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2017 Jan 15 15:49 UTC
Source file:
1997comets.txt
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C/1995 O1 (Hale-Bopp)The discovery of this comet was announced on TA e-circular E975. It put on a remarkable show in early 1997 but it is now unobservable from British latitudes. The comet reached its highest altitude in the western evening sky in early April 1997, just at perihelion. The 3D orbit diagram shows that Hale-Bopp is in a highly inclined orbit.David Strange captured this CCD image of the comet at 2315 on 1995 July 26. This was taken from the UK with the comet barely 7 degrees above the horizon. Throughout 1995 and early 1996 the comet brightened and moved slowly north. By the summer of 1996 it was well placed for observation from the UK. Martin Mobberley obtained this image of the comet on 1996 June 13 at 0045. He used a 0.49m Newtonian and an 80s exposure with an SX camera. Two days later on 1996 June 15 Nick James obtained an image using his 0.30m Newtonian. Both images show a distinctly asymmetrical coma with an extension to the north. This extension is not the tail (that should point south) but can only be a massive sunward-pointing fountain of material. Grant Privett and P. Boyce obtained this image on 1996 June 21 using the 1-m JKT at La Palma. This is a 30s exposure at 03:18:53 using an R-band filter. The pixel size is 0.3 arcsec but the seeing was poor and the image was obtained through thin cloud. The asymmetry of the coma is well seen. By 1996 July the comet was showing some very unusual activity. This false colour image taken on 1996 July 13 shows that the coma has a very strange shape. The image was obtained by Nick James using a 0.3m Newtonian and an SX camera. David Strange suspects a jet in the central region of the coma in this processed image taken on 1996 July 14. Also on July 14 Martin Mobberley took this relatively wide-field image of the comet using a 0.16m, f/3.3 Takahashi and an SXL8 CCD. By 1996 July 24 the westward pointing bright jet was quite prominent. This image was obtained by Denis Buczynski using the 53cm reflector at Conder Brow. The jets had developed dramatically by 1996 August 4. This image was obtained at 2122 by Nick James. It has been radially enhanced to show jet detail in the inner coma. An hour later at 2233 David Strange obtained this image which has been processed using a conventional high-pass filter. He used his 0.50m, f/4 telescope and an SX camera. North is at the top in both images. By August 18 when Denis Buczynski obtained this image the jets had developed even further. The image was obtained with a 0.53m telescope and an SX camera. At least six jets are visible in this image of 1996 September 5 taken by Martin Mobberley with his 0.49m Newtonian. The most prominent jet to the NE is clearly visible even in small telescopes. The magnitude of Hale-Bopp did not brighten as predicted in September leading some to comment that the comet was a spent force. Despite this the activity was maintained as shown in this Terry Platt's image of 1996 October 5. Terry comments "I get the impression that Hale-Bopp is beginning to burst into life as a "real" comet, with a distinct tail and lots of jet activity... I have taken many images of it since May, and those from last night (the 5th) show the most activity yet. [This is] an SXL8 image taken with the 330mm F4.3 camera at 18:57 UT and an exposure of 160 seconds... North is up." The jets are still visible in this image of 1996 October 12 taken by Martin Mobberley. This is a fragment of the original image which was taken using an SXL8 camera on a 0.16m, f/3.3 telescope. The exposure lasted from 1850 to 1900 and the field is approximately 35 x 25 arcmin with north at the top. The comet was becoming more difficult to observe as it sank into the early evening twilight in 1996 November. The jets were as active as ever when Denis Buczynski obtained this image on 1996 November 10 at 18:36. At least three jets are visible to the East and One to the West in this 180s exposure obtained with a Celestron Comet Catcher and an SX CCD. A further image from Denis taken on 1996 December 13 shows considerable activity. Those with good western and eastern horizons managed to follow Hale-Bopp right through conjunction. These images show the development of the comet between 1996 November 25 and 1996 December 28. Both are 20s exposures by David Strange using his 0.50m, f/4 Newtonian with an SX camera. The latter exposure was taken in strong twilight. In January the comet had risen high enough in the eastern morning sky to be a good object. This image of 1997 January 16 was obtained by Nick James using a 0.30m, f/5.25 reflector. The image is a composite of twenty ten second exposures. The short exposures were used to avoid saturation of the inner coma. An unsharp mask was then made using a radius 20 statistical median filter. The mask was scaled by 0.9 and subtracted from the original image. Finally a low pass Gaussian filter was applied to reduce noise and the image was colour coded. The field size is 12 x 8 arcmin which corresponds to 1.2 x 0.8 million km at the 2.3 a.u. range. Further images using the same processing techniques show gradual changes to the coma structure and the development of "waves" in the inner coma. A wider field image of the comet, also obtained on 1997 February 3 shows an impressive tail. Martin Mobberley used a 5 minute exposure from 0531-0536 with a Takahashi E-160 Astrograph (160mm f/3.3 = 530mm f.l.) The field of view is = 50 x 50 arcmin. An SXL8 CCD was used which had a pixel size of 6". The colours in the tail are shown well in this image by Terry Platt obtained at 0425UT on 1997 March 6. He used a 200mm f/4 lens, an SX colour camera and added two 40 second exposures. This beautiful picture of Comet Hale-Bopp and an aurora was taken on 1997 March 8 at 01:00 from Covesea, Morayshire, Scotland. Tim Schroder used a 25 second exposure with a 50mm f1.7 lens on Kodak Ektar 1000. A few hours later Denis Buczynski obtained a much larger scale image using a 27" focus f/5 Zeiss triplet lens on a 5"x4" T-Max 400 negative. The exposure was 30 minutes between 0412 and 0442 on 1997 March 8. The contrasting colours of the dust and gas tails are well shown in colour photographs. Martin Mobberley took this photograph using Fuji SG-800 film at the focus of a Takahashi E-180 (530mm FL, f/3.3). The exposure was 12 minutes from 0354 to 0406 on 1997 March 13 and the field of view is approximately 2 x 3 degrees. Nick James obtained a rather wider field photograph on the same film a day later. He used a 2 minute exposure with a 135mm telephoto lens on 1996 March 14 starting at 0445. The field of view of this image is approximately 10 x 8 degrees. The comet was by now so bright that it was visible in twilight. Nick James took this frame at 0457 on 1997 March 14 using a 55mm, f/2 lens, Super-G800 film and a 30s exposure. At a much larger scale the inner coma shows multiple rays and shells in this image of 1997 March 18. Martin Mobberley has processed this image of 1997 March 19 to show as nearly as possible the visual impression through a telescope. This frame consists of four 2 second exposures using an SXL8 and a 0.36m f/5 Newtonian. The exposures started at: 1937 UT, 1938 UT, 1939 UT and 1940 UT. Terry Platt has been taking exposures of the inner coma using a colour SX camera with the aim of making a movie of the nucleus' rotation. This 10K MPEG movie consists of five frames obtained between 1903UT and 2838UT on 1997 March 21. Each frame was a ten second exposure using an f/20 Tri-Shiefspiegler. Since the movie is only five frames long it is best viewed with your MPEG viewer set to a slow frame rate and in looping or repeat mode. A more complete movie taken between 1900 on 1997 March 28 and 0450 on March 29 shows a complete rotation of the nucleus. Further images of the comet:
Changes to he structure of the inner coma over the early part of 1997 can be seen in this slide. C/1997 D1 (Mueller)CCD image taken on 1997 May 11.C/1997 J1 (Mueller)CCD image taken on 1997 May 30.C/1997 J2 (Meunier-Dupouy)CCD images taken on 1997 May 29 and 1997 May 30.C/1997 T1 (Utsunomiya)CCD image taken by Denis Buczynski on 1997 October 8 using the 0.33-m f/3 CBAT and an SXL8 CCD. Martin Mobberley obtained an image using a colour SX camera on 1997 October 21. This is the result of eight stacked one minute exposures taken between 1914 and 1924 using a 0.49-m, f/4.5 Newtonian. The tail is nicely visible in this exposure obtained on 1997 October 24 by Nick James. This is the result of stacking forty 40s exposures centroided on the comet. |
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