[#1] HOW AMATEURS HAVE CONTRIBUTED TO ASTEROID RESEARCH The title of my presentation this evening is "How Amateurs Have Contributed to Asteroid Research, subtitle A Case Study in Outstanding Pro-Am Collaboration. In modern times life is easy. [#2] Click on any moving or stationary target, click Go To, wait a few seconds, take an image, and there is the specified target right in the center of the field. This works just as well for any minor planet, or asteroid. MPO Connections software provides a star chart of the target field at the left, the CCD image at the right. I give you a few seconds to find the image of the asteroid, 65 Cybele, which is not on the star chart. [#3] It wasn't always this easy. Asteroids are pointlike objects indistinguishable from stars at first glance. Until about 1968 it required laboriously constructing a diagram of all the stars in a large field, then waiting a few hours or to the next night to find which one moved. This of course is a recent CCD image, but it illustrates the dilemma of early visual observers. Which object is the asteroid 99 Dike? In old times the observer had to wait a few hours to see which one moved. [#4] Here we'll speed things up and show another CCD image taken a few hours later and identify the moving asteroid. And now we'll use the blinker [3, 4 several times] to make it much easier for you in the audience than it ever was for the old time visual observers. People occasionally looked for Ceres, Pallas, or Vesta, the brightest asteroids, and used the Skalnate Pleso or Webb's atlas to identify the object in the sky which was missing from the chart. The other asteroids went unobserved. What was needed was a star atlas that showed much fainter stars. Such an atlas was Hans Vehrenberg's photographic "Atlas Falkau" showing stars to magnitude 13, or "Atlas Stellarum" showing stars to magnitude 14 or 15. [#5] Early in 1968 I inquired to the Institute for Theoretical Astronomy, Leningrad, then in the USSR, about their annual "Ephemerides of Minor Planets." ITA kindly sent a complimentary copy. [#6] Here is a typical page of their asteroid ephemerides. I plotted the path of asteroid 3 Juno against the star background of the Atlas Falkau. [#7] Immediately I recognized it in the telescope field by its absence on the star chart. The same technique worked for other asteroids. To be confident I always reobserved a few hours later or on subsequent nights to make sure that the suspected object moved along the predicted path. When the object moved as predicted, I knew I had correctly identified the asteroid. Sometimes, more often for very faint objects, the suspect didn't move, and I had made a misidentification. This procedure for confirming identifications from the predicted motion is necessary for all visual observations of asteroids. I wrote a short letter to Sky and Telescope which was duly published. [#8] One of my early correspondents about observing asteroids was Dr. J. U. Gunter, chief pathologist at the Duke University Medical School and an amateur astronomer. He adopted my method for finding and identifying asteroids in the sky from their absence on the Vehrenberg atlas. [#9] More importantly, he began publishing "Tonight's Asteroids," in which he plotted asteroid positions directly on photocopies from the Atlas Falkau. Now that we had shown how asteroids were easily identified in the sky, many amateurs started observing them. Beginners used the finder charts in Tonight's Asteroids. More advanced observers had to draw their own charts. Some people observe as many as possible of the Messier or Herschel objects. Now a few dedicated visual observers began tracking down as many asteroids as possible. For many years I was one of them. [#10] The grand champion visual observer of asteroids is G. Roger Harvey of Concord, North Carolina. In 1973 he listened to a talk by J. U. Gunter and began an epochal hobby of visually observing asteroids with a 21 inch, and later a 29 inch, back yard telescope. In the year 2010 he passed the 5000 asteroid total, including all of the first 1000 to be numbered. In these days when people increasingly utilize CCDs rather than visual observing, Roger's record is one which may never again be approached. Three other amateurs whose visually observed asteroid total exceeds 2000 are Gerard Faure, Ben Hudgens, and Andrew Salthouse. [#11] The year 1973 was a pivotal one in which an organization for coordinating amateur asteroid activities was created. Richard Hodgson founded the Minor Planets Section of the ALPO and began publishing the quarterly Minor Planet Bulletin. Since that time membership in the Minor Planets Section and a subscription to the Minor Planet Bulletin have been a single activity. From the first issue abstracts of all articles in the Minor Planet Bulletin have been listed in the ADS abstracts. In the early years reports of approximate visual positions, magnitude discrepancies, announcements of asteroids which like Mars have occasional unusually favorable oppositions, and some historical notes dominated the pages of the Minor Planet Bulletin. I was invited to become a charter member, and immediately began contributing articles. Another early member with whom I began communicating was Richard Binzel, then an enthusiastic high school student. From 1973 to 1981 Richard Hodgson held all positions in the Minor Planets Section - Section Recorder, treasurer, publisher and distributor of the Minor Planet Bulletin. In 1982 he resigned all positions. I thank Richard Binzel, by then a graduate student, for the survival and subsequent flourishing of the Minor Planets Section. I became Section Recorder (now called Coordinator), Binzel became publisher of the Minor Planet Bulletin, Bob Werner producer of the Minor Planet Bulletin, and long term ALPO member Derald Nye distributor. Richard Binzel has become one of the leading professional astronomers specializing in minor planet studies. He is very active in amateur-professional cooperation, and the Minor Planet Bulletin has grown to become a leading medium for this cooperation. The Section also has for scientific advisors two of the leading professionals in the field of photometry and lightcurve analysis, Alan Harris and Petr Pravec. In the early 1970's amateur and professional astronomers alike began noticing that they could not find all of the asteroids that should have been easily bright enough for their equipment. The reason was that computerized orbit calculation was still in its infancy, and the published orbits and ephemerides were sometimes significantly in error. By searching up to 2 degrees from the predicted position I and others sometimes found the errant asteroid, which could be confirmed by its moving parallel to its predicted path. In other cases we could not find the desired asteroids and could not add them to our personal lists. Even as we visual observers detected these deficiencies they were being corrected. This was achieved both through increasing observational attention by wide field surveys, and by increasing computer power. Since about the year 1980 I have received no reports of appreciable discrepancies of asteroid positions for any numbered asteroids. [#12] This is a triumph of astrometry, the measurement of precise positions of both fixed and moving objects, especially for moving objects at precisely measured times. Astrometry is the foundation of all of astronomy. In order to study anything else, one must first know where the object is in the sky. It is also a triumph of the celestial mechanics of orbit calculation, which can now be done millions of times faster than in the days of logarithm tables. [#13] The man who facilitated this giant leap forward in computerized minor planet orbit calculation was Brian G. Marsden. Prior to the late 1980's asteroid positions were measured relative to nearby stars on photographic emulsions. This required measuring engines with micrometer accuracy. Such machines were often not available to amateurs, and their contributions were at first few. Among amateur observers during the period from 1980 to 1993 Japanese observers dominated pre-CCD astrometric asteroid observation and are credited as the discoverers of several thousand numbered asteroids. Then in the early 1990s development and availability of the CCD, digitized astrometric catalogs, the personal computer and appropriate software, and the Internet, completely revolutionized the amateur astronomer's capabilities and role. At the same time as amateur activities were changing, huge survey programs were established in a Congressionally backed mandate to find all potential Earth impactors. These surveys produced thousands of asteroid astrometric observations each night. Brian G. Marsden was director of the Minor Planet Center from 1978 to 2006. During Marsden's nearly 30 year tenure as Director numbered asteroids increased from less than 2100 to nearly 200,000, with more than 270,000 numbered as I make this presentation. All sky surveys by LINEAR (Socorro), LONEOS (Lowell Observatory), Spacewatch (Kitt Peak), Catalina Sky Survey (Tucson), and others, which began in the 1990's, are responsible for most of these discoveries. [#14] Even with their huge volumes of accurate astrometric observations these surveys have limitations because of geographic locations and observational cadance. Dr. Marsden recognized even before they became operational that their astrometric observations would not be sufficient by themselves to calculate orbits for some observed objects. In January 1996 a paper authored by D. I. Steel and B. G. Marsden titled "Astrometry of near-earth objects using small telescopes" was presented at the UN/ESA Workshop on Basic Space Science: From Small Telescope to Space Mission at Colombo, Sri Lanka, Dr. Marsden continued dialogs with both the amateur and professional observer communities keeping them informed on MPC status and needs, enhancing the web site to better support observer astrometry, especially by amateurs. Also at this time frame journalist / amateur astronomer Dennis di Cicco (Sky Publishing - Sky and Telescope) was completing an experiment in Minor Planet discovery with amateur equipment and writing an article on his results. The article simply titled "Hunting Asteroids" was published in the CCD Astronomy Spring 1996 issue. The article outlined the details of equipment, software and methodology used in the experiment at his amateur observatory. He concluded that it was entirely practical to conduct an observing program of asteroid discovery with amateur equipment at a home observing site with (at the time) almost certain probability of success. The article captured the interest of a large number of amateur astronomers who began to implement their own programs. One of the first American amateurs to begin supplying the Minor Planet Center with large numbers of sufficiently precise positions was Paul Comba, observatory code 684, who submitted 14,674 observations between 1994 and 2003 with 623 numbered discoveries. [#15] In 1990 134 observatories were reporting observations to the MPC. By 2000 the number had risen to 315 observatories with the majority of the increase being amateur sites. By 2010 the number was 441 observatories. World wide amateur asteroid discoveries went from 910 in 1992, of which only 5 were CCD discoveries, to 5070 in 2009. At the current time amateur observatories submit over 200,000 observations to the Minor Planet Center annually. It is perhaps unfortunate that these amateurs labor in anonymity. Their observations are sent to the Minor Planet Center for cataloging, and other than an occasional MPEC concerning an NEO or Comet are published nowhere else. With both the NEO surveys and a major increase in amateur sites the population of undiscovered asteroids which have average magnitudes bright enough for discovery by amateur equipment becomes smaller each year. For astrometry this has meant either increase sky coverage or increase the limiting magnitude for asteroids, or not focusing on discovery. The majority of amateur asteroid astrometry observatories have chosen to capitalize on the schedule freedom of an amateur observatory and focus on asteroid/comet follow up and object confirmation while some obsevatories have focused on survey/discovery. Progress in the software available to amateur observatories has allowed automation of observatory operations, remote observing over the Internet, and image processing and measurement which has enabled significant increases in sky coverage. [#16] For example one group of amateurs established the Observatorio Astronomico de La Sagra (OLS) observatory in Spain. On site operations and much of the maintance is done by professional observatory personal from Observatorio Astronomico de Mallorca. The equipment is amateur, with three 0.45m telescopes with CCD cameras. The La Sagra Sky Survey LSSS team members in Spain, Croatia, and Hong Kong control the entire data acquisition and data reduction remotely via the Internet. Between 2004 and 2010 LSSS submitted over one million observations to the MPC and by the end of 2010 had over 600 numbered asteroid discoveries 4 comet discoveries and discovery designation of 33 NEOs. Object confirmation and follow-up have been and remain major activities of a number of amateur and some professional observatories. The number of amateur observatories, their wide spread geographical locations and relatively flexible schedules has made confirmation and follow-up areas where amateurs have made significant contributions. The MPC has gone to considerable effort to provide a system to allow an observatory planning to begin an observing session to inquire about suspected NEO or Comet objects needing confirmation or immediate observations and also to allow observatories planning follow up to identify objects which match the observatory's criteria for brightness, apparent motion, sky location, and ephemeris uncertainty. [#17] Herbert Raab's Astrometrica software has evolved from its initial basic DOS package used in the mid and late 1990s which provided image plate solution, blinking, and measurement capabilities. It has become a Windows based package adding moving object detection and shifting of successive images for object motion and co-adding of images which allowed amateur sized 0.3 to 0.6 meter telescopes to successfully support astrometric follow-up of objects being detected by the 1 meter and larger survey telescopes. [#18] The Minor Planet Mailing List MPML was started in 1998 by Richard Kowalski, then an amateur and now an observer with the Catalina Sky Survey. The MPML rapidly became a major venue for the exchange of information, techniques, observation needs about minor planets and comets between both the professional and amateur communities. Many amateur observatories preparing for programs on astrometry and photometry received tutoring from both professional and other amateurs on equipment and techniques. Other institutional observing programs such as the JPL NASA Asteroid Radar Research program routinely makes requests on MPML for astrometry and light curves to assist planning for radar observations of asteroids. When weather or time constrain observations at a site the need for measurements is often communicated on the MPML. A sideline, but a very informative one, is the posting by Ron Baalke of many NASA technical and semi-technical news releases. These always make fascinating reading. [#19] Also in the 1970's we amateurs were finding significant numbers of asteroids for which the magnitudes differed appreciably from those predicted. At the same time professionals were measuring asteroid magnitudes with photoelectric precision. And the amateurs were providing the same magnitude corrections as the photoelectric measurements by professionals were posting on the official lists. Asteroid magnitudes are estimated by comparison with other asteroids in other fields whose predicted magnitudes are assumed correct. This is more challenging than the AAVSO method of comparison with standard stars in the same field. Extensive experience has shown that accuracy of about 0.3 magnitude can be achieved with some regularity. This program has grown into the Magnitude Alert Program (MAP) coordinated by Gerard Faure and Lawrence Garrett, and is exclusively an amateur activity. Many participating observers send emails to Lawrence when in the course of their routine surveys they find a magnitude discrepancy. He in turn sends out mass emails to all participants, with the request that they confirm the discrepant magnitude. MAP has set a limit of 0.3 magnitudes as the nominal accuracy of visual out-of-field estimates, and for smaller discrepancies no effort to correct the catalog values is made. The observations have been analyzed by Gerard Faure with professional thoroughness. At present there is a list of more than 20 asteroids for which the discrepany has been consistent through three or more oppositions, and these we consider to be secure. More than 100 others are on a preliminary list, awaiting confirmation at future oppositions. I will now discuss asteroid rotation studies, which have in recent years become a field of extensive amateur participation. [#20] For a rotating elongated asteroid the brightness increases and decreases twice for each rotation. The time interval between alternate maxima is the rotation period. The difference between maximum and minimum light is called the amplitude, and a larger amplitude indicates a greater elongation for the rotating body. The graph of magnitude versus time is called the lightcurve. Historically the first well publicized lightcurve was made of Eros during its close approach in 1931. Eros' brightness was observed to vary up and down by 1.5 magnitudes twice in 5.27 hours, revealing both its rotation period and a length three times as great as the width. The systematic study of asteroid rotation did not begin until about 1950 when Gerard Kuiper and his students utilized the photoelectric photometer on bright asteroids. They found mostly short rotation periods with amplitudes usually less than 0.5 magnitude. Other professional astronomers followed Kuiper's lead. By 1980 rotation periods had been found for about 300 asteroids, mostly by professionals using photoelectric photometers, and by the year 2000 for about 800 asteroids. [#21] Near the end of the twentieth century three new technological advances made asteroid lightcurve work ten times easier and cheaper than it had been previously with the 1P21 photoelectric photometer. These were: (1) Go To telescope controls including an automatic asteroid ephemeris calculator (2) the CCD camera (3) powerful data reduction software Amateurs began to enter the field in increasing numbers. The Minor Planet Bulletin was an already available medium for publication, and the size of a single issue grew eight-fold between 1998 and 2008. Most of these pages have been rotational lightcurve papers by amateurs. Amateurs in recent years have been publishing papers just as good as the professional papers of earlier decades, and often with much better data sets. Asteroid lightcurve work is very intensive of telescope time. With private, dedicated observatories amateurs can devote the extra time needed for difficult targets which professionals previously could never obtain from observatory scheduling committees. In the year 2010 90% of all published lightcurves were in the Minor Planet Bulletin. At the observational level, the data acquisition process, amateurs now dominate the field. Professional astronomers rely on their data. The Minor Planets Section now occupies a position in the field of asteroid rotation studies comparable with that occupied by the AAVSO in variable star work. [#22] A central on-line repository, the Asteroid Lightcurve Data Base, has been established. This catalog contains lists of rotation periods and amplitudes, related tables of spin axes, orbital parameters for binary asteroids, tumbling asteroids, reliabilities of all of these parameters, and thousands of references to the published literature. We should note that a lightcurve taken near a single opposition shows the synodic period, not the sidereal period. And the observed amplitude depends upon the aspect, the angle between line of sight and initially unknown rotation axis. Usually the amplitude is maximum for equatorial aspect and zero if the line of sight is toward the pole. It requires observations at several different locations around the sky to determine the sidereal period, rotation axis, and shape. [#23] I illustrate with three lightcurves I have obtained for 161 Athor at three successive oppositions. All show nearly the same rotation period but have completely different shapes. The upper left shows the usual two maxima and minima per rotational cycle and appears to represent near equatorial aspect. The very small amplitude, only 0.03 magnitude, at the upper right shows that the target was at near polar aspect. This shows than one of the two rotational poles is only a few degrees from the position in the sky at the time of observation. The lower lightcurve shows only one maximum and minimum per rotational cycle. This is commonly observed ten to thirty degrees from polar aspect and is caused by the asteroid being shaped more like a pear than a perfect ellipsoid. The brightness increases as the thick end rotates toward the observer and decreases as it rotates toward the far side of the object. [#24] By inputting lightcurves at different locations in the sky into a computation intensive computer technique known as lightcurve inversion, the real sidereal period, usually to 5 or 6 decimal places in hours, rotation axis within 10 or 15 degrees, and shape within about 10%, can be found. This is called a spin/shape model. As an illustration of shape within 10%, consider the planet Saturn whose equatorial diameter is 10% greater than the polar diameter. A model of Saturn as a perfect sphere would be correct within 10%. Professional astronomers developed these programs but much of their data are now being found by amateurs. The lightcurve inversion programs are freely available, and amateur astronomers are beginning to utilize them and construct spin/shape models. [#25] However, lightcurve inversion usually finds two equally likely rotational axes at similar distances from the ecliptic but in right ascension on nearly opposite sides of the sky. The shape models for these two orientations are mirror images of each other. I illustrate for the otherwise well determined 196 Philomela. Photometry alone usually cannot resolve this ambiguity. More lightcurves would not be helpful. [#26] This diagram illustrates how asteroid satellites may be found by photometry. The upper figure is the usual rotational lightcurve for the small Hungaria type asteroid 3309 Brorfelde. The lower lightcurve is drawn to suppress the rotational variation and show narrow dips in the magnitude occuring periodically but with a different period from that of the rotational lightcurve. Total light has been reduced by a satellite in transit, shadow, or both, with a period equal to the period of revolution of the satellite. Please note that the effects of transits have been removed from the upper rotational lightcurve. [#27] This diagram illustrates a sequence of events for the binary asteroid 90 Antiope, whose physical parameters are well established. This system is unusual in that the two components are almost the same size. For most binary asteroids the satellite is much smaller than the primary. Inspection of this time sequence of events shows how light reduction by both transit and shadow occur. The total light is reduced at intervals equal to half the revolution period of the system. Asteroid satellites have also been found by adaptive optics from Mauna Kea, and by radar studies. [#28] In principle a second body could also be found unexpectedly from a densely observed occultaion. The geometry of two shadow tracks is illustrated, but to date this has not been reliably achieved. [#29] One person, himself an amateur, has played a pivotal role to enable amateur observers to dominate asteroid lightcurve work, coincidentally greatly increasing their quantity as well as quality. He is Brian D. Warner at Palmer Divide Observatory, near Colorado Springs, Colorado, a professional computer programmer. His accomplishments are many and important. (1) Brian has written sophisticated programs for both telescope and CCD control, and for image processing and lightcurve analysis. The telescope and CCD control software is called MPO Connections. It is analogous to other programs for the same purpose but especially suitable for asteroids. The lightcurve analysis software is called MPO Canopus, and has become a standard now used by nearly all amateurs and an increasing number of professionals. Both programs he has refined steadily starting about 1996 and continuing through the present. (2) He continues to provide generous assistance to an ever increasing number of observers in the use of these programs and in the analysis and interpretation of the lightcurves which they acquire. (3) Brian Warner maintains a website, http://www.minorplanet.info, for minor planet information. Here observers post their results prior to publication. Lists of asteroids with their magnitudes, opposition dates, and declinations, and for which additional lightcurves are desired, are posted. Digital versions of the Minor Planet Bulletin and of the Asteroid Lightcurve Data Base can be downloaded free of charge. The computer programs MPO Connections and MPO Canopus can be purchased on the internet with a credit card. (4) The Asteroid Lightcurve Data Base (LCDB) was originated by the veteran professional astronomer, Alan Harris. Brian Warner now does most of the day to day work of entering into the LCDB the many new and improved rotation periods as they are found mostly by amateurs. The LCDB now includes entries for more than 3000 different asteroids, stating rotation periods, amplitudes, and the reliability of these determinations. Other tables include data on sidereal periods, rotational pole positions, binary asteroids, tumbling asteroids, and references to the published literature and web sites. (5) Brian Warner is also the first author of two papers in the professional journal Icarus, the International Journal of the Solar System. These are "The Asteroid Lightcurve Data Base," and "Analysis of the Hungaria asteroid population." (6) Brian has had a major role in establishing an archive of lightcurves at the Minor Planet Center of the Smithsonian Astrophysical Observatory, which provides a permanent and secure archive for photometric measurements analogous to their archive for astrometric data. (7) Brian has an observatory at Palmer Divide, about 15 miles northeast of Colorado Springs, Colorado, with 4 telescopes all dedicated to asteroid lightcurve studies. Most people get one lightcurve each night. Brian gets lightcurves of 4 different asteroids each clear night. (8) For his many lines of research Brian has received funding by a Shoemaker NEO grant from the Planetary Society. (9) Brian was the first recipient of the Chambliss Award of the American Astronomical Society for outstanding contributions to amateur research. [#30] Photometry alone provides information on shape, but no information on size. To find the size one needs to watch an asteroid occult a star, in which the observed light drops from star plus asteroid to asteroid alone. The diagram shows the shadow of the asteroid crossing the Earth with observers located along the path. Different observers see different chords along the asteroid. Those outside the shadow see no dimming, but these negative events provide limits on the size of the asteroid. The velocity is precisely known from the orbit. The occultation chord length is this velocity multiplied by the duration of the event. [#31] Combining many chords yields a profile of the asteroid at the time of occultation. Commonly a best fitting ellipse is found, as in the case of 187 Lamberta. [#23] If a sufficient number of chords can be observed with great accuracy, a more detailed shape profile can be obtained, as for 135 Hertha. [#33] From the beginning amateurs, led by David Dunham of IOTA (International Occultation Timing Association), have provided most of the occultation observations. In the 1970's through 1990's most of the timings were visual, with tape recordings of WWV signals in the background of disappear and reappear announcements. Typical occultation times are 5 to 20 seconds. Personal errors of one to two seconds were common, and the measured sizes held considerable error. Camcorders attached to telescopes with audio input reduced timing errors. [#34] More recently webcams with times from GPS receivers have provided still greater accuracy. The more prolific observers place several of these stations across the predicted occultation paths. [#35] I illustrate measurements of target image brightness versus time for an occultation by 372 Palma. [#36] Another method of timing occultations is the CCD drift method. The telescope tracks the star until about 30 seconds before predicted occultation. Then the telescope drive is turned off, and the star images trail across the field. The times of beginning and end of dimming are measured from the scale of the CCD image. In the early days a prediction of an occultation was a chance event, and many were missed. Improvements in raw computing power enable the finding of all suitable occultations for thousands of asteroids. And improvements in the accuracy of asteroid orbits and improved star positions from Hipparcos enable prediction of center lines within a few tens of kilometers. There are now much fewer negative observations because observers located themselves outside the real occultation track. For all of the asteroids a few tens of kilometers and larger all the occultations of suitable stars are being predicted. Most of those crossing regions where many astronomers live, and which have clear weather at the time of the event, are now being observed, often with many occultation chords. [#37] I previously stated that photometry alone cannot provide the size of an asteroid, and usually cannot distinguish between two spin/shape models. Occultations observed by amateurs are now enabling professional astronomers to overcome both limitations. Given a photometric spin/shape model, the profile at any time, specifically the time of opposition, can be predicted for both possible poles. The occultation chords are matched with both models. For an occultation by 80 Sappho there is good fit to one profile and complete misfit to the other. The pole ambiguity is resolved. The pole is at longitude 194 degrees, latitude -26 degrees. [#38] In other cases, as for an occultation by 11 Parthenope, the fit to both profiles is comparably good and the pole position is not resolved. Both the number of chords and their timing accuracy have improved in recent years, but there is a need for further improvement. [#39] I now distinguish absolute and differential photometry. For variable stars one can use the same comparison stars in the field of the variable each night, and special attention can be given to finding accurate magnitudes for these stars. Asteroids move, and ordinarily different comparison stars must be used each night. To find the real magnitudes of these one must compare with standard star fields, such as the Landolt or Henden standard star fields, at different altitudes and determine the atmospheric extinction coefficients. This is a laborious process which takes time away from monitoring the asteroid itself. Furthermore it requires a photometric night in which the transparency of the atmosphere varies with altitude alone and does not change through the night. Many nights suitable for other studies are lost to absolute photometry. This was the standard method used by professional astronomers from 1950 to the 1990's. [#40] However much lightcurve work involves changes in magnitude over a single night, not the real magnitudes. One compares the asteroid magnitude with that of several stars in the same field. This is called an instrumental magnitude. The instrumental magnitudes of segments of the lightcurve obtained on separate nights are different because different sets of comparison stars are used. These can now be adjusted up and down until a good fit is obtained. [#41] In the upper diagram three nights of photometry of asteroid 26 Proserpina have already been aligned by adjustment of instrumental magnitude. A fourth session was obtained with, of course, different comparison stars. The average of their magnitudes was different from those used on previous nights. Compared with the mean the asteroid is brighter but varies as on other nghts. The instrumental magnitude for the fourth night is adjusted downward in the lower diagram until a good fit is obtained. The labor of comparing with out of field stars and computing extinction coefficients is avoided. [#42] Good differential photometry can be done with changing sky conditions, even with some cirrus clouds, because all objects in a field of arcminutes will be affected equally by this varying extinction. Many nights lost to absolute photometry can produce good differential photometry. This adjustment of differential magnitudes is fine for finding synodic rotation periods and amplitudes, and even for spin/shape modeling. Most amateur photometrists in the first decade of the 21st century used differential photometry. The limitations are that the variation over a single all night session should be considerably larger than both random and systematic errors, and the period should not be more than 2 or 3 days. Very long rotation periods cannot be found without some form of absolute photometry. [#43] Two surveys of tens of millions of stars, some as faint as magnitude 17, have greatly simplified photometry. The two micron all sky survey (2MASS) conducted at Mt. Hopkins and Cerro Tololo from 1997 to 2001 has provided infrared magnitudes over the entire sky in the J (1.25 micrometer), H (1.65 micrometer) and Ks (2.17 micrometer) infrared bands. The Carlsbad Meridian Circle Survey (CMC14) includes most of the sky between declinations -30 degrees and +50 degrees. The CMC14 survey was made in the years 1999-2005 in the Sloan r' band, centered at 623 nanometers and with half width 137 nanometers. The simple algorithm converts these to standard V magnitudes: V=0.641*(J-Ks)+r'. Photometric accuracy is typically 0.07 at magnitude 15, although only stars whic have near solar colors with J-Ks between 0.3 and 0.7 can be used reliably for asteroids. Most asteroid fields contain enough of these stars that one can select those with near solar colors and still have several comparison stars. Real magnitudes are now measured from CCD images, without the need to observe Landolt and Henden standard star fields and compute extinction coefficients. This procedure is utilized, and indeed has made possible, the routine rotation period determination for the very slowly rotating asteroids. [#44] Now an amateur organization, the AAVSO, has begun the AAVSO Photometric All-Sky Survey (APASS) to survey stars magnitudes 10 to 17 in 5 visible and near visible bands. These are Johnson B and V, and Sloan g', r', i'. When complete and published as a digital catalog this will be an order of magnitude improvement in photometric accuracy. I predict this will become the standard for asteroid CCD photometry as well as for AAVSO variable star measurements. We will have the best of both worlds, real magnitudes from each single image combined with the tolerance of differential photometry to less than ideal sky conditions. APASS will also improve the Magnitude Alert (MAP) program, as comparison with in-field stars will be enabled for whatever field is occupied by the asteroid. [#45] Awards. The American Astronomical Society (AAS) established in 2006 the Chambliss Amateur Achievement Award for achievement in astronomical research made by an amatuer astronomer. The very first Chambliss Award went to Brian Warner for the development of telescope control and photometric analysis software, continuing support of amateur astronomers in utilizing this software, and original research in asteroid lightcurve studies. In 2009 the Chambliss Award went to Robert D. Stephens for asteroid lightcurve studies. Two of the first four Chambliss awards were for asteroid lightcurve research. This shows the importance which professional astronomers, including those not specializing in solar system studies, assign to this research. [#46] Some comments on future studies. One cannot predict what new types of investigations might become available to amateurs through future technological developments. But the number of asteroids accessible with currently available equipment is large enough to keep all participants busy for many years. The principal categories are: (1) Astrometry of selected targets, especially but not entirely restricted to follow up for newly discovered and recovered Earth approachers. (2) At least provisional rotation period determinations are now available for several thousand asteroids. Future CCD photometry and lightcurve analysis will be directed increasingly toward observations at multiple oppositions to obtain shape models and precise sidereal rotation periods and two possible pole positions for these thousands of asteroids. (3) When the AAVSO Photometric All-Sky Survey (APASS) becomes available it will become the standard photometric reduction tool for both MAP and lightcurves. (4) As more data become available amateurs will increasingly use lightcurve inversion software to obtain these spins and shapes, and perhaps dominate this analysis within a few years as they already do for CCD lightcurve data acquisition. (5) It will require many decades of occultation monitoring before diminishing returns set in. Improvements in automated timing of occultation disappearances and reappearances are much desired to improve size and shape parameters and identify the correct pole position from among the two found by lightcurve inversion modeling. [#47] I conclude this presentation with some very recent images of Vesta by the Dawn spacecraft. The Jet Propulsion Laboratory has to date released only a very small number of images. The first two images [#48] show Vesta from about 100,000 kilometers, resolution already much better than the best Hubble Space Telescope images. [#49] The third image is from 41,000 kilometers. Note the parallel striations. I shall not attempt an interpretation, but you will be alerted to read the experts' interpretations when much closer images become available. On July 15 Dawn entered an orbit around Vesta, and is now obtaining images at crescent and quarter phases as well as at nearly full phase. [#50] The final images are from about 10,000 kilometers and show resolution of about one kilometer. [#51 and #52]. Finally I show Vesta to scale with seven other asteroids for which high resolution spacecraft images have been obtained [#53]. The range of sizes from Vesta (540 kilometers) down to the Earth approacher 25143 Itokawa (600) meters is perhaps much greater than many people have realized. [#54] Here is a small part of Vesta compared with the three next largest asteroids for which there have been spacecraft flybys. [#55] Here is an even smaller part of Vesta compared with the three smallest asteroids for which there have been spacecraft flybys. A collision of an object the size of 2867 Steins, about 6 kilometers, would produce a crater on Vesta comparable to the largest in the small part of the surface shown here. The text of this presentation, and all the images numbered in sequence, is in a single folder which I offer to copy to anyone who has a flash drive or portable computer. I now invite questions from the audience.