Asteroid Detection with the Centurion 18 from Aguila, Arizona
April 6, 2000

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On the night of April 6, 2000, Dr. Carol Neese and and Gil Esquerdo of the Planetary Science Institute (PSI) visited Jim Riffle in Aguila, Arizona to test the suitability of the Centurion 18 as an asteroid and comet search instrument. This page summarizes the results of that test.

The final analysis of the data reveal an effective limiting magnitude of 20.0 in 90 second exposures (all images taken for the test had the same exposure time). This is using a SBIG ST-8, non-antiblooming protection camera. While not as sensitive as the same type camera with the new enahnced or "E" chip, it is similar in sensitivity to an "E" camera that does have antiblooming protection. In short, the structures in the CCD chip that prevent the unsightly overflow streaks seen on bright stars also reduce the sensitivity of the CCD by about 50%. As the antiblooming gates compromize the scientific usefulness of the data, we opt to use a CCD camera without them.

The survey project we have developed will use computerized moving object detection software to look for asteroids and comets. For this test though, all images were visually inspected for moving objects. The great quantity of asteroids visible demonstrates that anyone dedicated enough can discover many new asteroids and potentially comets with the Centurion 18, a CCD camera and some time.

Figure 1.
Figure 1 (262Kb) is an animated GIF image of the 34 asteroid and comet detections made with the Centurion 18. The first 14 objects were specifically targeted objects while the remainder (excluding 2000 EE104) were the result of four random fields selected along the ecliptic. 13 known asteroids were detected in these fields, as well as six previously unknown asteroids.

The magnitudes range from 16.0 for 2000 EE104 and the main belt asteroids (7768) and 2000 EK95 down to 19.9 for 2000 FP2 and 2000 FG4. The duration between first and last images in the sequence is about 45 minutes for all the objects except 2000 EE104 where start to finish is about 7 minutes. At the time, 2000 EE104 was very close to the Earth and as a result was very bright and moving very fast across the sky (about 15 degrees per day).

Note that these images have been passed through a software filter that reduces some of the background noise, but as a result, smooths out some of the detail. Each tile is about 90 arcseconds on a side, with the exception of the 2000 EE104 image which is 220 arcseconds wide.

Figure 2.
Figure 2 (4Kb) is an illustration showing the direction and extent of motion of the asteroids in the above animation.

Figure 3.
Figure 3 (11Kb) is a key providing the names of each asteroid or comet detected. When we were unable to link a detected object with a known asteroid or comet, it has been labeled NEW. These represent previously unknown asteroids, and in essence constitute discoveries. In this case, six new asteroids were found in searching just FOUR fields totaling about 0.9 square degrees of sky. This is an indication of the ease with which the Centurion 18 can be used to discover new asteroids.

Figure 4.
Figure 4 (478Kb) is an animated GIF image of part of one of the four ecliptic search fields. Three large (bright) main belt asteroids can be seen moving in this image. They are (clockwise from upper right) 1999 YP12, 2000 EK95 and 7768 (1991 SX1).

Figure 5.
Figure 5 (96Kb) shows the Landolt Standard Area 104. These are regions of the sky where the brightnes of the stars in the field have been measured very carefully and are used to calibrate the response of an astronomical instrument. It was used to find the true limiting magnitude of the Centurion 18 when used in an asteroid search mode.

Regardless of the use, often times, a randomly imaged piece of sky reveals many interesting objects. Standard Area 104 contains the galaxies NGC 4642 (lower right) and NGC 4653 (upper left), as well as many smaller, anonymous galaxies. This image is the sum of four, 90 second exposures taken of the area.

Figre 6.
Figure 6 (403Kb) is a sum of eight, 90 second exposures of a small region near Landolt Standard Area 104. We visited this region a couple of times during the night to image different portions of the standard area. There was some overlap between the two different pointings. To truly demonstrate how impressive we found the Centurion 18 to be, we summed the eight images that overlapped.

The faintest objects in this image are about magnitude 21.2. Note the large number of very faint galaxies visible just above the background level. The bright, diagonal stripe across the top is the trail of a geostationary communications satellite that passed through the field while one of the images was being taken. A very dedicated observer who chose to image to this depth could possibly begin discovering large Kuiper Belt objects if enough time elapsed between images to allow these very slow moving objects to make their motion perceptible.

The scientific possibilities with the Centurion 18 are remarkable, and it is up to the imagination of the user to determine what they want to do.

PSI would like to thank Jim Riffle for having us out to see the Centurion in action and perform out tests. We look forward to being able to use one of our own for our asteroid and comet search project.

If you are interested in pursuing either asteroid and comet astrometry (the precise measurement of these objects position in the sky) or the discovery of these objects, visit the Guide to Minor Body Astrometry page provided at the International Astronomical Union's Minor Planet Center web site. The IAU is the international clearing house for all asteoid, comet, nova and supernova discoveries.

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