Mars with Phobos and Deimos from Brisbane - 6th Oct 2020

[Dennis]

On Tuesday, October 6th 2020, Mars had a close encounter with Earth, albeit some 62 million km (38.6 million miles) from my back garden in Brisbane.

On that evening, Fear and Dread also stalked the night skies in Brisbane, namely the 2 small moons of Mars, Phobos (Fear) and Deimos (Dread). Both moons were discovered in 1877 by Asaph Hall. Ninety-four years later, NASA's Mariner 9 spacecraft got a much better look at the two moons from its orbit around Mars.

I managed to record images of these diminutive moons of Mars from my back garden in Brisbane, around 22:00 on 6th October 2020. Intermittent clouds meant that I didn't record the LRGB frames until 1 hour later.

Mars is 6794.0 km in diameter and had an apparent size of 23 arc secs when I captured these images, shining with a magnitude of -2.57.

Phobos had a magnitude of 10.6 located some 30 arc secs from the disc of Mars, with Deimos a little dimmer at magnitude 11.7 and further away at 73 arc secs.

The larger moon is Phobos, a small, irregularly shaped object measuring just 22.7 km across with an orbit that places it closer to Mars than Deimos. Compared to Earth’s own Moon — which orbits at a distance of 384,403 km away from our planet — Phobos orbits at an average distance of only 9,377 km above Mars. Phobos is seven times more massive than Mars’s outer moon, Deimos.

Mars’ second moon is Deimos. It is even smaller, measuring just 12.6 km across, and is also less irregular in shape. Its orbit places it much farther away from Mars, at a distance of 23,460 km, which means that Deimos takes 30.35 hours to complete an orbit around Mars.

I have overlaid my LRGB image over the blown-out disc of Mars, which I had to grossly over-expose to record the much fainter moons. I have also uploaded a Screen Capture from SkyTools 4 Imaging to identify the moons.

Tak Mewlon 210 F11.5, Tak x1.6 Extender, ASI290MM Camera.

Cheers

Dennis

[jahnpahwa (JP)]

Sensational capture there, Dennis!

I learned from your post, too, so thank you

[multiweb (Marc)]

Nice catch Dennis. Good write up and excellent capture to boot.

[cometcatcher (Kevin)]

Very nice shots of Mars and the moons! Love it!

[Tulloch (Andrew)]

Great images Dennis, these two little moons are really hard to capture, excellent work.

[Dennis]

Thanks for the comments and feedback folks, I appreciate them.

What a difference a month makes – I have had several epic fails, the last one earlier in September.

Since then, I simply rotated the OTA in its mounting rings and lo and behold, Phobos just popped right out of the spider diffraction spikes.

I was totally surprised at how easily Phobos and Deimos were revealed once I had rotated the OTA in the rings – thanks Matt (he designed and provided the Mewlon rings).

Cheers

Dennis

[Dennis]

This is data just keeps on giving , so I overlaid the orbital paths of Phobos and Deimos over my image. Paths were obtained from Starry Night Pro Plus 8 with a SNP8 screen capture attached.

On 6th October 2020 as viewed from Brisbane, Phobos was at Western Elongation at 23:08 and so when I grabbed this particular sequence, Phobos was some 0 hours and 32 minutes before reaching Western Elongation.

I have also annotated an image listing the SER File capture times from FireCapture to show the positions of Phobos along its orbital path from 22:21:33 through 23:53:05.

The gaps in timing were mainly due to clouds obscuring Mars, plus an uncommanded BSOD and computer restart incident.

Cheers

Dennis

[Atmos (Colin)]

Absolutely fascinating Dennis! I always imagined that they were considerably fainter than they were.
Also great that you could capture the movement of Phobos over time

[sheeny (Al)]

Love your work Dennis.


Al.

[Zubenel (Wes)]

Amazing as usual Dennis ,. Im headed to the Backyard tonight to hopefully capture. no promises but what was your typical data set capture time? I'll be shooting AVI and convert to .SER to stack.... I think...

[Dennis]

Originally Posted by Zubenel

Amazing as usual Dennis ,. Im headed to the Backyard tonight to hopefully capture. no promises but what was your typical data set capture time? I'll be shooting AVI and convert to .SER to stack.... I think...

Hi Wes

Good luck, we're clouded out down in Brissie.

Here are the FireCapture Log Files for Mars LRGB and then the Moons:

FireCapture v2.6 Settings – MARS LUM
Camera=ZWO ASI290MM
Filter=L
Profile=Mars
Diameter=22.55"
Magnitude=-2.57
CM=82.5° (during mid of capture)
Filename=Mars_234032.ser
Date=061020
Start=234017.055
Mid=234032.055
End=234047.055
Start(UT)=134017.055
Mid(UT)=134032.055
End(UT)=134047.055
Duration=30.000s
Date_format=ddMMyy
Time_format=HHmmss
LT=UT +10h
Frames captured=3490
File type=SER
Binning=no
ROI=1024x768
ROI(Offset)=0x0
FPS (avg.)=116
Shutter=1.800ms
Gain=300 (50%)
AutoExposure=off
FPS=100 (off)
SoftwareGain=10 (off)
AutoHisto=75 (off)
Gamma=50
HighSpeed=off
USBTraffic=80 (off)
AutoGain=off
Brightness=1 (off)
Histogramm(min)=0
Histogramm(max)=218
Histogramm=85%
Noise(avg.deviation)=n/a
Limit=30 Seconds
Sensor temperature=26.2°C

FireCapture v2.6 Settings – MOONS LUM
Camera=ZWO ASI290MM
Filter=L
Profile=Mars
Diameter=22.55"
Magnitude=-2.57
CM=67.0° (during mid of capture)
Filename=Mars_223706.ser
Date=061020
Start=223609.480
Mid=223706.329
End=223803.179
Start(UT)=123609.480
Mid(UT)=123706.329
End(UT)=123803.179
Duration=113.699s
Date_format=ddMMyy
Time_format=HHmmss
LT=UT +10h
Frames captured=100
File type=SER
Binning=no
ROI=1936x1096
ROI(Offset)=0x0
FPS (avg.)=0
Shutter=1.00s
Gain=300 (50%)
AutoGain=off
Brightness=1 (off)
AutoHisto=75 (off)
AutoExposure=off
SoftwareGain=10 (off)
Gamma=50
USBTraffic=80 (off)
HighSpeed=off
FPS=100 (off)
Histogramm(min)=0
Histogramm(max)=255
Histogramm=100%
Noise(avg.deviation)=n/a
Limit=100 Frames
Sensor temperature=23.6°C

[Tulloch (Andrew)]

Nice images there, why don't you try turning these stills into an animated gif or png? Would love to see Phobos/Deimos track along the orbital paths you've drawn...

[DavidTrap (David)]

You are the master of this stuff Dennis!!!!

DT

[Dennis]

Originally Posted by Tulloch

Nice images there, why don't you try turning these stills into an animated gif or png? Would love to see Phobos/Deimos track along the orbital paths you've drawn...

Originally Posted by DavidTrap

You are the master of this stuff Dennis!!!!

DT

Thank you Andrew and David, I appreciate your comments.

I reviewed the data that I had captured, but as there were gaps because of intermittent cloud cover, I didn't get enough LRGB set of mars to make an animation.

Cheers

Dennis