This is a Composite of 50 -15 second exposures taken with an Apogee AP-7 CCD camera. The first exposure was taken 04-24-97 at 01:12:47 UT. The images were enhanced to show the jets from the nucleus.

We superimposed 30 exposures and then made a contrast enhancement with 3 different filtering methods, each showing different structures in the coma. They add the following comments: From other observers is reported, that the various arcs are ejected by the same active spot (IAUC 6583, IAUC 6587) and the amateur astronomer Bill Matthews thinks, that the shells are in real a spiral looked from the side. F. Manzini and his colleagues (Instituto di Fisica dello Spazio Inter-planetario del CNR di Frascati, Italy) remark that both bursts, which they observed on Sep. 11, 1996 and Feb. 9, 1997, evolved from a single jet, and that this speaks against the hypothesis by Zdenek Sekanina about the origin of multiple jets on Hale-Bopp.However, when looking at our picture we think that two spirals can be seen, one large outer one that creates the large 'shell structure', and a smaller one that is reponsible for the smaller one. This can be achieved by two jets with different radial velocities. Thus, we think that this supports the model of Sekanina, which uses multiple jets.

This is a 1 second exposure of Hale-Bopp's coma.

Change in the inner coma : new helicoidal jet

Authors: Francois Colas
Location: Pic de Midi Observatory (France)
Optics: 105 cm telescope.

The images were taken with a Gunn 6 filter on April 14th and April 15th. They show rapid change in the inner coma. The more interesting new evolution is the apparition a an helicoidal dust jet even at the opposite side of the sun.

Author: David McDavid
Location: Limber Observatory, Pipe Creek, Texas
Optics: 0.4 m telescope.

Comet C/1995 O1 (Hale-Bopp) at 02:57 UT, April 14, 1997. North is up, east is left, and the field of view is about 4 arcmin square. The image on the left is an ordinary intensity image. The image on the right is a polarization image (brightness proportional to the degree of linear polarization). These were derived from three pairs of 3.5 second exposures through polarizing filters oriented at 45, 90, and 135 degrees, together with a Cousins R filter, using a Photometrics CCD camera (Thomson 512 chip) at the f/12 Cassegrain focus of the 0.4 m telescope at Limber Observatory.
The "arc" or "hood" structures in the inner coma are strongly polarized, from about 20% in the innermost arc to about 10% in the outer ones. This suggests that they are dense concentrations of dust that produce polarization by the scattering of sunlight.

New daytime observations

Authors: Francois Colas
Location: Pic de Midi Observatory (France)
Optics: 105 cm telescope.

We still continue to observe comet Hale Bopp during daytime at Pic du Midi. This is the sum of 50 images of 0.4 second. Our goal is to observe a few "full rotations" of the comet to better understand the complex nucleus dynamic.

28 x 20 second exposures of Hale Bopp, taken through a blue filter have been combined and processed by subtracting a 5 by 5 pixel masked version from 105% of the original image.

High resolution shell structure

Authors: Jean Lecacheux, Francois Colas
Location: Pic de Midi Observatory (France)
Optics: 105 cm telescope.

We processed the sum of 30 individual images taken with a red broad-band filter (670-820 nm ). The first image is the result of a radial gradient, for the second we subtracted a radial profile to reduce the dynamic range between the inner and outer coma.

The image was obtained processing the sum of 25 0.3 sec images.

This false-color image was obtained by the Class of Astronomy (K12), with a little help, of course. The original 0.6 second exposure was filtered with LAIA, a program developed and distributed by the team GEA, at Barcelona. Three different channels were then summed with Paint Shop Pro:

• red channel, laplace filter, sigma 2 and radius 9,
• green channel, random contour filter #1 3 x 3
,
• blue channel, mean contour filter (12, 10 and -10).

The image is the sum of 25 red filter 0.3 sec images.

Image 2 hours after perihelion showing a double shell system

Authors: Jean Lecacheux, Francois Colas
Location: Pic de Midi Observatory (France)
Optics: 105 cm telescope.

This image was taken on April 1st, at 5h03 UT just after comet perihelion (April 1st, 3H18 UT). This image is representative of our extensive comet survey using Gunn 6 filter and the 105 cm telescope. The comet is now difficult to observe in the morning sky, we can point the telescope only 1 hour before sunrise, the comet is at only 10 degrees of elevation.

The image was processed with a radial gradient to enhance the shell structure. The dust shells visible since the end of january are now showing a double structure. Each "wave system" have the same interval but not the same curvature. This double structure have to be study in relation with the two jets now clearly visible, close to the nucleus