The 2014 Opposition of Mars

The 2014 opposition of Mars was due to take place in mid-April, with the planet in the constellation Virgo at a declination of about -5 degrees. Mars was expected to peak at -1.5 magnitudes with a maximum diameter of 15.1 arcseconds. For Northern Italian mid latitudes (~ 45 degrees N), this yields a maximum height of 40 degrees at the local meridian. Considering the average seeing conditions in the area, the geometric circumstances were not super-favorable, but nevertheless fair enough be worth a try. After all, the next Mars opposition with good observing conditions for the northern temperate latitudes will only take place in 2020.

Therefore, I grabbed my good ol’ C11, a couple of high-quality planetary cameras, and I kept patiently waiting for the right moment to image the planet. Let’s see how it worked out!

As usual, spring in the temperate zones is largely unpredictable, and April 2014 was no exception. However, we did have some spells of good weather, during which a few days sometimes offered seeing conditions decent enough to distinguish (and image) the details of the planet’s surface.

In the end, I managed to observe (and image) Mars on five nights: April 6th, 10th, 16th, 22nd and 23rd (of which the best was April 23rd while the worst was April 16th), using mainly the ASI and iNova cameras through an IR-pass filter (Schott RG695). The IR-pass filter in instrumental in mitigating the effects of air turbulence and increasing the contrast of features of the martian surface. I also managed to make some tricolor images, even if the final result is of far lower quality than that obtained with the IR-pass filter.

Of the two cameras I used, the iNova (which has a Sony ICX 618 sensor) is probably a tad more sensitive than the ASI which offers a very good price/performance ratio, despite having a CMOS sensor. On the other hand, iNova’s pixels are quite bigger than those of the ASI (5.6 vs 3.75 um), so that one has to push up the equivalent focal length in order to get a decent-sized disk on the sensor.

Given Mars’ small apparent diameter, I always had to work at focal ratios ranging from f/36 to f/46, i.e. at equivalent focal lengths in the 10 to almost 13 m range, which poses a number of challenges to the imaging setup. These “unusual” and quite high focal ratios were obtained by using a 3x Televue barlow lens and further increasing the distance from the sensor to the lens with the filter wheel and an extension tube.

Below you can find some pictures of Mars, among which a GIF animation made from of six movies acquired on April 23rd, 2014 over a timespan of around twenty minutes. All acquisition details are written in the caption of each image.

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