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D. West (Mulvane, KS), R. Lorenz (LPL, University of Arizona)
We report on observations made with amateur equipment (20-25cm telescopes) of Titan, Uranus and Neptune. Simple slitless spectrographs constructed from off-the-shelf CCD cameras and diffraction gratings allow useful spectra of Uranus with exposures of less than one minute and resolutions of a few nm. Neptune is a more challenging target. being fainter ; Titan, while similarly faint, has the additional difficulty of substantial scattered light from Saturn. Nonetheless, with some care, good spectra can be obtained. Flux and wavelength calibration is performed by observing known stars such as Vega.
Our Uranus spectra compare well with literature results (e.g. Neff et al., 1984) with some evidence of reduced infrared brightness, consistent with HST observations of seasonal variability (Karkoschka, 2001). Analysis of Neptune and Titan spectra is presently ongoing.
Additionally, Ic-band photometry of Titan appears to show longitudinal variation, albeit with higher-than-expected amplitude, and substantial scatter. Whether amateur capabilities towards longer near-IR wavelengths permit detection of cloud activity on Titan remains to be seen.
These observations underscore the capabilities of modern equipment to make useful contributions in planetary science in monitoring long- and short-term changes in the atmospheres of the outer planet atmospheres. We urge other amateurs and educators to contribute observations in this area.
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The author(s) of this abstract have provided an email address for comments about the abstract: rlorenz@lpl.arizona.edu