Me and My Baby View the Transit of Mercury
(with apologies and thanks to Lee Smith for the title, Me and My Baby View the Eclipse.)
(Near mid-transit during an interval of good seeing.)
The four drawings below are fair representations of the beginning of the
transit of Mercury on November 15, 1999, as observed in hydrogen-alpha
light prior to contact I.
The first drawing represents my first glimpse of the planet already almost
entirely silhouetted against the chromosphere. I had noticed it perhaps 30
seconds earlier as a rounded, enduring dark "shadow" within the seeing-distorted,
glowing crimson haze. (4:08 PM, EST.)
The second drawing depicts Mercury during its crossing of the chromosphere.
The bright halo, which was often striking through the eyepiece, is surely a
contrast effect. The planet seemed to darken as it "penetrated" deeper. This
is another contrast effect, of course, as the same black ball moved over
brighter and brighter gases. (4:09:30)
The seeing was horrible during much of ingress. Even when the limb of the Sun
was badly distorted, the enduring dark swatch seemed strikingly circular. I
suppose this is due to the eye's retaining constant detail even in the face of
rapidly shifting noise. Planetary observers depend on this, of course, but
I've never seen the phenomenon so vividly displayed. (4:12)
Finally, during periods of good seeing, this is how the planet looked. At this
point, I supposed photospheric contact was imminent and I changed to a white-light
filter. It was another 3-4 minutes before I glimpsed the notch made by the planet in
the white-light solar image. In white light, the seeing was much worse. Perhaps
the more turbulent, more confused image was owing to differential refraction of
light of many wavelengths, or perhaps the white-light image was degraded because
I was using the full 5-inch aperture of the telescope rather than the masked 77mm
aperture used for hydrogen-alpha viewing.
Observed through an AstroPhysics 5-inch refractor, masked to 77mm, with a
Lumicon 1.5A h-a filter, a 2x barlow and 26mm Meade and 12mm Nagler
eyepieces. The effective f-ratio is about 1:27 which is just about the
minimum for decent monochromator performance. Amy and I were watching
(with passersby and other visitors) from the sunny shores of Lake Rhodhiss
just north of Rutherford College, North Carolina. I prepared the drawings
in Adobe Photoshop 5.0.2 from field sketches and notes.
Email:DavidCortner@pobox.com.
Take me home, Mr. Wizard!