C/2004 F4 (Bradfield)

Copyright © 2004 by Michael Jäger and Gerald Rhemann (Stixendorf, Niederösterreich, Austria) Michael Jäger and Gerald Rhemann obtained this image of comet Bradfield on 2004 April 28.12. This is a 10-minute exposure obtained with a 20-cm Schmidt Camera. Discovery A new comet was announced on April 12. Found by William A. Bradfield of Australia, it is the 18th comet found by this observer. His first was in 1972 and he has found comets in every decade since. Bradfield found this comet near the horizon in twilight, while searching for sungrazing comets, on March 23.43. The magnitude was then given as 8. After a further observation on the March 24.42, he officially announced the discovery. Unfortunately, neither Bradfield or any other observer obtained additional observations in the immediate days that followed. Bradfield himself recovered this comet on April 8.4 and R. H. McNaught (Siding Spring Observatory, Australia) found the comet on April 9.37 and estimated the magnitude as 5. Terry Lovejoy (Australia) saw the comet on April 11 and 12. He has provided the first precise positions and gave the magnitude as 3.3 on the 12th. McNaught also visually saw the comet on the 12th and described it as stellar looking with a tail possibly 2° long. Lovejoy was able to photograph the comet again on April 13.35, but it was near the limit of detectability in the bright twilight and no position could be measured. Historical Highlights The first orbit was finally published on IAU Circular 8319 (2004 April 12). It was a parabolic orbit based on two precise positions and several rough positions. Green said this "very preliminary" orbit indicated a perihelion date of 2004 April 17.12 and a perihelion distance of 0.169 AU. The Solar and Heliospheric Observatory (SOHO) obtained a nice series of images of this comet during the period of April 15 to 20, as well as observations of the tail well into April 21. This helped firm up the orbital calculations. The first observation of the comet in the morning sky was made by Michael Jäger and Gerald Rhemann, who observed from Stixendorf, Austria on April 22.12. Bright twilight was present and the comet was at a low altitude. No magnitude was estimated, but several German amateur astronomers who failed to locate the comet estimated that it must have been fainter than magnitude 2. Alan Hale (Cloudcroft, New Mexico) spotted the comet on April 22.48 with a 20-cm reflector. He said that in bright twilight the central condensation was visible, as well as a hint of material extending toward the west-northwest. He said the condensation was slightly brighter than the star 84 Piscis, causing him to estimate the comet's magnitude as 4.5. J. Shanklin (England) spotted the comet on April 23.14 while using 20x80 binoculars. He estimated the magnitude as 2.6. The comet was widely observed and widely photographed in the morning sky during the remainder of April, as it faded to magnitude 5.8. The comet was accompanied by a long tail, with visual observers noting a length of up to 10° on April 27 and photographers revealing over 20° around the same date. Additional Images Copyright © 2004 by Terry Lovejoy (Queensland, Australia) Image of C/2004 F4 on 2004 April 12.34 when 14° from the sun as it headed toward its April 17 perihelion passage. Lovejoy used a Canon 300D camera with a 100mm lens set at 400ASA. This is a combination of seven unguided 3.2-second exposures. Lovejoy cropped this image to a width of 3°. Copyright © 2004 by SOHO This image was created by the webmaster using images obtained by the Solar & Heliospheric Observatory (SOHO) during the period of 2004 April 15 to 18. The dark blue disk near the top is a component of SOHO that is blocking out the sun, while the white circle within it represents the outline of the sun. Copyright © 2004 by Michael Jäger and Gerald Rhemann (Stixendorf, Niederösterreich, Austria) M. Jäger and G. Rhemann obtained this image of comet Bradfield on 2004 April 22.12. It was then in bright twilight. They were using a Leica 180mm Apo-Tele f/3.3 with a Starlight SXV-H9 CCD camera and a red filter. Six 4-second exposures were combined to achieve this image. At the time this image was taken the comet was 14° above the horizon and about 70 minutes prior to sunrise. Copyright © 2004 by Katsuhiro Mouri (Nagoya, Japan) Katsuhiro Mouri, planetarium curator of the Nagoya City Science Museum, obtained this image of comet Bradfield on 2004 April 25. This was a 30-second exposure obtained with a digital camera set at ISO 100, using a 200mm f2.8 lens. Copyright © 2004 by Anthony Arrigo (Park City, Utah) Anthony Arrigo obtained this image of comet Bradfield on 2004 April 27. This was a composite of nine 30-second exposures obtained with a Sony DSC-F717 digital camera at f/2.4. The camera was riding piggyback on a 120mm refractor. Copyright © 2004 by Rolando Ligustri (Latisana, Italy) Rolando Ligustri obtained this image of comet Bradfield on 2004 April 27. This was two 60-second exposures obtained with a SXHV9 CCD camera and a 24mm f/2.8 lens. M31 is at the top of the image. Copyright © 2004 by Wally Pacholka / AstroPics.com (Joshua Tree National Park, California) Wally Pacholka obtained this image of comet Bradfield on 2004 April 25.49. It was obtained in Joshua Tree National Park, a spot Pacholka has obtained many great comet photographs from in the past. This image is also special because the Andromeda Galaxy, M31, is also visible in the upper part of the image, just left of center. Pacholka used a 35mm camera, with a 50mm lens on a tripod for this image. Bradfield's tail extends 20°. Copyright © 2004 by Gerald Rhemann and Michael Jäger (Stixendorf, Niederösterreich, Austria) Gerald Rhemann and Michael Jäger obtained this image of comet Bradfield on 2004 April 28.09. This is a 2-minute exposure obtained with a Leica 180mm Apo-Tele f/3.3 with a Starlight SXV-H9 CCD camera. Copyright © 2004 by Rolando Ligustri (Talmassons, Italy) Rolando Ligustri obtained this image of comet Bradfield on 2004 April 28.12. It is a composite of seven 60-second exposures obtained with a 35-cm reflector and an ST9e CCD camera. The scale is 2.35 arc seconds per pixel. Copyright © 2004 by Len Benschop (Oshawa, Ontario, Canada) Len Benschop obtained this image of comet Bradfield on 2004 April 28.41. It is a composite of twelve 30-second exposures acquired by a Celestron C8 Ultima and a Starlight Xpress MX7C CCD camera. Copyright © 2004 by Bill Hampton (Landers, California, USA) Bill Hampton made this pencil drawing of the comet on April 30.48. It is a composite based on his view through 10x binoculars. He inverted the image to better represent the appearance. Copyright © 2004 by Dean Jacobsen (Vista, California, USA) Dean Jacobsen obtained this image of comet Bradfield on May 2.48. It is a 90-second obtained using an SBIG ST-2000XM CCD camera through a Nikon 50 mm lens. (The image was flipped horizontally by the web master to better represent the comet's true orientation.) cometography.com