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Wu/Ji Images of Comet Hale-Bopp

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Observers: Guangjie Wu, Kaifan Ji
Location: Yunnan Observatory, China
Date: February 1996 - April 1997

Observations of Comet Hale-Bopp At Yunnan Observatory

The spring of 1996 is the first spring after the discovery of Comet Hale-Bopp. Over the winter, the comet appeared at dawn again. With a new developed CCD system attached to the one meter telescope of Yunnan Observatory we began to study Comet Hale-Bopp. A TKB 1024 CCD chip with a pixel size of 24 microns is used in this new system, it produces a field of view about 6.'5 by 6.'5 with a resolution of 0."385 per pixel.

At 6h25m30s of 28 February 1996 in Beijing time, we got the first successful CCD image. The cometary coma is very clear with a entire structure of axial symmetry. Totally, on the 6 days of February 28, February 29, March 4, March 5, March 17 and March 18, we got 56 CCD images for the comet. It includes pictures with standard V, B, R or I filters, and more number of non-filtered pictures.

Taking advantage of the GSC catalogue (NASA, 1989), we could have 35 accurate position measurements. In general, we got the inner mean error for a single star's position to be only 0.006-0.024 seconds in right ascension and 0.08-0.31 arcseconds in declination.

With SAO 160720 and SAO 188206 as standard stars, a luminosity measurement was also done. The standard V, B, R and I filters were used during 4 time periods. The magnitudes obtained with two different measurement apertures were almost the same or a little brighter than the predictive. This means that the predictive magnitudes are believable and Comet Hale-Bopp would be possible to become a "Great Comet".

All of the position measurement data is published on M.P.C. (Marsden & Williams, April 1996). These results were also published in a paper on Acta Astronomica Sinica (1997, Vol.38, No.2).

In 1997, we changed our plan, avoiding the city's light, to observe the comet at Gaomeigu of Lijiang county during the end of March to the middle of April. ,P> Lijiang is in the north-west part of Yunnan Province. The direct distance between Gaomeigu and Lijiang is about 30 km. Where the elevation is about 3200 meters high. This place was found by "Site Survey" team in recent years. Where we can often see the zodiacal light crossed with the Milkway. With a Three Sub-Aperture Differential Image Motion Monitor, it is found that the Fried's seeing parameter R0 is often about 20 cm, it means that the stellar image has a mean FWHM of 0.7 seconds.

Here we can use a 22 cm Schmidt telescope made by Shanghai Astronomical Observatory which has a field of view of about 8 degrees. A 35 cm telescope made in Japan can give a field of view of about half minute. We also fixed a Canon camera to the 35 cm telescope, it has a 75-300 mm zoom lens (or 35-70 mm zoom lens) to give a much more large field of view about 7-27 degrees.

In fact, the study of 22 cm telescope began in December of 1996. And, at the beginning of March 1997, with another similar telescope we began the 35 cm telescope study in Kunming. So that, in any camera a lot of information is obtained.

Thereafter, several pictures are selected to show you:

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Photo 1: This is the first one in our Hale-Bopp Observation Run taking on 28 February 1996 at Beijing Time 6:25:30 through 2 minutes exposure and without any filters. There are a number of GSC stars surrounding the comet.

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Photo 2: Taking on 4 March 1996 at Beijing Time. The same instrument as Photo 1 used.

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Photo 3: Taking on 27 March 1997 at Lijiang with Cannon camera. Kodak Ektapress Plus 1600 Professional Color Negative Film with over 12 minutes exposure makes the true color of the comet.

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Photo 4: Taking on 9 April 1997. The same camera but with 25 minutes exposure as Photo 3 used.

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Photo 5: Taking on 8 April 1997 with the same Canon camera but a 35-70 mm zoom lens mounted. Since we have no Fish-Eye lens, in the 3 minutes exposure centered at 21:11 of Beijing Time you can only see the Pleiades (M45 open cluster) was deeply in the zodiacal light, and the comet on the right side.

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Photo 6: Taking on 8 April 1997 with the 22 cm telescope. Kodak 400 Black & White Film was used. Blue is a false background color. The plasma tail was divided into over ten streamers, each of which corresponds to a period of enhanced activity.

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Photo 7: Taking on 9 April 1997. Same instrument as Photo 6 used.

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Photo 8: Taking on 10 April 1997. Same instrument as Photo 6 used. A disconnect event can be seen in the gas tail.

Prof. Guangjie, Wu & Dr. Kaifan. Ji
Comet Hale-Bopp Group of Yunnan Observatory, July 1997
ccd@public.km.yn.cn


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