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| Mars, showing rotation over 90 minutes |
Type: Planet
Constellation: Pisces
Distance: 45 million miles
Equipment: Phillips TouCam Pro, x2 barlow, Celestron C9.25, Vixen GPDX mount
The above gif is made from a series of images of Mars, and shows the rising of the feature of Martian geography known as Sirtis Major over the eastern limb of the planet over a period of about 90 minutes.
The evening of November 7th was a foggy, soggy one, but Mars was very visible above the vapours and the evening represented one of the few opportunities I had to try and photograph the planet during its current opposition.
Mars made its most recent close approach to Earth on October 6th, when it was 38.5m miles away and appeared around 23 arc-seconds across in the sky. It won’t get that close again until September 2035, an event I am unlikely to witness.
The closest Mars ever gets to Earth is about 34.5 millions miles and thus never appears to be more than around 25 arc-seconds across, effectively still looking like a bright star. Bear in mind that the full Moon is around 30 arc-MINUTES across and you can see how stupid social media stories of “Mars as large as the full moon” really are.
Although a month past opposition, Mars was still a respectable 18.8 arc-seconds across and at magnitude -1.9, was brighter than any star and nearly as bright as Jupiter, which was setting in the west.
To photograph Mars, I set up my old Celestron C9.25 SCT, and used an ancient (c. year 2000) Phillips TouCam Pro webcam as the image capture device.
Planetary details are extremely small and views are constantly distorted by atmospheric fluctuations. Using a video camera to record 20 or 30 frames a second for a minute or so gives a bank of thousand or so pictures that can be processed by software (I use Registax) that selects the sharpest few frames and stacks them together to give a detailed result – in theory. In addition, Mars has a day that is about the same length as Earth’s and it therefore rotates quite quickly: a video longer than about a minute will suffer from blurring caused by the movement of planetary features as the planet spins on its axis.
In practice, achieving a sharp focus on an image that is bouncing around your laptop screen like a demented ping-pong ball is a pretty tall order, and conditions have to be exceptional to get images that show much detail. This wasn’t one of those evenings, and indeed, I gave up at around 8.30 because the dew was dripping off of everything and was worried it would get into the electrics!
Nevertheless, the individual processed image stacks showed up recognisable features when compared with the BAA’s Mars mapper…
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| Mars at 19.30 compared to BAA map (click on image to enlarge) |
My image shows a hint of the Martian phase at the time (97%) which is not shown on the Mars map above.
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