Is it a conspiracy that no major observatories have photographed Hale-Bopp since October 1996?

Everyone loves a good conspiracy theory, but you won't find evidence for one here. Hubble Space Telescope first observed Hale-Bopp on 27 August 1997, which is when the comet emerged from the HST solar exclusion zone. (HST could not observe Hale-Bopp earlier in 1997 because the angle between the sun and the comet was smaller than 50 degrees and pointing HST that close to the sun could damage the telescope and/or its instruments.).

Another problem is that comets are so big that large telescopes are useless for studying them. In the February 1997 issue of Astronomy there is a photo taken with the world's largest CCD camera on the Canada-France-Hawaii Telescope on Mauna Kea which is a 3.5 meter telescope.

The above photo, taken with the 2.2 meter telescope at the University of Hawaii observatory at Mauna Kea on February 17, 1997 shows complex jets after much of the brightness of the diffuse coma has been suppressed. The field is 2.5 arcminutes wide, and at the distance of the comet at that time, this equals a linear scale of 85,000 kilometers edge-to-edge. This is why using big telescopes is mostly counter productive to studying comets 'up close'. You completely 'resolve away' all of the other details. Compare this with a photo taken on March 22, 1997 at perihelion...closest approach to the Sun...using a Nikon N90s camera with a 200mm lens at F2.8!

For more pictures like these, visit the U.Hawaii IRTF Observatory Hale-Bopp photo archive.

Copyright 1997 Dr. Sten Odenwald

Return to Ask the Astronomer.