Hola Javier, Nos has matado con lo de "chorra"
Si por chorra quieres decir sencillo de usar, tienes razón, es chorra. Incluso como comenta Gusgus hay un programa, doméstico que realiza el borrado de estrellas una vez el Astrométrica indica el número de catálogo y magnitud estimada de cada estrella. Lo puedes obtener en Focas. La única limitación es que estima la magnitud del cometa en circulos de 10, 20, 30, 40, 50, y 60 segundos de arco.
La opción del Track and Stack de Astrmétrica te puede realizar el alineamiento de imágenes teniendo en cuenta la velocidad y dirección del cometa.
He visto, que no usado, como el Iraf calcula aperturas a discreción, pero no tengo el iraf. Muchísimo programa para mi, y muy complicado de instalar incluso en Linux (S.O. que tengo, por que sueño con poder usar el IRAF alguna vez).
Que tengas mucha suerte...
Por cierto me he encontrado con la lista de usuarios registrados de astrométrica. Me imagino la no registrada

....
Aguirre Edwin L., "Sky & Telescope", USA
Aikman Chris, Dominion Astrophysical Observatory, Canada
Arce Enrique, Vallbona Observatory, Spain
Astroclubul Bucuresti, Romania
Agrupacio Astronomica de Sabadell, Spain
Ates Alper, Pomona Colloege, USA
Amateur Astronomers Association Seulaset, Finland
Andresson Sven, Germany
Andrushivka Astronomical Observatory, Ukraine
Apitzsch Rudolf, Wildberg Observatory, Germany
Asami Atsuo, Hadano Observatory, Japan
Associazione Astrofili Mantovani, San Benedetto Po Observatory, Italy
Astronaut Memorial Planetarium and Observatory, Brevard Community College, USA
Atlante Observatory, Spain
Bachleitner Hannes, Austria
Ball Loren, Emerald Lane Observatory, USA
Barentine John, Apache Point Observatory, USA
Bartholomew Clarence, Woden World Observatory, U.S.A.
Bedient Jim, U.S.A.
Behrend Raoul, Observatoire de Genève, Switzerland
Beresford Tony, Australia
Birtwhistle Peter, Great Shefford Observatory, England
Bisophere 2 Center, USA
Bittesini Luciano, Farra D'Isonzo Observatory, Italy
Boattini Andrea, Spaceguard Central Node, Italy
Boles Tom, Coddenham Astronomical Observatory, UK
Buck Michael, Germany
Buzzi Luca, 'G.V.Schiaparelli' Observatory, Italy
Brewster Steve, Stony Ridge Observatory, USA
Briggs John W., Yerkes Observatory, USA
Cahill Alan, Abbeydale Observatory, UK
Campocatino Astronomical Observatory, Italy
Campo Imperatore NEO Survey, Italy
Chumack John, Chumack Observatory, USA
Clayden Andre, Springbrook Observatory, Australia
Cordell-Lorenz Observatory, University of the South, USA
Cornell, David A., Principia College Observatory, USA
Daiber Torsten, Germany
Dawson Matt, Roeser Observatory, Luxembourg
Dymock Roger, BAA Asteroids Section, UK
diCicco Dennis, "Sky & Telescope", USA
Dillon Bill, Fort Bend Astronomy Club, USA
Dixon David, Jornada Observatory, USA
Donati Sauro, Italy
Doppler Andreas, DANEOPS, Germany
Emmerich Mark, Germany
Endate Kin, Japan
Farmer Steve E., jr., USA
Faulkes Telescope, Hawaii and Australia
Ferrando Rafael, Observatorio Astronomico Pla D'Arguines, Spain
Fiedler Martin, Astroclub Radebeul, Germany
Fink Uwe, Lunar and Planetary Lab, USA
Fletcher John, Mount Tuffley Observatory, UK
Franch Penas Xavier, I.E.S. Maria Rúbies, Spain
Genebriera Joan, Tacande Observatory, La Palma, Spain
Geneva Astronomical Society, France
George Observatory, USA
Gierlinger Richard, Austria
Gnädig Arno, DANEOPS, Germany
Greiner Research Observatory, USA
Griesser Markus, Eschenberg Observatory, Switzerland
Groom Roger, Australia
Hahn Gerhard, German Aerospace Center (DLR), Germany
Hammergren Mark, Adler Planetarium, USA
Hasubick Werner, Buchloe Observatory, Germany
Hergenrother Carl, Catalina Sky Survey, USA
Hernandez Rafael Pacheco, Observatori Astronomic de Consel, Spain
Higgins David, Hunters Hill Observatory, Australia
Holvorcem Paulo, Valinhos Observatory, Brazil
Hug Gary, Farpoint Observatory, USA
Hund Friedhelm, International Amateur Observatory, Namibia
Husar Dieter, Himmelsmoor Private Observatory, Germany
International Astronomical Search Collaboration, U.S.A and other countries
Jacques Cristovao, Wykrota Observatory CEAMIG, Brazil
JAT Observatory, USA
Joao Gregorio, AstroGregas, Portugal
Jones Gilbert, Three Buttes Observatory, USA
Jones Richard, Francisquito Observatory, USA
Julia Josep, Marxuquera Observatory, Spain
Kelemen Janos, Konkoly Observatory, Hungary
Kilmartin Pam, Mt. John University Observatory, New Zealand
Knöfel André, DAPS, Germany
Kocher Peter, Tentlingen Observatory, Switzerland
Koff Bob, USA
Korlevic Korado, Visnjan Observatory, Croatia
Koschny Detlef, European Space Agency (ESA/SSD), Netherlands
Kojima Takuo, Japan
Kowalski Richard, Quail Hollow Observatory, USA
Lacruz Juan, La Canada Observatory, Spain
Lagerkvist Claes-Ingvar, UDAS, Sweden
Learmonth Solar Observatory, Australia
Lehmann Gerhard, Drebach Observatory, Germany
Loucks Scott, LAMP Observatory, USA
Lund Observatory, Sweden
Makino Ikufumi, Japan
Manek Jan, IOTA/ES, Czech Republic
Manno Kent, Delbarton School, USA
Mannucci Massimiliano, Associazione Astrofili Fiorentini, Italy
Manteca Pepe, Observatorio de Begues, Spain
Masi Gianluca, Bellatrix Astronomical Observatory, Italy
Massaro Salvo, Omega Lab, Italy
Max Planck Institute for Extraterrestrial Physics, Germany
Mc Carthy Observatory, USA
McCullough Peter, Project Stardial, USA
McGaha James, Grasslands Observatory, USA
McNaught Robert, Anglo-Australian Observatory, Australia
Meister Stefan, Sternwarte Bülach, Switzerland
Michelsen René, Copenhagen University Observatory, Denmark
Mihelcic Matej, Vega Observatory, Slovenia
Mills Elgie, Ogden Astronomical Society, USA
Mobberley Martin, Cockfield Observatory, UK
Modra Observatory, Slovakia
Morris Charles, Dream Weaver Observatory and Comet Observation Home Page, USA
Naves Nogues Ramón, , Observatorio Montcabrer, Spain
New Mexico Skies Observatory, USA
Observatori Astronòmic de Mallorca, Spain
Observatorio Astronómico Municipal Monte Deva en Gijon, Spain
Ögmen Yenal, Green Island Observatory Homepage, North Cyprus
Ory Michel, l'Observatoire astronomique jurassien, Switzerland
Osborn Wayne, Central Michigan University, USA
Pack Hughes, Project Hands-On Universe, USA
Pelloni Andrea, Associazione Romana Astrofili, Italy
Peña Antonio, Tres Cantos Astronomical Observatory, Spain
Petr Pazour, The Vlasim Astronomical Society, Czech Republic
Perez Silvia Alonso, Tenerife, Spain
Pognat Paolo, Grange Observatory, Italy
Potter Andrew, Lunar and Planetary Institute, USA
Prosperi Enrico, Castelmartini Observatory, Italy
Powell Observatory, USA
Puckett Tim, Puckett Observatory, USA
Racz Miclos, Konkoly Observatory, Hungary
Rausch Gerhard, Schulsternwarte Gudensberg, Germany
de los Reyes-Garcia José, Observatorios de la Región de Murcia, Spain
Rhemann Gerald, Astrostudio, Austria
Ries Wolfgang, Privatsternwarte Seng, Austria
Robertson Jeff, Arkansas Tech University, USA
Rodríguez, Gustavo D., Asociacion Argentina Amigos de la Astronomia, Argentina
Sánchez Joaquín, Observatorio El Mirador de Murcia, Spain
Santallo Roland, Southern Stars Observatory, Tahiti
Science Learning Centre Soth East, University of Southampton, UK
Schwartz Michael, Tenagra Observatories USA
Serrau Marc, France
Simonetti John, Virginia Tech Observational Astrophysics Course", USA
Sinnott Roger W., "Sky & Telescope", USA
Sollee Neyle, Sangre Observatory, USA
Spaceguard India, India
Sposetti Stefano, Switzerland
Spratt Chris, Canada
Starkenburg-Sternwarte Heppenheim, Germany
Stevens Bert, Desert Moon Observatory, USA
Stogneeva Irina, Odessa Astronomical Observatory, Ukraine
Sturm Christian, Germany
Tancredi Gonzalo, University of Montevideo, Uruguay
Tate Jonathan, Spaceguard Centre, UK
Thinius Bernd, Inastars Observatory Potsdam, Germany
Tholen David, Institute for Astronomy, University of Hawaii, USA
TOPS Workshop, University of Hawaii, USA
Tucker Roy A., Goodricke-Pigott Observatory, USA
Turtle Star Observatory, Germany
University of Durham, UK
US Air Force Academy Observatory, USA
Vail Jim, USA
Vergara Antoine, Lentin Observatory, France
Villi Mirko, International Supernovae Network
Vsetin Observatory, Czech Republic
Walter Johannes, Wachtberg, Germany
Ward Dennis, The Silicon Sky, USA
Warell Johan, Uppsala Observatory, Sweden
Weissman Paul, Jet Propulsion Laboratory (JPL), USA
Williams Gareth, Minor Planet Center, USA
Wise Observatory, Israel
Yerkes Observatory, USA
Young James W., Table Mountain Observatory, USA
Yusa Toru, Japan
Yuste Miguel Camarasa, L'Observatori d'Ontinyent, Spain
Zattera Flavio, Stazione Astronomica "CorCaroli", Italy