II/271A TASS Mark IV patches photometric catalog, version 2 (Droege+, 2007)
TASS Mark IV Photometric Survey of the Northern Sky
Droege, T. F., Richmond, M. W., Sallman, M.
<Publ. Astron. Soc. Pac. 118, 1666 (2006)>
=2006PASP..118.1666D 2006PASP..118.1666D
=2007PASP..119.1083R 2007PASP..119.1083R (Addendum)
ADC_Keywords: Surveys ; Photometry ; Stars, variable
Keywords: stars: general -- surveys
Abstract:
The Amateur Sky Survey (TASS) is a loose confederation of amateur and
professional astronomers. We describe the design and construction of
our Mark IV systems, a set of wide-field telescopes with CCD cameras
which take simultaneous images in the V and I passbands. We explain
our observational procedures and the pipeline which processes and
reduces the images into lists of stellar positions and magnitudes.
We have compiled a large database of measurements for stars in the
northern celestial hemisphere with V-band magnitudes in the range
7<V<13. This paper describes data taken over the four-year period
starting November, 2001. One of our results is a catalog of repeated
measurements on the Johnson-Cousins system for over 4.3 million stars.
This Version 2 of the catalog corrects a systematic error in
photometry as function of Declination.
Description:
The Mark IV patches catalog contains summary information for sources
detected simultaneously in V and I passbands on at least 5 occasions.
The magnitudes in the table are the interquartile mean of all
measurements, some of which may have been taken under poor conditions.
In addition to the ordinary standard deviation from this mean, the
table includes statistics based on ensemble analysis of stars within
small patches one degree on a side; this removes some of the
systematic errors in photometry and provides a more accurate estimate
of intrinsic stellar variability.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
patch2.dat 112 4353670 *Properties of objects detected repeatedly
during the Mark IV survey of northern sky (V.2)
v1/* . 29 Version 1 of the catalog
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Note on patch2.dat: the full file is split in 24 parts, patch2.dat.00
to patches.dat.23, each corresponding to 1 hour in right ascension.
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See also:
II/230 : TASS Mark III photometric survey (Richmond+, 2000)
http://www.tass-survey.org : TASS Home Page
Byte-by-byte Description of file: patch2.dat
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Bytes Format Units Label Explanations
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1- 8 I8 --- TASS4 Index in Mark IV engineering database
10- 13 I4 --- o_TASS4 Number of good (V,I) measurement pairs
15- 23 F9.5 deg RAdeg Mean Right Ascension (J2000.0)
25- 31 F7.5 deg e_RAdeg Standard deviation from mean RA position
33- 41 F9.5 deg DEdeg Mean Declination (J2000.0)
43- 49 F7.5 deg e_DEdeg Standard deviation from mean Dec position
51- 56 F6.3 mag Vmag Interquartile mean of all V-band measurements (5)
58- 62 F5.3 mag e_Vmag Standard deviation from interquartile mean V
64- 68 F5.3 mag eVmag Standard deviation from mean V value in
ensemble analysis of local patch (1)
70- 75 F6.3 mag Imag Interquartile mean of all I-band measurements (5)
77- 81 F5.3 mag e_Imag Standard deviation from interquartile mean I
83- 87 F5.3 mag eImag Standard deviation from mean I value in
ensemble analysis of local patch (1)
89- 94 F6.2 --- dVmag Normalized measure of deviation from mean V
magnitude in ensemble analysis (2)
96-101 F6.2 --- dImag Normalized measure of deviation from mean I
magnitude in ensemble analysis (2)
103-109 F7.2 --- WS Welch-Stetson variability index (3)
111-112 I2 --- Proxy Proximity code (4)
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Note (1): Ensemble analysis of stars within a one-degree square patch of
sky yields a mean magnitude (with arbitrary zero point) for each star
and the standard deviation around that mean. Some measurements may be
discarded.
Note (2): In each patch, the typical scatter away from mean magnitudes is
estimated using all stars. The "Normalized measure of deviation" value
is computed by dividing an individual star's standard deviation from
its mean by this typical scatter.
Note (3): A normalized measure of the degree of correlation of V-band and
I-band variations from their mean values. See Welch and Stetson
(1993AJ....105.1813W 1993AJ....105.1813W) for a full description. The variability index
will be close to zero for stars with random variations which are
independent in each passband, or stars which vary by less than the
uncertainty of each measurement. It will be a large (greater than 2
or 3) positive value for stars which really do change significantly
in brightness.
Note (4): Bitwise combination of flags indicating neighbors which may be
close enough to contaminate measurements.
Flag F4 is set to 1 if at least one brighter star within 30 arcsec.
Flag F3 is set to 1 if at least one fainter star within 30 arcsec.
Flag F2 is set to 1 if at least one brighter star within 60 arcsec.
Flag F1 is set to 1 if at least one fainter star within 60 arcsec.
Proximity code is the sum 8*(F4) + 4*(F3) + 2*(F2) + 1*(F1)
Note (5): Original version of catalog contained systematic errors
depending on Dec position of star, due to a flatfielding effect.
The amplitude of the errors ranged from ±0.02mag to ±0.10mag,
worse near northern and southern edges of survey. The errors have
been modeled and removed for Version 2 of this catalog.
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Acknowledgements:
Michael Richmond, richmond(at)stupendous.cis.rit.edu
History:
* 18-Sep-2006: Version 1 of the catalog ("v1" subdirectory)
* 28-Jul-2007: Version 2 at CDS (Catalog II/271A)
(End) Michael Richmond [RIT, USA], Francois Ochsenbein [CDS] 30-May-2007