David Schleicher: Comet Hale-Bopp

March11, 5am
205mm, f/4, 8 minutes
Fuji: Super G 800 Plus
(w/out moonlight)
March10, 8pm
205mm, f/4, 8 minutes
Fuji: Super G 800 Plus
(w/ moon light)
March 6, 6am
Missile test from White Sands, New Mexico
Photographed from Flagstaff, Arizona
March 10
Photograph by Henry L. Giclas
with the historic Pluto telescope
(the telescope that discovered Pluto)

This image of Comet Hale-Bopp was obtained with the Hall 42-inch (1.1-m) telescope at Lowell Observatory on 1997 Mar 6 by Sue Lederer (U. Florida) and David Schleicher (Lowell Obs.), and processed by Tony Farnham (Lowell Obs.). A red, narrowband filter was used to isolate light reflected by dust grains in the comet's coma. Pseudo-colors have been applied, where dark red represents low intensity, then bright red, and finally yellow/white the highest intensity. The first figure is "raw" (only bias subtracted and flat-fielded) and shows the comet centered, with a very bright core, and with the dust dropping off in brightness with distance from the center. The second figure shows the same image after processing to remove the gross fall-off in brightness, allowing detailed dust structures to become visible. [A 1/rho canonical dust fall-off was ratioed out, where 1/rho would be expected for a simple, static comet for which dust is flowing radially outward uniformly in all directions.] The extreme asymmetries in the coma are clearly evident in both views, with the upper-right quadrant being the brightest with the most material and the lower-right being the faintest. The 2nd figure better shows brightness variations within the stuctures of the upper-right quadrant, revealing a series of dust arcs, due to short-term changes in production modulated by the rotating nucleus (i.e., active regions on the surface turn "on" and "off" as they rotate into and out of the sunlight). The 3rd figure shows the image processed using an unsharped mask technique, which emphasizes strong changes in brightness. This method makes the full extent of each arc more apparent.

Other notes:
The heliocentric distance of the comet was 1.02 AU. The geocentric distance was 1.41 AU. Solar phase angle is 46 deg (the sun is between us and H-B). The position angle of the sun is 159 deg (North is at the bottom and East is to the left, so the sun is towards the upper-left). The image size (side-to-side) is 3.8 arcminutes or about 230,000 km.

[Comet research overview | Lowell research]