 s RAs !Right ascension (B1950.0)
32- 38 F7.3 0.01s/a pmRA !Proper motion in RA
39 A1 --- De- Sign of declination
40- 41 I2 deg DEd *!Declination (eq & ep B1950.0)
42- 43 I2 arcmin DEm !Declination (eq & ep B1950.0)
44- 48 F5.2 arcsec DEs !Declination (eq & ep B1950.0)
49- 55 F7.2 0.01arcsec/a cpmDE !Proper motion in Dec
56- 59 F4.3 arcsec pi ?Trigonometric parallax
60- 63 I4 km/s RV ?Radial velocity
64- 65 I2 --- cat2cd *!Second catalog code (*)
66- 70 I5 --- cat2num !Second catalog number
71- 76 I6 --- SAO *?SAO Catalog number
77- 79 A3 --- sp Spectral type
80- 83 F4.2 s eRA !Error in RA (at epoch)
84- 87 F4.2 s/a epmRA !Error in RA PM (at epoch)
88- 91 F4.2 arcsec eDE !Error in Dec (at epoch)
92- 95 F4.2 arcsec epmDE !Error in Dec PM (at epoch)
96- 98 I3 yr epoch *!Epoch - 1850 (integer years)
99-120 A22 --- name *Star name or catalog designation
121-122 A2 --- code *Special coding
123 I1 --- encode !Encoding for bytes 116-120
124-125 I2 --- source *!Source catalog code
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Note on dscode:
Listed below are the double-star codes currently in use. For "triple,"
three stars are usually meant, but there may be other known stars in the
system.
A - Listed by Aitken and/or Burnham (ADS, BDS)
B - Close double with third star nearby with separate XZ number
C - Listed by Innes, Couteau, or other visual observers
D - Primary of double; secondary has separate XZ entry
E - Secondary of double; primary has separate XZ entry
F - Following component
G - A or C with second star either M, J, U, or V and third star referred
to second star
H - Triple: J, U or V and M
I - O with secondary either J, U, or V (third star's data referred to
secondary)
J - Single-lined spectroscopic binary; separation probably <0.01"
K - U or V, but duplicity doubtful ("possible" double)
L - Triple: J or U, and V; or all V; or all J
M - Mean position of close pair
N - North component
O - Orbital elements available
P - Preceding component
Q - Triple: J or U or V, and O
R - Triple: O and O
S - South component
T - Triple: V and A or C; or all A and/or C
U - Separation <0.01" (usually 2-line spectroscopic binary)
V - Separation >0.01", but not visual (occultation, interferometric, or
speckle component)
W - Triple: J or U, and A or C
X - Probably a close double, not certain
Y - Triple: K or X, and A or C
Z - Triple: O and A or C or V or X or L
$ - M with secondary either M, J, U, or V (third star's data referred to
secondary star)
Note on RAh, RAm, and RAs:
The epoch and equinox of the Right Ascension and Declination have been
B1950 for most of the history of the XZ. In 1992, Mitsuru Soma at the
National Observatory in Mitaka, Japan, made a J2000 version of XZ80N,
where the epoch and equinox of the R.A. and Dec. were converted to J2000
from B1950 using the Astronomisches Rechen-Institut's procedure for this
conversion.
Note on DEd:
The declinations can be read into one double-precision variable with an
F9.2 format, rather than with a format such as given (separate variables
for d,',""), although the sign is always in byte 39. Save the original
read-in value (so it can be tested at the end for the sign), then take
its absolute value for decoding into degrees, minutes, and seconds of
arc. A subroutine like the Fortran function SECNDS can be used convert
the full number into seconds of arc counted from the equator; it can
similarly be used to convert the right ascensions into seconds of time,
0 - 86400, counted from the equinox, by reading the R.A. as one
double-precision number with an F9.3 format rather than with the format
indicated.
Note on cat2cd:
80 AGK3 (not ZC, not SZ; the second catalog code number in this
case is the number of the star in the AGK3 zone, which can be
determined from the degrees of declination for the J2000 version of
the catalog; for these stars, the AGK3 zone and number are also
given in the name fields)
90 ZC (Robertson ZC)
94 SZ (SAO, not ZC; the SZ was a Zodical subset of the SAO catalog, a
predecessor of the XZ that was replaced by the XZ)
Note on SAO:
Some stars are not in the SAO catalog, mainly stars whose data were
obtained from the AGK3. In the Zodiac, the SAO numbers are always
greater than 50,000. So the SAO field was used for the AGK3
error code, which ranges from 1 to 16. If the second catalog code is80
and the SAO number is within the range of 1 to 16, the SAO number is
actually an AGK3 error code.
Note on epoch:
This is the mean epoch of the observations that should be used only for
calculating the error in the star's position at a specified time when
using the errors in bytes 80-95.
Note on source:
Source catalog codes
10-60 XZ/SAO
69 XZ/GC
70 SAO/GC (very poor data)
76 XZ/GC
80 AGK3/XZ
81 ZC/Perth 70 (combined ZC and P70 data)
82 Yale
84 Lick Voyager catalogs (usually combined with SAO data)
90 ZC/XZ
91 FK4
92 FK4 Supplement/FK3
93 N30
96 Pleiades catalog (Eichhorn)
97 ZZ87 (Harrington and Douglass)
98 Perth 70
Note on name, code:
The star names sometimes extend into the coding field when there
is no code present. The codes give information on source
catalogs and their numbers. Bytes 99-122 can just as well be
read as a single field with A24. Bytes 121-122 contain a code
if byte location 120 is blank; if byte location 120 is not
blank, then bytes 121-122 contain the end of the star name. If
one wants only the star names and not the code, byte location
120 must be tested for blank; if it is blank, then bytes 121-122
should be replaced with two blank bytes.
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Other USNO lunar occultation catalogs:
David Dunham created other star catalogs for special occultation
predictions at USNO; these have a format similar to that of the XZ, where the
character in byte location 1 identified the catalog, when field 1 was
included. In 1977, the K-catalog was created just before the XZ, to include
AGK3 and southern Yale catalog stars (a few hundred, some as bright as 7th
mag., were not in the SAO catalog, and therefore not in the SZ, since no
proper motions were given for them) that were not in the SZ catalog being
used at the time. It included more than 7000 stars to supplement the SZ. In
1978, after the XZ was established and used for occultation predictions, the
K-catalog was modified so that it would exactly supplement the XZ, but
without changing the sequence, since predictions had already been distributed
and observations reported using K-catalog numbers in 1977. Most (but not all)
of the AGK3 stars in the K-catalog are also in the XZ, so these were
"removed" (at least for lunar occultation prediction purposes) by changing
the degrees of declination of these stars in the K-catalog to -89. So
although there are still more than 7000 entries in the K-catalog, only
several hundred of them are valid; other users may simply want to remove the
invalid entries by rejecting all stars with declinations less than -88d.
The other catalogs do not cover the whole Zodiac, but only certain fields of
special interest, such as galactic clusters and star fields that were
traversed by the Moon during total lunar eclipses. These catalogs include
stars down to 11th and 12th magnitude usually obtained from the Astrographic
Catalogs. They were cross-referenced with the XZ, and the data of matched
stars replaced with XZ data; the X or ZC number for such stars was given in
the DM field #2, which for these catalogs must be read with the format A3,I5,
since non-numeric data are sometimes included in all byte locations of the
"zone". The occultation prediction program at USNO required stars to be
located at every hour of right ascension. Therefore, "spacer" entries were
needed for these catalogs to fill this requirement. The magnitudes of these
false-star entries were given as either 40 or 50 and the declinations as
either -89d or -90d.
Be careful when using the declinations from these other catalogs, since,
unlike the XZ, the sign of the declination is not always in byte location 37.
The declinations should be read with an F9.2 format, since the minus for
negative declinations is not always in byte locations 37 or 38. Save the
original read-in value (so it can be tested at the end for the sign), then
take its absolute value for decoding into degrees, minutes, and seconds of
arc. A subroutine like the Fortran function SECNDS can be used convert the
full number into seconds of arc counted from the equator; see the appendix
below.
The other catalogs are listed below.
Logical Physical Occultation
Cat. Record Record Newslet. Ref.
Name Length Length Vol./No./pages Brief description
------------------------------------------------------------------------------
5BM 80 8000 1/4/29-31 For 1975 May lunar eclipse
2/4/37 M, mainly for 1979 eclipses
3/1/3 B, for 1981 eclipses
"5BM" is an RA-sorted combination
of the above 3 catalogs
E 86 8600 3/12/249 & For eclipses in 1985 and 1986
3/16/345
J 104 10400 1/13/138-139 Hyades, Milky Way, 1977 eclipses,
& 1/14/145-147 other clusters
& 1/16/170
C 104 10400 2/14/188-189 Milky Way, 1982 eclipses, clusters
& 2/16/222-224
K 86 8600 1/13/138-139 See above
L 86 8600 4/11/263-266 1989-90 eclipses, Lick-Voyager cats.
& 4/12/301
& 4/14/336
The above describes the format of the 123-byte records in the normal export
version of the XZ catalog. However, different variations on this format have
been used for internal use at the U. S. Naval Observatory and for the other
catalogs. They are descibed below for the different logical record lengths
involved.
Record
Length Description
------------------------------------------------------------------------------
80 Includes fields 2-19 described above, that is, byte locations
7 - 96.
86 Includes fields 1-19 described above, that is, byte locations
1 - 96. The first byte location contains the single-letter
USNO catalog code identifier (E, K, etc.).
104 Includes fields 2-21 described above, that is, byte locations
7 - 119. The C and J catalogs use this format, and some of
the records at the end of the catalog (at least for C) are
blank. For the C and J catalogs, the name fields (20 and 21)
are all blank.
Since the 80- and 104-byte versions do not include field 1 (XZ number), the
sequential number must be obtained by counting entries (logical records) from
the beginning, first entry = X00001, second = X00002, etc. (or first =
C00001, second = C00002, etc. for the C-catalog, etc.).
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Additional Information:
If additional information about the XZ catalog is needed, contact Dr. David
W. Dunham, IOTA, 7006 Megan Lane, Greenbelt, MD 20770-3012, Telephone:
301-953-5609; E-mail: dunham@nssdca.gsfc.nasa.gov
A double precision function Fortran routine SECNDS is mentioned above; it
converts a packed number in sexigessimal form, HHMMSS.SSS for R.A.'s and
+/-DDMMSS.SS for declination, into a pure count of seconds from the origin.
Another double precision function, SEX, does the inverse transformation from
pure seconds to the packed sexigessimal form. These subroutines are listed
below.
Double Precision Function Secnds (A)
C Convert D,M,S or H,M,S into seconds
Double Precision A,B,C
J = IDINT (1.D-4 * (A + DSIGN (1.D-4,A)))
L = IDINT (A + DSIGN (1.D-4,A))
K = L - 10000 * J
M = 40 * (90*J-K/100) + K
B = M
C = L
Secnds = B + A - C
Return
End
Double Precision Function Sex(X)
C Convert number in seconds to sexigessimal form
C X is in seconds. This function is the inverse of Secnds
Implicit Real*8(A-H,O-Z)
Data Ist/0/
If (Ist .gt. 0) Go to 10
Ist = 1
G = 1.D0 / 60.D0
H = G * G
10 A = DABS(X)
B = A * H
I = IDINT(B)
C = I
C C is integer degrees or hours
A = A - 3600.D0 * C
B = A * G
I = IDINT(B)
D = I
C D is integer minutes
A = A-60.D0 * D
Sex = 10000.D0 * C + 100.D0 * D + A
If (X .lt. 0.D0) Sex = -Sex
Return
End
Changes to the catalog as received:
This catalog and accompanying documentation were received from David
Dunham in excellent shape. However, no decimal points were included
(i.e., the decimal points were implicit.) As our current program to
check catalogs does not handle implicit decimal points, the undersigned
changed the formats to integer formats for checking. It was decided that
these were unsuitable for general use, so the decimal points were
inserted and the formats changed back to F formats. The zeros were
omitted in the parallax, radial velocity, and SAO fields if no data were
entered (i.e., the fields are blank). Wayne Warren subsequently moved
the signs in the proper-motion and radial-velocity fields so that they
always occur in the leftmost byte. He also added prefixes (BD, SD, CD)
to the DM identifiers because both SD and CD stars occur in zone
-22 degrees.
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(End) N. G. Roman [NASA/NSSDC/ADC] 28-Feb-1995