Mars and Deimos, 9th & 19th April 2014, Brisbane

[Dennis]

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

[h0ughy (David)]

how cool is that - your the man - again Mr simmons

[RickS (Rick)]

Originally Posted by h0ughy

how cool is that - your the man - again Mr simmons

+1, Dennis! It's truly amazing what can be done with "amateur" gear these days.

[John Hothersall]

Great catch considering diff spikes and faintness of moons. I'll need a shorter FL to get these.

John.

[von Tom (Tom)]

Excellent work Dennis. Very clean and clear images as always!

Cheers,
Tom

[Dennis]

Thanks David, Rick, John and Tom, I appreciate your comments.

@John – this is the 1st time ever that I have read of an astronomer wanting a shorter focal length!

I took a series of exposures from 1 sec right up to 60 secs and have since measured the flux around the expected position of Phobos. Unfortunately, the background levels in the region of Phobos are some 5 to 6 times brighter in the 1 sec frames that the expected brightness of Phobos, so I’ve got Buckley’s chance of digging it out!

Cheers

Dennis

[sheeny (Al)]

I always love your work, Dennis!


Al.

[blink138 (Pat)]

extraordinary!
pat

[Derek Klepp]

Thanks Dennis a good read on a showery night down here.I must have a go at this with the 16" Dob and the Gstar t see if I can get it live on screen.

[Dennis]

Thanks Al, Pat and Derek, I appreciate your comments.

@Derek – just check for the best Phobos E or W elongations where Phobos can be up to 21 arc secs away from Mars and I think the 16” should reveal it nicely.

Cheers

Dennis