From d35bade38c2628c0fa73671c35ccad090b003dc5 Mon Sep 17 00:00:00 2001 From: Jean Connelly Date: Thu, 25 Jul 2024 12:03:16 -0400 Subject: [PATCH 1/2] Add a link to the old readme from the index --- docs/catalog-description-1p7.rst | 777 +++++++++++++++++++++++++++++++ docs/index.rst | 12 +- 2 files changed, 786 insertions(+), 3 deletions(-) create mode 100644 docs/catalog-description-1p7.rst diff --git a/docs/catalog-description-1p7.rst b/docs/catalog-description-1p7.rst new file mode 100644 index 00000000..94e4986c --- /dev/null +++ b/docs/catalog-description-1p7.rst @@ -0,0 +1,777 @@ +================================================ +THE AXAF Guide and Acquisition Star Catalog V1.7 +================================================ + +An all-sky astrometric and photometric catalog +prepared for the operation of Chandra +(formerly AXAF). version 1.7 September 2018 + +Introduction +============ + +The AXAF Guide and Acquisition Star Catalog (AGASC) is presented in +this set of FITS (Flexible Image Transport System) files, and may +be distributed in a variety of formats, including DAT (DDS format) +or CD-ROM (compact disc, read only memory in ISO 9660 format). This +issue, Version 1.7, corresponds to the AGASC as completed +18 September 2018. + +The primary source of data for the AGASC is the Guide Star Catalog +(GSC) for the Hubble Space Telescope (HST), version 1.1. The release +number of AGASC will remain at 1 unless a different base catalog is +incorporated to reach to fainter magnitudes. Historically, the +second catalog to be merged into AGASC1.1 was the Positions and Proper +Motions (PPM) Catalog. The latter provides magnitudes, stellar types, +and proper motions for stars brighter than about V=12, but is far from +complete across the sky. The third catalog merged into AGASC1.3 is +the Tycho Output Catalog (Tycho-1) from the Tycho star mapper on the +Hipparcos satellite. Tycho-1 provided high precisions astrometric and +photometric data for 1,058,332 stars, nearly complete +to V=10.5. The fourth catalog was the ACT Reference Catalog. This +subset of 988,758 TYC stars contained updated star positions and proper +motions for the epoch and equinox J2000.0, covering the entire sky. +The proper motions are from new reductions of the Astrographic +Catalogue combined with the positions in the Tycho Catalogue. +The 5th catalog merged in AGASC was the Tycho-2 catalog, with 2.5 +million stars 90% complete to V=11.5mag, and including proper motions +from ACT and various other catalogs. The major improvements +incorporated into AGASC1.5 include the following: + +1. Repair of GSC1.1 star ID rollover problem in regions 3588, 5706, and 7899. +2. Merge of Tycho-2 position, mag, and color data for 2.5 million stars. +3. Recalibration of the estimated ACA magnitudes (MAG_ACA) + and their errors (MAG_ACA_ERR) based on 1939 stars observed by the + Chandra Aspect Camera Assembly (ACA) between 1999-Sep to 2000-Oct. +4. Update of remaining GSC1.1 positions by positions from + the GSC-ACT catalog, reducing the systematic astrometric errors of + faint GSC1.1 stars by about a factor of two. +5. Update of spoiler codes provides a more sophisticated + measure of the effect of nearby stars on the best-fit centroid of a + guide star. +6. Update of CLASS code to denote galaxies identified + from pre-release J<12.5 2MASS galaxy catalog. + +Version 1.6 was the third on orbit calibration of the AGASC. Using more +than 30000 aspect camera star observations from over the course of the +Chandra mission we were able to calculate the ACA response to a much +higher precision and over a broader band of star colors than previous +calibrations. AGASC 1.5 was deemed to require improvement for Chandra +flight operations after the discovery of a offset of up to 0.5 mags +between the predicted AGASC magnitude and the observed ACA magnitude +for red stars with a Tycho-2 color greater than 0.9. + +Version 1.7 improves upon the 1.6 calibration (observed ACA magnitude +and its error) for red stars by including the i magnitude information +from the AAVSO (American Association of Variable Star Observers) +Photometric All-Sky Survey (APASS) DR9. + +Organization of the FITS Data Files +=================================== + +The top directory includes the files:: + + ---------------------------------------------------------------- + readme.txt - Introduction. ASCII + agasc - Directory for AGASC FITS region files. + tables - Directory for AGASC supporting tables. + ---------------------------------------------------------------- + +In the tables subdirectory are these tables:: + + ---------------------------------------------------- + comments.txt - Introduction and general comments. ASCII + regions - Boundaries of GSC regions. FITS binary table + lg_reg_x - Index to large regions. FITS binary table + sm_reg_x - Index to small regions. FITS binary table + neighbors - Index of regions whose boundaries are within 1deg or + of the boundaries of each small region. ASCII + boundaryfile - Index of RA and DEC limits for each small region, in + decimal degrees. ASCII + offset_lookup.fits + - FITS binary lookup table of the predicted ACA centroid + offsets (in arcsec) caused by a star of brightness + difference dm, and radial positional separation dr. + outfilemap - full path beginning with large region for each + small region. ASCII + ---------------------------------------------------- + +As a result of merging of the GSC1.1 with the PPM and with the TYC, +and for expected merges with other catalogs in the future, we have +extended the AGASC format to include new information and references. +Published data include position, proper motion, epoch, parallax, a +magnitude, up to 2 colors, multiplicity and variability flags, and +source catalog IDs. Cross-references are included separately for 1) +position 2) mag 3) color 4) proper motion (p.m.), 5) parallax, and 6) +variability. Derived data include MAG_ACA, MAG_ACA_ERR, a high +p.m. flag ASPQ2, and spoiler star codes ASPQ1, and ASPQQ1-6, which +potentially relieve the Star Selection Algorithm (SSA) of such +computations. + +The AGASC stars are grouped with regions tables, as in the original +HST GSC. The AGASC consists of about 9537 regions tables containing +about 2,000 objects each. These will remain in FITS BINTABLE format, +with the directory structure described in FITS TABLE format. Stars +from constituent catalogs that were not matched to the original GSC1.1 +are included within the appropriate regions table based on region +boundaries in RA and DEC. Cross-references to the original star ID +numbers XREF_IDx are included from the original x=1-6 catalogs we +have matched. + + +Summary of the AGASC1.7 Format +============================== + +Each FITS regions table in the AGASC1.7 consists of 3 parts, the +primary header, the table header, and the table data. The conventions +for FITS Binary Tables are detailed in Cotton, Tody and Pence (1995, +A&A, 113, 159), or at http://fits.nrao.edu/FITS.html + +The length of the header information is the same for all the AGASC +regions tables. That length is 5x2880= 14400bytes. After these 14400 +bytes comes star data records. + +The data for each star amounts to 122 bytes, in 47 data columns for +AGASC1.7. Default values are -9999 or 0 where no data are available. +Many columns require data; these have no default values. Another +exception is COLOR1, whose default value is 0.7000 for most stars, +or 1.5000 for stars with COLOR1 greater than 1.5000. Details on all +columns and their defaults below. + +The FITS format data types and byte-lengths (8 bits to a byte) used +for each data item for each star are as follows:: + + fmt bytes fields tot type range + --------------------------------------------------------------- + A 1 0 0 character -128 - 127 + B 1 8 8 unsigned integer 0 - 255 + I 2 25 50 short integer -32768 - 32767 + J 4 6 24 long integer -2147483648 - 2147483647 + E 4 6 24 float variable -9.22337e+18 - 9.22337e+18 + D 8 2 16 double variable -1.70141e+38 - 1.70141e+38 + ---------------------------------------------------------------- + 122 bytes per star + +Summary of the AGASC Version 1.7 Entries +---------------------------------------- + +Each of the FITS regions files in the AGASC1.7 will contain the +following fields for each entry:: + + BYTES NAME - brief description + + 4 AGASC_ID - a unique long integer used for identification. + Currently a binary-packing of the region number, Hubble GSC star + number, and Tycho Output Catalog identifier TYC3. + No default value (must have an entry). + + 8 RA - double variable expressing right ascension in decimal degrees. + No default value (must have an entry). + + 8 DEC - double variable expressing declination in decimal degrees. + No default value (must have an entry). + + 2 POS_ERR - short integer value of position uncertainty, in milli-arcsec. + Default value of -9999 indicates no error available, or POS_ERR>32767. + + 1 POS_CATID - unsigned integer identifying the source of the + ra, dec, and pos_err. Default value is 0. + 0 - no associated catalog + 1 - GSC1.1 + 2 - PPM + 3 - Tycho Output Catalog (Tycho-1) + 4 - ACT + 5 - Tycho-2 + 6 - GSC-ACT + + 4 EPOCH - float variable identifying the epoch of the ra and dec + measurements. Default value of -9999.0 + + 2 PM_RA - short integer variable expressing proper motion in ra in units of + milli-arcsec per year. Default value of -9999. + + 2 PM_DEC - short integer variable expressing proper motion in dec in units + of milli-arcsec per year. Default value of -9999. + + 1 PM_CATID - unsigned integer identifying the source of the + pm_ra and pm_dec. The codes are the same as listed for pos_catid. + Default value is 0. + + 2 PLX - short integer variable expressing parallax in units of + milli-arcsec. Default value of -9999. + + 2 PLX_ERR - short integer variable expressing parallax error + in units of milli-arcsec. Default value of -9999. + + 1 PLX_CATID - unsigned integer identifying the source of the + pm_ra and pm_dec. The codes are the same as listed for pos_catid. + Default value is 0. + + 4 MAG_ACA - float variable expressing the calculated magnitude in the AXAF + ACA bandpass in units of magnitude. There is no default value. + + 2 MAG_ACA_ERR - short integer expressing the uncertainty of mag_aca in + units of 0.01mag. There is no default value. + + 2 CLASS - short integer code identifying classification of entry. + Default value of 0. + 0 - star + 1 - galaxy + 2 - blend or member of incorrectly resolved blend. + 3 - non-star + 5 - potential artifact + 6 - known multiple system + 7 - close to galaxy or other extended object + >100 - bad star in AGASC supplement (only via agasc package query); + class = 100 + bad star source ID. + + Note that code 1 is used only for a few hand-entered errata in + or for galaxies with matches to preliminary 2MASS galaxy catalog. + GSC1.1 galaxies successfully processed by the STSci software have + a classification of 3 (non-stellar). + + 4 MAG - float variable expressing magnitude, in mags. Spectral + band for which magnitude is derived is summarized in entry MAG_BAND. + There is no default value. + + 2 MAG_ERR - short integer value of magnitude uncertainty, in + 0.01mag units. There is no default value. + + 2 MAG_BAND - short integer code which identifies the spectral band + for which the magnitude value is derived. + There is no default value. + + Mag alpha Emulsion + Filter + --- ----- ---------------- + 0 0.72 IIIaJ + GG395 + 1 -0.15 IIaD + W12 + 3 1.28 Tycho B + 4 0.106 Tycho V + 6 -0.10 IIaD + GG495 + 8 -0.71 103aE + Red Plexiglass + 10 0.78 yellow objective + IIaD + GG4 + 11 1.16 blue objective +103aO + 12 1.16 blue objective +103aO + 13 0.13 yellow objective + 103aG + GG + 14 0.78 yellow objective + 103aG + GG + 16 0.00 IIIaJ + GG495 + 18 0.72 IIIaJ + GG385 + 21 0.00 PPM V mag + 22 1.00 PPM B mag + + 1 MAG_CATID - unsigned integer identifying the source of the + mag, mag_err, and mag_band. Codes are as follows: + + 0 - no associated catalog + 1 - GSC1.1 + 2 - PPM + 3 - Tycho Output Catalog (Tycho-1) + 4 - ACT + 5 - Tycho-2 + 6 - GSC-ACT + 100 - Chandra ACA estimated magnitude (only via agasc package query) + + 4 COLOR1 - float variable expressing the cataloged or estimated B-V color, + used for mag_aca, in mag. If no colors are available, the default + value is 0.7000. If Tycho-2 data show colors redder than + (B-V)=1.5, then the default value is 1.5000. True cataloged + color values are stored in COLOR2. + + 2 COL0R1_ERR - short integer expressing the error in color1 in units of + 0.01 mag. Default value of -9999. + + 1 C1_CATID - unsigned integer identifying the source of color1 and + color1_err. The codes are the same as listed for pos_catid. + Default value is 0. + + 4 COLOR2 - float variable expressing a different color, in mag. + For Tycho catalogs, this is the Tycho BT-VT color. + Default value of -9999.0 + + 2 COLOR2_ERR - short integer expressing the error in color2, iun + units of 0.01mag. Default value of -9999. + + 1 C2_CATID - unsigned integer identifying the source of color2 and + color2_err. The codes are the same as listed for pos_catid. + Default value is 0. + + 4 RSV1 - APASS V - i magnitude (COLOR3). Default value of -9999. + + 2 RSV2 - APASS V magnitude. Default value of -9999. + + 1 RSV3 - unsigned integer indicating if the MAG_ACA and MAG_ACA_ERR + were updated compared to AGASC1.6 (1 == updated, 0 == not updated). + + 2 VAR - short integer code providing information on known or suspected + variable stars. Default value of -9999. + 1 - suspected variable, with a suspected amplitude variation < 2 mag + 2 - suspected variable, with a suspected amplitude variation > 2 mag + 3 - known variable, with an amplitude variation > 0.2 mag + 4 - known variable, with large amplitude ( > 2 mag), for which an + ephemeris was necessary + 5 - known variable, with an amplitude variation < 0.2 mag + + 1 VAR_CATID - unsigned integer code identifying the source of VAR + Default value of 0. + + 2 ASPQ1 - short integer spoiler code for aspect stars. + An estimate, in 50milliarcsec units, of the worst centroid + offset caused by any star within 80arcsec. The simulated PSF + centroid offsets in the ACA are from offset_lookup.fits, indexed + brightness difference dm, and radial positional separation dr. + Default value of 0. + + 2 ASPQ2 - short integer proper motion flag. + Default value of 0. + 0 - unknown proper motion, or proper motion <500 milli-arcsec/year + 1 - proper motion >= 500 milli-arcsec/year + + 2 ASPQ3 - short integer distance (for Tycho-2 stars only) to + nearest Tycho-2 star, giving distance (in units of + 100milli-arcsec) computed for the epoch 1991.25. The maximum + value recorded for Tycho-2 stars is 999. + Default value of 999. + + 2 ACQQ1 - short integer indicating magnitude difference between the + brightest star within 53.3" of this star, and this star, in units + of 0.01 mags. Default value of -9999. + + 2 ACQQ2 - short integer indicating magnitude difference between the + brightest star within 107" of this star, and this star, in units + of 0.01 mags. Default value of -9999. + + 2 ACQQ3 - short integer indicating magnitude difference between the + brightest star within 160.5" of this star, and this star, in units + of 0.01 mags. Default value of -9999. + + 2 ACQQ4 - short integer indicating magnitude difference between the + brightest star within 214" of this star, and this star, in units + of 0.01 mags. Default value of -9999. + + 2 ACQQ5 - short integer indicating magnitude difference between the + brightest star within 267.5" of this star, and this star, in units + of 0.01 mags. Default value of -9999. + + 2 ACQQ6 - short integer indicating magnitude difference between the + brightest star within 321" of this star, and this star, in units + of 0.01 mags. Default value of -9999. + + 4 XREF_ID1 - long integer which is the star number in the + AGASC Version 1.0 (= GSC1.1). This is not a unique identifier. + Default value of -9999. + + 4 XREF_ID2 - long integer which maps the entry to that in the PPM. + Default value of -9999. + + 4 XREF_ID3 - long integer which maps the entry to that in the Tycho Output + Catalog (TYC2). Default value of -9999. + + 4 XREF_ID4 - long integer which maps the entry to that in the Tycho Output + Catalog (TYC3). Default value of -9999. + + 4 XREF_ID5 - long integer which maps the entry to that in a future + catalog. Default value of -9999. + + 2 RSV4 - short integer reserved for future use. Default value of -9999. + + 2 RSV5 - short integer reserved for future use. Default value of -9999. + + 2 RSV6 - short integer reserved for future use. Default value of -9999. + +History of the AGASC Version 1.7 +================================ + +The primary objective of the Chandra Aspect Camera Assembly (ACA) is to +measure the image positions of selected target stars and fiducial +lights in its field of view (FOV). The Chandra on board computer uses +gyro attitude data and ACA image centroids for real-time pointing. +Post-facto aspect determination is required for observations over 100 +sec to compensate for the apparent motion of the X-ray image on the SI +focal plane. When a maneuver is completed, at least 2 acquisition +stars must be acquired before acquiring guide stars and fiducial +lights. Up to 8 images can be tracked, including the fid lights. The +ground provides expected positions in the ACA FOV for these objects, +using the AGASC. At least 5 stars brighter than m=10.2 in the ACA +instrumental mag (MAG_ACA) system should be provided from ground 95% of the +time, anywhere on the sky, for the predicted end of life (EOL) FOV of +1.79 square degrees. To predict the ACA mag in advance, colors for +each star are required. Proper motions (p.m.) are also advisable, +since high p.m. stars could move significantly over the extended +lifetime of the Chandra mission. Parallax data are also advisable, +since parallaxes are not random, and in many cases will exceed +position errors. Currently, the largest consistent published catalogs +providing colors and proper motions are the Positions and Proper +Motions (PPM) Catalog and the Tycho Output Catalog (TYC). + +In 1996, we merged the PPM with the HST GSC1.1 to form AGASC1.1. +The optimal tolerance for positional matching of stars between the +GSC1.1 and the PPM was first determined, incorporating +p.m. information, and including all morphological classes (not just +stellar). Studying a variety of celestial positions, including or +excluding non-stellar objects, we find an optimal positional matching +tolerance of r<=10arcsec. To that separation, 295871 stars (99.74%) +are matched. To verify positionally matched stars, especially in more +crowded regions, we compare magnitudes between the GSC1.1 and PPM. +These mags are most often measured in different passbands. For +simplicity, and greatest likelihood of compatibility with future +merged catalogs, we convert all magnitudes to the V band for +comparison using approximate B-V colors derived from the PPM spectral +types. A magnitude tolerance of 2mag was allowed in the matching. +The large tolerance results from a variety of factors including at least +a) poor GSC1.1 magnitudes for bright stars, due to a poor mag-diameter +relation, halos and/or diffraction spikes b) large color uncertainties +since the PPM SpTypes may be crude and include no luminosity class, c) +random mag errors in either catalog. To that tolerance, +295274 stars (99.54%) are matched. The differential histogram of +matched stars for all PPM stars with PPM visual mags turns over at +V=9, and is only a few hundred stars by V=12. + +The original conversion from V to MAG_ACA was determined by convolving +the ACA bandpass with the Bruzual-Persson-Gunn-Stryker stellar +spectrophotometric atlas. This is an extension of the Gunn-Stryker +optical atlas (Gunn, J. E. & Stryker, L. L., 1983 ApJS, 52, 121) where +the spectral data have been extended into both the UV and the +infrared. The IR data are from Strecker et al. (ApJ 41, 501, 1979) +and other unpublished sources. Since the bandpass information for all +filters is normalized, the zeropoint for each filter was established +by convolution of the bandpass with a mag=0 spectrum of type G0V +(BD+26 3780 in the BPGS atlas, normalized to $V=0$). V and MAG_ACA mags +are then derived for each spectral type (SpType), resulting in a +V-MAG_ACA as a function of (B-V) color. Newer calibrations +of ACA magnitude estimates for AGASC1.6 and AGASC1.7 are described below. + +In 1997, we merged the TYC with AGASC1.1 to form AGASC1.2 This merging +was performed using the TYC ID codes TYC1 and TYC2, which are +cross-references to the HST GSC1.1 region number, and star number, +respectively. Although all TYC stars appear to have GSC1.1 +cross-references, there are 2 cases where stars are added to the +catalog. First, where the TYC ID code TYC3 is greater than one, Tycho +has resolved into multiples an object previously unresolved in the +GSC1.1 Second, some TYC stars have no AGASC1.1 counterpart either from +the GSC1.1 or the PPM). Again, data are checked to see if their +errors are smaller than those of data already in AGASC1.1 before being +substituted into AGASC1.2 However, PPM proper motions are assumed to +be superior due to their much longer baseline. Positional data and +epoch are updated with the proper motion to Epoch 2000. TYC parallax +measurements are all included for completeness, even though most are +not significant. These will be used only for post-facto aspect +(image) reconstruction. TYC V mags converted to Johnson V are +preferred, and TYC B mags are incorporated only in a few cases. +Johnson (B-V), as calculated in the TYC, are used for COLOR1 whenever +possible, with (BT-VT) now stored (redundantly) as COLOR2. +Multiplicity and variability information are also included. + +Due to the short (less than 4 year) lifetime of the Hipparcos +mission, most of the proper motions included in the TYC are of low +significance. Tycho positions make it the most accurate catalog of +comparable size at its epoch of observation, but its proper motions +degrade it to a sub-standard reference catalog in less than about 10 +years. The proper motions of the Tycho stars were improved from about +30 mas/year to about 3 mas/year by combining TYC positions +with AC2000 positions, yielding an average baseline of more than 80 +years. The ACT proper motion information and updated positions +were incorporated into AGASC1.3. + +Actual ACA mags for stars of a wide range of spectral types were +accumulated during the first few months of the mission, and it +proved important to generate more accurate mags for the catalog from +the MAG and COLOR1 data. This recalibrated coefficients were derived +from a fit to observed Aspect Camera magnitudes for 271 stars observed +between 1999 Oct 03 - Nov 20, and AGASC1.3 was recalibrated to create +AGASC1.4. Observed ACA mags for 1939 stars observed by the +Chandra Aspect Camera Assembly (ACA) between 1999-Sep to 2000-Oct +have been extracted and a calibrating polynomial refit by comparison +to colors from Tycho-1. + +In AGASC1.6, MAG_ACA is derived from V and BT-VT (COLOR2) for all +stars with valid COLOR2 from Tycho-2. MAG_ACA and MAG_ACA_ERR are +unchanged from AGASC 1.5 for stars not meeting these criteria. A +seven node cubic spline was fit to the offset between the observed +magnitudes and V-Band magnitudes for 30238 ACA star observations. + +In AGASC1.7, MAG_ACA is derived from V and BT-VT (COLOR2) and V-i +(COLOR3) for all stars with valid COLOR2 from Tycho-2 and valid COLOR3 +from AAVSO (American Association of Variable Star Observers) Photometric +All-Sky Survey (APASS) DR9. MAG_ACA and MAG_ACA_ERR are unchanged from +AGASC1.6 for stars not meeting these criteria. + +In early 2002, we merged in data from the Tycho-2 catalog, and +Tycho-2 supplement-1, described further below. Tycho-2 data +supercedes data from all previously merged catalogs whenever it is +available. Tycho-2 stars are matched to AGASC stars by the GSC star +ID, so that the final organization retains the original GSC star ID +and regions structure. + +The average stellar surface density of unspoiled stars brighter than +MAG_ACA=10.2 with color information ((ASPQ1=0, CLASS=0, C1_CATID.ne.0) +is 9.5 stars per square degree in AGASC1.5 + +Near the galactic poles (b>80deg), where the stellar surface density +is lowest, there are 4.1 stars per square degree. The desired figure +of merit (FOM) of 5.1 per square degree over 95% of the sky is thus +not quite achievable with these selection criteria from current +catalogs, and may not ever be (i.e. we are already nearly complete). +The current Chandra guide star selection includes stars without TYC +colors or PPM SpType information, which boosts the surface density, +but at this limiting ACA magnitude, such colors are available for 98% +of stars. + + +HST Guide Star Catalog +---------------------- + +The HST Guide Star Catalog (GSC), which has been constructed to support +the operational need of the Hubble Space Telescope for off-axis guide +stars, contains 18,819,291 objects in the seventh to sixteenth +magnitude range, of which more than 15 million are classified as +stars. + +The GSC is primarily based on an all-sky, single epoch, single +passband collection of Schmidt plates. For centers at +6 degrees and +north, a 1982 epoch "Quick V" survey was obtained by the Palomar +Observatory, while for southern fields, materials from the UK SERC J +survey (epoch approximately 1975) and its equatorial extension (epoch +approximately 1982) were used. + +Photometry is available in the natural systems defined by the +individual plates in the GSC collection (generally J or V), and the +calibrations are done using B, V standards from the Guide Star +Photometric Catalog. The overall quality of the photometry near the +standard stars is estimated from the fits and other tests to be 0.15 +mag (one sigma, averaged over all plates), while the quality far from +the sequences is estimated from the all-sky plate-to-plate agreement +and from comparisons with independent photometric surveys to be about +0.30 mag (one sigma), with about 10% of the errors being greater than +0.50 mag. + +Astrometry, at equinox J2000, is available at the epochs of the +individual plates used in the GSC; and the reductions to the reference +catalogs (AGK3, SAOC, or CPC, depending on the declination zone) use +third order expansions of the modeled plate and telescope effects. +Estimates of the overall external astrometric error, produced by +comparisons of independently measured positions without regard to +location on the GSC plates, are in the range 0.4 arc-sec to 0.6 +arc-sec. + +Further details concerning the HST GSC can be found in the following +publications: + +1. The Guide Star Catalog. I. Astronomical and Algorithmic + Foundations; Barry M. Lasker, Conrad R. Sturch, Brian J. McLean, + Jane L. Russell, Helmut Jenkner, and Michael M. Shara; + Astrophysical J. Suppl., 68, 1-90 (1988). + +2. The Guide Star Catalog. II. Photometric and + Astrometric Calibrations; Jane L. Russell, Barry M. Lasker, + Brian J. McLean, Conrad R. Sturch, and Helmut Jenkner; + Astronomical J., 99, 2059-2081 (1990). + +3. The Guide Star Catalog. III. Production, Database + Organization, and Population Statistics; Helmut Jenkner, + Barry M. Lasker, Conrad R. Sturch, Brian J. McLean, Michael + M. Shara, and Jane L. Russell; Astronomical, J., 99, + 2081-2154 (1990). + +4. The table rev_1_1.tbl that accompanies the HST GSC1.1, as + prepared by the Space Telescope Science Institute (ST ScI), + 3700 San Martin Drive, Baltimore, MD 21218, USA. + GSC 1.1 analysis and production were performed primarily by + Jesse B. Doggett, Daniel Egret, Brian J. McLean, and Conrad + Sturch. + + + +Positions and Proper Motions Catalog (PPM) +------------------------------------------ + +PPM North gives J2000 positions and proper motions of 181731 stars +north of -2.5 degrees declination. The mean epoch is near 1931. The +average mean errors of the positions and proper motions are 0.27" and +0.43"/cen. On the average six measured positions are available per +star. In addition to the positions and proper motions, the PPM +(North) contains the magnitude, the spectral type, the number of positions +included, the mean error of each component of the position and proper +motion, and the weighted mean epoch in each coordinate. + +PPM South gives positions and proper motions of 197179 stars south of +about -2.5 degrees declination. This net is designed to represent as +closely as possible the new IAU (1976) coordinate system on the sky, +as defined by the FK5 star catalogue (Fricke et al., 1988). + + +Further details concerning the PPM catalogs can be found in the following +publications: + +1. Catalogue of Positions and Proper Motions; Roeser S., & + Bastian U., 1988, Astron. Astrophys. Suppl. 74, 449 + +2. PPM South: A reference star catalogue for the southern + hemisphere; Bastian, U., Roeser, S., Nesterov, V. V., + Polozhentsev, D. D., Potter, Kh. I., 1991, Astron. + Astrophys. Suppl. 87, 159 + + +TYCHO Output Catalog (TYC) +-------------------------- + +Colors are still needed for the majority of stars in AGASC1.1, +since merge with the PPM provided colors (from spectral types) for only +brightest 2% of the GSC1.1 to V=14.5. Also, PPM-derived colors are +probably very uncertain, since they are interpolated from listed +Spectral Types with no reddening information. Merging the Tycho Output +Catalog with the existing AGASC1.1 provides reliable colors for +1,058,332 stars, nearly complete to V=10.5 In the current error +budget, using the highly accurate Tycho star positions should improve +the absolute aspect by 30-50% relative to GSC1.1 positions. + +The Tycho Output Catalog from the Tycho star mapper on the Hipparcos +satellite, provides high precisions astrometric and photometric data +for 1,058,332 stars, nearly complete to V=10.5 Median astrometric +standard errors (in position, parallax, and annual proper motion) are +typically around 7mas for stars brighter than V_T_~9mag, and +approximately 25mas for V_T_~10.5mag, at the catalogue epoch +(J1991.25). Astrometric errors for Tycho stars (typically 25 +milliarcsec), are of the same order as parallaxes expected for many +bright (V<=8) stars typically selected by the Chandra Star Selection +Algorithm. Since parallax is additive, it will dominate absolute +position errors unless incorporated in the Chandra image aspect solution. + +Further details concerning the TYC catalog can be found in the following +publications: + +1. The Tycho Reference Catalogue, Hog, E. et al. 1998, + Astronomy and Astrophysics, 335, L65 +2. The Tycho Catalogue, Hog, E. et al. 1997, + Astronomy and Astrophysics, 323, L57 + +ACT Reference Catalog (ACT) +--------------------------- + +The ACT Reference Catalog contains 988,758 star positions and proper +motions covering the entire sky for the epoch and equinox J2000.0. +The proper motions are from new reductions of the Astrographic +Catalogue combined with the positions in the Tycho Catalogue. +The proper motions of the Tycho stars have thus been improved from about +30~mas/year to about 3~mas/year by recomputing them using the AC2000 +data. This combination of AC2000 and Tycho, called ACT Reference +Catalog, degrades much more slowly and is a valuable astronomical +dataset for applications potentially spanning decades. + +The AC~2000 is a positional catalog recently compiled at The U.S. Naval +Observatory using the plate measures contained in the Astrographic +Catalogue (AC). By the conclusion of the original AC project, +positions of 4.6 million stars had been measured, many as faint as +13th magnitude. These positions have an extremely early epoch; the +average epoch of an AC plate is 1907. To compile the AC~2000, each of +the 22 zones making up the Astrographic Catalogue was reduced +independently using the Astrographic Catalog Reference Stars. + +Further details concerning the ACT can be found in the following +publications: + +1. The ACT Reference Catalog, Urban, S. E., Corbin, T. E., + and Wycoff, G. L. 1998, AJ, 115, 2161 +2. The AC 2000: The Astrographic Catalogue on the System Defined by + the Hipparcos Catalogue, Urban, S.E., et al. 1998, AJ, 115, 1212 + +TYCHO-2 Catalog +--------------- + +The Tycho-2 Catalogue is an astrometric reference catalogue containing +positions and proper motions as well as two-colour photometric data +for the 2.5 million brightest stars in the sky. Components of double +stars with separations down to 0.8 arcsec are included. + +The Tycho-2 positions and magnitudes are based on precisely the same +observations as the Tycho-1 Catalogue (ESA SP-1200, 1997) collected by +the star mapper of the ESA Hipparcos satellite, but Tycho-2 is much bigger +and slightly more precise, owing to a more advanced reduction technique. + +Proper motions precise to about 2.5 mas/yr are given as derived from +a comparison with the Astrographic Catalogue (AC) and 143 other +ground-based astrometric catalogues, all reduced to the Hipparcos +celestial coordinate system. For only about 100,000 stars, no proper +motion could be derived. + +Tycho-2 supersedes Tycho-1, and the ACT and TRC catalogues based on Tycho-1. +The main Tycho-2 catalogue gives positions and at least one of B and V +for all stars at the epoch of observation. For most entries (96%) +proper motions (at epoch 2000) are also derived, using other +catalogues (mainly AC) and the corresponding mean positions at epoch +J2000. When no proper motion has been derived, no mean position for +epoch J2000 is given. Supplement-1 contains stars missing in Tycho-2, +but found in HIP or Tycho-1. The supplement-1 only includes Tycho-1 +stars of good quality and therefore the quality 9 (very poor) stars +and probable side-lobes were not included. + +GSC-ACT Catalog +--------------- + +The original GSC1.1 positions have random position errors of about +0.4arcsec, but also systematic position errors of about 0.3arcsec, +due to errors in the reference catalogs (AGK3, SAO, CPC) and also +to their low stellar density. STScI performed a recalibration of the +GSC1.1, using the PPM catalog for a denser reference star network, +resulting in the GSC1.2: see +http://www-gsss.stsci.edu/gsc/gsc1/gsc12/DESCRIPTION.HTML. + +In the GSC-ACT project, Bill Gray also recalibrated the GSC1.1, +but using the ACT (Astrographic Catalog/Tycho) data from the US Naval +Observatory. In the GSC-ACT, GSC 1.1 systematic errors were reduced +via recalibration of 42 plate coefficients plate-by-plate, using the +proper-motion-corrected ACT stars for reference. +See http://www.projectpluto.com/gsc_act.htm + +Here at the CXC, we matched (2arcsec search radius) both the GSC-ACT +and GSC1.2 against the catalog of ICRS defining source positions. +From 43 independent sources matched, the GSC1.2 showed a mean +positional difference of 0.40arcsec, RMS 0.35. From 44 sources, +the GSC-ACT showed mean 0.28arcsec, RMS 0.25. The denser reference +star network of the GSC-ACT results in a superior calibration, +this is the catalog we've chosen to improve star positions in the +AGASC that had only GSC1.1 (no Tycho or PPM) data. + +2MASS Galaxy Catalog +-------------------- + +We use a pre-release catalog of extended objects from June 2001 +kindly provided by Tom Jarrett (IPAC) and John Huchra (CfA). +The table used contains 41855 such objects, most of which +have not been verified as of this date by the human eye, or by match +to known galaxies. In AGASC1.5, we required that any AGASC object that +has an extended 2MASS object within 5arcsec should have its CLASS +set to 1 (galaxy). 70% of 2MASS galaxies are thus matched. +CLASS=7 is used to denote objects within 3*r20 of 2MASS galaxies, +to mean that the object is close to a galaxy or other extended object. +The 2MASS project is a collaboration between The University of +Massachusetts and the Infrared Processing and Analysis Center (JPL/ +Caltech). Funding is provided primarily by NASA and the NSF. +For information on 2MASS, see http://www.ipac.caltech.edu/2mass/ + +AAVSO Photometric All-Sky Survey (APASS) +---------------------------------------- + +We make use of data from the (American Association of Variable Star Observers (AAVSO) +Photometric All Sky Survey, DR9, +whose funding has been provided by the Robert Martin Ayers Sciences Fund +and by the NSF under grant AST-1412587. We matched the AGASC catalog +with the APASS catalog (2 arcsec search radius) and included a new color +information, V - i aka COLOR3 (APASS) in AGASC 1.7. COLOR2 (Tycho) +combined with COLOR3 (APASS) resulted in improved calibration of the +red spoiler stars. + + +Acknowledgements +================ + +The AXAF Guide and Acquisition Star Catalog version 1.7 was prepared +from AGASC1.6 and AAVSO (American Association of Variable Star Observers) +Photometric All-Sky Survey (APASS) DR9, primarily by Malgosia Sobolewska, +Tom Aldcroft, and Jean Connelly. Thanks to the entire Star Selection and +Aspect Working Group for its input in the development and testing of this +catalog. The Chandra X-ray Center is supported through NASA Contract +NAS8-39073. Information about Chandra and the Chandra X-ray Observatory +Center may be found on the WWW at http://chandra.harvard.edu/ +Detailed information about the catalog and its construction can be +obtained from the Chandra aspect web page at +https://cxc.harvard.edu/mta/ASPECT/agasc1p7 or by emailing: +aspect_help@cfa.harvard.edu diff --git a/docs/index.rst b/docs/index.rst index 8d3a72fe..44c4f0f2 100644 --- a/docs/index.rst +++ b/docs/index.rst @@ -3,14 +3,20 @@ You can adapt this file completely to your liking, but it should at least contain the root `toctree` directive. -AGASC Catalog Description and History -------------------------------------- +AGASC 1.8 Catalog Description and History +----------------------------------------- .. toctree:: :maxdepth: 2 catalog-description +AGASC 1.7 (Previous Version) Readme +------------------------------------- + + :doc:`catalog-description-1p7` + + Getting started --------------- @@ -58,4 +64,4 @@ Topics For Maintainers :maxdepth: 2 supplement - maintainer_api \ No newline at end of file + maintainer_api From 010d30e2097d8922873368d14691c748e9baf036 Mon Sep 17 00:00:00 2001 From: Tom Aldcroft Date: Thu, 25 Jul 2024 14:55:18 -0400 Subject: [PATCH 2/2] Make previous version a line item not section --- docs/index.rst | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/docs/index.rst b/docs/index.rst index 44c4f0f2..3bd2a084 100644 --- a/docs/index.rst +++ b/docs/index.rst @@ -3,18 +3,19 @@ You can adapt this file completely to your liking, but it should at least contain the root `toctree` directive. -AGASC 1.8 Catalog Description and History ------------------------------------------ +AGASC Catalog Description and History +------------------------------------- .. toctree:: :maxdepth: 2 catalog-description +- :doc:`catalog-description-1p7` -AGASC 1.7 (Previous Version) Readme -------------------------------------- +.. toctree:: + :hidden: - :doc:`catalog-description-1p7` + catalog-description-1p7 Getting started