After Tom’s extraordinary capture of the twins of fear and dread, I tried for the “easier” moon, Deimos on 9th April with the Mewlon 180 and ASI120MM CCD camera and succeeded in recording its presence in one of the diffraction spikes of the Mewlon’s 3 vane secondary spider.
Asaph Hall discovered the two moons of Mars in 1877. Deimos on the night of the 12th August and Phobos six nights after. The telescope used for the discovery was a 26-inch (66 cm) refractor. Hall named the moons for the mythological sons of Ares, the Greek counterpart of the Roman god, Mars. Phobos (fear) and Deimos (dread).
Mars' moons are among the smallest in the solar system. Phobos is a bit larger than Deimos, and orbits only 6,000 km (3,700 miles) above the Martian surface. No known moon orbits closer to its planet. It whips around Mars three times a day, while the more distant Deimos takes 30 hours for each orbit. Phobos is gradually spiralling inward, drawing about 1.8 m closer to the planet each century. Within 50 million years, it will either crash into Mars or break up and form a ring around the planet.
Like Earth's Moon, Phobos and Deimos always present the same face to their planet. Both are lumpy, heavily-cratered and covered in dust and loose rocks. They are among the darker objects in the solar system. The moons appear to be made of carbon-rich rock mixed with ice and may be captured asteroids.
Phobos has only 1/1000th as much gravitational pull as Earth. A 150-pound (68 kg) person would weigh two ounces (68 grams) there.
I’ve attached a stretched raw frame, a composite to show the planetary disc correctly exposed from the same session and a simulated view from Starry Night Pro 6.
On 19th April I tried again with the SBIG ST2000XM CCD camera and managed to record Deimos “off the vanes” as I fitted tube rings and rotated the OTA in the rings.
At this stage, I’m thinking that Phobos is too faint and too close to the Martian disc for the 7 inch Mewlon to resolve. Tom used a 10” instrument to dig it out of the planetary glare.
Cheers
Dennis