Observing report for 10 March 1997




Comet Hale-Bopp


Here's another Hale-Bopp observations from Kitt Peak National Observatory west of Tuscon, including an attempt at an ASCII drawing of the detail near the nucleus.

It was clear again this morning and again I squeezed in some naked-eye and binocular observations of Hale-Bopp whie taking stellar spectra for my thesis. Naked-eye limiting magnitude again was +6.7 near Polaris, and again I didn't hae a chance to get total dark-adaptation. As a check, I was able to see the United States part of the North America Nebular naked-eye, but was not able to get the Mexico part except with binoculars. The comet appeared essentially the same as yesterday morning and I could trace out the plasma tail 14 degrees naked-eye and the dust tail about 7 degrees. The dust tail is positioned closest to Tucson light pollution which is of similar color, so I'm probably losing some contrast. I found a low wall on which to steady my 7x50s to get a more detailed view of the coma area. I was able to see the slight "hockey stick" shape of the combination of the nucleus and the initial bright part of the dust tail, i.e. the tail looks like it's taking an abrupt left turn after coming off the nucleus.

I also took some spectra of the comet and got an excellent close-up view of the nucleus area. The telescope is a 0.9-meter f/31 unobstructed design. To enter the comet up on the slit, I looked through the 4"-barrel eyepiece which I determined gives about a 6-arcminute field of view (at presumably very high magnification). In the quick look here, I could see three concentric arcs within about an arcminute of the psuedo-nucleus. Back in the control room, I could study the comet at a more leisurely pace on the auto- guider while integrating (albiet, it's not designed to give high quality viewing). Here's a crude ASCII sketch of the nuclear area, almost to scale (you'll need to view this with a mono-spaced font):

             (      _-
            (      (
           (      (
          (      (    UU
         (      (    (UU
         (     (    (  X
               (    (

      north-northeast ------->

'(', '-', and '_' are the arcs, which should be little more curved than it possible to depict here. The X marks the pseudo-nucleus which was several arcseconds across and didn't seem to have a sharp boundary (seeing was about 1.5-arcseconds), and 'U' represents an apparent jet. Past the jet there was still a faint glow. The center of the inner arc was about 5 or 6 arcseconds from the psuedo- nucleus. The arcs were progressively fainter farther from the nucleus. I didn't stop taking comet spectra until about 20 minutes before sunrise, but by this point sky emission lines were starting to show up in the spectra

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