I/201 XZ Catalog of Zodiacal Stars (XZ80N) (Dunham+ 1995)
XZ Catalog of Zodiacal Stars (Version XZ80N)
Dunham D.W., Warren W.H. Jr.
<(Unpublished) January 1995>
ADC_Keywords: Combined data ; Positional data; Zodiacal regions
Description:
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 (a region hereafter
called "the Zodiac"), 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
succeeding 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.
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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
b1950.dat 125 32221 XZ80N catalog with B1950.0 positions
j2000.dat 125 32221 XZ80N catalog with J2000.0 positions
xz80n.txt 78 389 *The original document
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Note on xz80n.txt:
Most of the information in the original document is in ReadMe.
However, xz80n.txt contains two Fortran programs for converting
the sexagesimal form of the positions to the form of seconds from the
origin, which are not included here.
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See also:
I/61 : AGK3 Catalogue (Dieckvoss, Heckmann 1975)
I/131 : SAO Star Catalog J2000 (SAO Staff 1966; USNO, ADC 1990)
Byte-by-byte Description of file: b1950.dat, j2000.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [X]
2- 6 I5 --- XZ [1,32221]+ Sequential number
7- 16 A10 --- DM Durchmusterung identifier (BD, SD, CD)
17 A1 --- m_DM *Multiplicity code
18- 21 F4.1 mag Vmag 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/yr 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 10mas/yr pmDE Proper motion in Dec (arcsec/century)
56- 59 F4.3 arcsec plx ?Trigonometric parallax
60- 63 I4 km/s RV ?Radial velocity
64- 65 I2 --- c2C *Second catalog code (*)
66- 70 I5 --- c2ID Second catalog number
71- 76 I6 --- SAO *?SAO Catalog number
77- 79 A3 --- SpType Spectral type
80- 83 F4.2 arcsec e_RAs Error in RA (at epoch)
84- 87 F4.2 10mas/yr e_pmRA Error in RA proper motion
88- 91 F4.2 arcsec e_DE Error in Dec (at epoch)
92- 95 F4.2 10mas/yr e_pmDE Error in Dec PM (at epoch)
96- 98 I3 yr Ep-1850 *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 --- src *Source catalog code
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Note on m_DM:
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, DEm, DEs:
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 c2C: the code is the following:
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 is 80 and
the SAO number is within the range of 1 to 16, the SAO number is
actually an AGK3 error code.
Note on Ep-1850:
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 src: source catalog codes are:
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 (see Cat. I/143)
92 = FK4 Supplement/FK3 (see Cat. I/143)
93 = N30 (Cat. I/80)
96 = Pleiades catalog (Eichhorn, see Cat. I/90, I/163)
97 = ZZ87 (Harrington and Douglass)
98 = Perth 70 (Cat. I/62)
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.
The other catalogs are:
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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
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Different variations on the XZ catalog format have been used for
internal use at the U.S. Naval Observatory and for the other catalogs.
They are described below for the different logical record lengths
involved:
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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.
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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:
A double precision function Fortran routine SECNDS is mentioned above;
it converts a packed number in sexagesimal 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 sexagesimal form.
These subroutines are included in the "z80n.txt" file.
History:
* Changes to the catalog as received (Nancy G. Roman, 28-Feb-1995):
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.
(End) N. G. Roman [NASA/NSSDC/ADC] 28-Feb-1995