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Engine Front-end/ installer License External access Blind solving 360° (off line) Cloud access to nova.astrometry.net MS-Windows (X86) Linux (X86) Linux (ARM)
Currently, astrometric solving is exclusively done by software programs. The program extracts the star x,y positions from the celestial image, groups them in three-star triangles or four-star quads. Then it calculates for each group a geometric hash code based on the distance and/or angles between the stars in the group.
Illustration of the use of interferometry in the optical wavelength range to determine precise positions of stars. Courtesy NASA/JPL-Caltech. Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies.
Astrometry has been used to discover a handful number of exoplanets, mostly gas giants more massive than Jupiter. It is based on measuring a star's proper motion, and seeing how that position changes over time: a planet with a sufficiently large mass is able to gravitationally pull its host star, making its proper motion vary over large timescales.
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An initial rough alignment is first performed using the polar scope. An image can then be captured and a star database is used to identify the exact field of view when aimed at stars near the pole - 'plate solving'. The telescope is then rotated ninety degrees around its right ascension axis and a new 'plate solve' is carried out.
The PPM can be considered a replacement of two preceding astrometric catalogs which served a similar purpose: AGK3 and the SAO Catalog. In contrast to the PPM, these older catalogs are based on (1) the now obsolete FK4 system of positions and proper motions, and (2) only two position measures per star.
New 1 in Cetus (source: The Deep-Sky Field Guide to Uranometria 2000.0, Cragin-Lucyk-Rappaport, chart 262). New 5 in Sagittarius (thus mentioned on chart 22 of Wil Tirion's Sky-Atlas 2000.0, mentioned as ESO 285-G7 on charts 411 and 412 in Uranometria 2000.0 Volume 2, 1987 edition).