The Astro-Tech AT72EDII refractor, with it's 430 mm focal length and meager 72mm (2.8") aperture, is not an ideal planetary telescope. In the not-so-dark skies of urban Santa Fe it is better suited to photographing or observing star clusters or the Moon and Sun. However, it is fun to see what can be done with it. So far it has picked up two moons of Uranus (Titania and Oberon) and a dim and distant moon of Jupiter (Himalia), none of which I had seen before.
Last night the scope was turned to Saturn, Neptune, and the dwarf-planet Ceres.
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| The current locations of Ceres, Neptune, and Saturn. (credit: SkySafariAstronomy.com) |
Five moons of Saturn were visible in a 20-sec exposure:
Four of the moons, Titan, Rhea, Dione, and Tethys are in a line with Saturn's ring plane. The rings are hidden in the glare of the overexposed planet and are currently nearly edge-on. A fifth moon, Iapetus, sits just above Saturn accompanied by a background field star.
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| Credit: SkySafariAstronomy.com |
Neptune is a more difficult target. Last night, its largest moon Triton was separated by only 11 arcseconds from the planet. It appears to be just-barely visible in a 5-sec exposure:
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| Neptune and Triton. 3x enlargement. |
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| Credit: SkySafariAstronomy.com |
At magnitude 13.8, Triton requires a fairly large telescope to be observed visually. It is about 77% the diameter of our Moon, and is larger than the dwarf-planet Pluto.
Ceres is the closest dwarf planet to Earth, orbiting in the main asteroid belt between Mars and Jupiter. It is currently at magnitude 9, about the same as Saturn's moon Titan.
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| Ceres (circled). 1-deg FOV (vertical). |
The sky brightness last night was sqml=19.68, which is an improvement from the previous few days.
Some more star-cluster pictures:
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| M34 in Perseus. 1-deg FOV. 30-sec exposure. |
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| NGC 1582 in Perseus. 20-sec exposure. |
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| M37 in Auriga. 25-sec exposure. |
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