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At the IAU XXVI General Assembly in 2006, the Division I decided to create the Working Group on Astrometry by Small Ground-Based Telescopes (WG-ASGBT). Its scientic goals are to foster the follow-up of small bodies detected by the large surveys including the NEOs; to set-up a dedicated observation network for the follow-up of objects which will be detected by Gaia; to contribute to the observation campaigns of the mutual events of natural satellites, stellar occultations, and binary asteroids; and to encourage teaching astrometry for the next generation. The present report gives the main activities carried out in these areas with small telescopes (diameter less than 2m).

The results of 1683 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. Each speckle interferometric observation of a system represents a combination of over 2000 short-exposure images. These observations are averaged into 805 mean relative positions and range in separation from 023 to 4334, with a median separation of 433. This is the 11th in a series of papers presenting measurements obtained with this system and covers the period 2004 January 4-December 30. Included in these data are two older measurements whose positions were previously deemed possibly aberrant but are no longer classified this way following a confirming observation. Two of these systems have new orbital elements, which are also presented here.

The results of 3047 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. Each speckle interferometric observation of a system represents a combination of over a thousand short-exposure images. These observations are averaged into 1572 mean relative positions and range in separation from 020 to 6286, with a median separation of 419. This is the 10th in a series of papers presenting measures obtained with this system and covers the period 2003 January 13 through 2003 December 1. Included in these data are nine older measures whose positions were previously deemed possibly aberrant but are no longer classified this way following a confirming observation. Four of these systems have new orbital elements, which are presented here as well.

The results of 3056 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. Each speckle interferometric observation of a system represents a combination of over a thousand short-exposure images. These observations are averaged into 1675 mean relative positions and range in separation from 019 to 4521, with a median separation of 299. This is the ninth in a series of papers presenting measures obtained with this system and covers the period 2002 January 1 through 2002 December 29. Included in these data are 28 older measures whose positions were previously deemed possibly aberrant but are no longer classified this way following a confirming observation. Nine of these systems have new orbital elements, which are presented here as well.

New optical positions on the 30 mas precision level have been obtained for 172 extragalactic International Celestial Reference Frame (ICRF) sources mainly in the range -30° ≤ δ ≤ +25°. Results are presented from a pilot investigation including four Cerro Tololo (CTIO) 0.9 m runs (1999–2001). Reference stars in the R ≈ 10–16.5 mag range from a preliminary US Naval Observatory CCD Astrograph Catalog (UCAC) are used. Systematic errors have been investigated, and a field distortion pattern based on the residuals has been removed. The errors of the fainter stars in the CTIO data were assessed by evaluating an auxiliary set of CCD observations of common ICRF sources, taken at the 1.60 m Cassegrain telescope of the Laboratorio Nacional de Astrofisica, Brazil. A significant improvement in the optical positions was achieved over a previous determination of source positions. The mean optical positions are compared with the ICRF radio positions. The overall optical minus radio offsets are -6 and -15 mas for right ascension and declination, respectively. The formal internal error of these mean offsets is ≈2.3 mas. This indicates a possible systematic error in the UCAC declinations of ≈10 to 15 mas. Both the optical counterpart observations and the optical reference stars are observed about 9 yr after the Hipparcos mean epoch, and our results set an upper limit for a possible Hipparcos system rotation with respect to the International Celestial Reference System for the z-axis of about 0.7 mas yr-1.

The results of 2044 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. Each speckle interferometric observation of a system represents a combination of over a thousand short-exposure images. These observations are averaged into 1399 mean positions and range in separation from 016 to 1497, with a mean separation of 251. This is the eighth in a series of papers presenting measures obtained with this system and covers the period 2001 March 18 through 2001 December 30.

The results of 2014 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. These observations are averaged into 1266 mean positions and range in separation from 021 to 1341, with a mean separation of 261. This is the seventh in a series of papers presenting measures obtained with this system and covers the period 2000 January 10 through December 8.

The Hipparcos satellite made measurements of over 9734 known double stars, 3406 new double stars, and 11,687 unresolved but possible double stars. The high angular resolution afforded by speckle interferometry makes it an efficient means to confirm these systems from the ground, which were first discovered from space. Because of its coverage of a different region of angular separation–magnitude difference (ρ-Δm) space, speckle interferometry also holds promise to ascertain the duplicity of the unresolved Hipparcos "problem" stars. Presented are observations of 116 new Hipparcos double stars and 469 Hipparcos "problem stars," as well as 238 measures of other double stars and 246 other high-quality nondetections. Included in these are observations of double stars listed in the Tycho-2 Catalogue and possible grid stars for the Space Interferometry Mission.

The USNO CCD Astrograph (UCA) started an astrometric survey in 1998 February at Cerro Tololo, Chile. This first, preliminary catalog (UCAC1) includes data taken up to 1999 November with about 80% of the Southern Hemisphere covered. Observing continues, and full sky coverage is expected by mid-2003 after moving the instrument to a Northern Hemisphere site in early 2001. The survey is performed in a single bandpass (579–642 nm), a twofold overlap pattern of fields, and with a long and a short exposure on each field. Stars in the magnitude range 10–14 have positional precisions of ≤20 mas. At the limiting magnitude of R ≈ 16 mag, the positional precision is 70 mas. The UCAC aims at a density (stars per square degree) larger than that of the Guide Star Catalog (GSC) with a positional accuracy similar to Tycho. The UCAC program is a major step toward a high-precision densification of the optical reference frame in the post–Hipparcos era, and the first stage, the UCAC1 contains over 27 million stars. Preliminary proper motions are included, which were derived from Tycho-2, Hipparcos, and ground-based transit circle and photographic surveys for the bright stars (V ≤ 12.5 mag) and the USNO A2.0 for the fainter stars. The accuracy of the proper motions varies widely, from 1 to over 15 mas yr-1. The UCAC1 is available on CD-ROM from the US Naval Observatory.

The results of 1068 speckle interferometric observations of double stars, made with the 26 inch (0.66 m) refractor of the US Naval Observatory, are presented. These observations are averaged into 841 means of 815 binary stars. The systems range in separation from 022 to 601 with a mean separation of 221 and have a limiting secondary magnitude of V = 12.5. This is the sixth in a series of papers presenting measures obtained with this system, and it covers the period 1999 January 1 through 2000 January 9.

The results of 1544 speckle interferometric observations of 637 binary stars, ranging in separation from 025 to 525, are tabulated. These observations were obtained using the 66 cm refractor at the US Naval Observatory in Washington, DC, with an intensified CCD detector. This is the fifth in a series of papers presenting measures obtained with this system and covers the period 1998 January 1 through December 31. Random errors for all measures are estimated to be 17.6 mas in separation and 055/ρ in position angle, where ρ is the separation in arcseconds.

A new, highly accurate, astrometric star catalog is available from the U.S. Naval Observatory, covering ≈ 80% of the Southern Hemisphere to R ≈ 16m. The observing program is ongoing and full-sky coverage is expected by 2003. The final catalog will be used as the input catalog for the FAME space mission.

Between the years 1985 and 1996 the U.S. Naval Observatory (USNO), using two transit circles, one located in Washington, DC (U.S.A.) and the other in Blenheim, New Zealand, conducted an ambitious program of absolute observations of positions of celestial objects completely covering both hemispheres. Over 737 000 individual observations were made, primarily of the International Reference Stars (IRS) and FK5 stars, as well as all the major planets (except Pluto) and thirteen minor planets. This included some 55 000 observations of day-time objects including the Sun, Mercury, Venus, and Mars. The original objective was to form a traditional, all-sky catalog of absolute star positions which could be firmly linked to the dynamical system. However, with the success of the Hipparcos project and the adoption of the ICRF as the celestial reference frame, the primary focus of the pole-to-pole program changed. The stellar positions have been differentially reduced to the system of Hipparcos and these were used to tie the planetary observations into the ICRF. Thus the program has resulted in a body of high quality observational data (average standard deviation of a mean position of about 75 mas) that will provide important input for the production of ICRF-based ephemerides. This is particularly true for the outer and minor planets.

A new method of dening the declination axis of the instrumental frame of an absolute transit circle cat- alog has been developed utilizing observations from stars over the entire sky rather than, as in the past, observations of just circumpolar stars. This method allows the plane- tary observations to be used directly to align the axes of the instrumental frame thus constructed with DE200. The alignment process has been simplied and recast so that it does not feed back into the denition of the in- strumental frame. A declination oset, which is unique to absolute transit circle observational catalogs, is discussed emphasizing the problem of its cross-correlation with ro- tation terms from the alignment process. When compared to \traditional" methods, these new procedures give sim- ilar results for those quantities in common but they also produce additional adjustments that were not accounted for previously.

The results of 2408 intensified CCD observations of double stars, made with the 26 inch refractor of the U.S. Naval Observatory, are presented. Each observation of a system represents a combination of over 2000 short-exposure images. These observations are averaged into 1602 mean relative positions and range in separation from 194 to 10741, with a median separation of 1196. This is the twenty-first in this series of papers and covers the period from 2015 January 13 through 2015 December 19. Significant instrumentation changes are reported in this paper.

URAT1 is an observational, astrometric catalog covering most of the δ −15° area and a magnitude range of about R = 3–18.5. Accurate positions (typically 10–30 mas standard error) are given for over 228 million objects at a mean epoch around 2013.5. For the over 188 million objects matched with the Two Micron All Sky Survey (2MASS) point-source catalog proper motions (typically 5–7 mas yr–1 standard errors) are provided. These data are supplemented by 2MASS and AAVSO Photometric All-Sky Survey (APASS) photometry. Observations, reductions, and catalog construction are described, together with results from external data verifications. The catalog data are served by CDS, Starsbourg (I/329).

Results are presented for 353 speckle interferometric observations of double stars, obtained in 2003 and 2004 at the USNO Flagstaff Station using the 1.55 m Kaj Strand Astrometric Reflector. Separations range from 012 to 742, with a median of 042. These two observing runs concentrated on systems in need of improved orbital elements, and new solutions have been determined for 17 systems as a result.

Fundamental meridian circle observations require the variation of latitude to be applied before the observations are combined to form a catalogue. In the past 80 years, different observatories have used various determinations of polar motion to reduce their observations. This study shows that the use of different determinations of the latitude variation significantly affects the individual observations and can introduce large zonal errors of the level of 0.05 seconds of arc into the catalogue's declination system.

Fundamental meridian circle observations require the variation of latitude to be applied before the observations are combined to form a catalogue. In the past 80 years, different observatories have used various determinations of polar motion to reduce their observations. This study shows that the use of different determinations of the latitude variation significantly affects the individual observations and can introduce large zonal errors of the level of 0.05 seconds of arc into the catalogue’s declination system.