Binocular scale image showing the path of comet C/2013 A1 Siding Spring and Mars during October. Click to embiggen and print.
The pair are at their closest on October 19, when at 18:51 UT they will be a mere 1' 51" apart. Unfortunately, this will only effectively be seen from Africa. From the SSO scopes the closest the pair get is 18' 38" before the limit of western travel is reached.
Unless you have been living in a cave this past year you will know this October is the month that comet Siding Spring comes close to Mars.
Simulated view in Celestia of Siding Spring passing Mars. Although the tail appears to pass beteen Mars and Phobos this is a rendering artifact. The comet is well beyond Demios (the dot near the centre).
Passing 138,800 Km from Mars, comet Siding SPring comfortably misses the red planet. For comparison. Mars's outermost Moon Demios circles the planet at around 20.000 km from Mar's surface (on the other had, the average Earth-Moon distance is 384,400 Km).
A small flotilla of spacecraft are getting ready to either observe or avoid the comet. While the comet itself will miss Mars, the planet may be enveloped in its coma, and there is the possibility that cometary dust and debris will damage the spacecraft. Nonetheless, we are preparing for a bonanza of space based observations.
Chart of the path of C/2013 A1 (Siding Spring) from 29 September to 13 October, as seen from the SSO scopes at the end of Astronomical twilight. The large rectangle is the field of view of T12 and the small that of T9. Click to embiggen and print.
As well as all these spacecraft, amateurs and professional alike are eagerly watching the comet. in the lead-up to the encounter, and will be watching the encounter itself and its aftermath.
The comet would be interesting in its own right being relatively bright (around magnitude 9) and passing through some stunning astronomical territory.
Comet Siding Spring near the globular cluster NGC 6496 on 26 September. 10x60 second luminance exposures on T12, SUMMED in ImageJ.
You may need to do a MEDIAN combine when stacking images to bring the tail out at its best (messes up the pretties but you can do a separate image emphasising the clusters and so on).
As well as the standard Luminance exposures, if you can take some RBV images that would help the science missions as well (allowing definition of dust to gas ratios etc).
Chart of the path of C/2013 A1 (Siding Spring) and Mars from 13 September to November, as seen from the SSO scopes at the end of Astronomical twilight. The large rectangle is the field of view of T12 and the small that of T9. Click to embiggen and print.
The biggest challenge will be getting images of Mars and Siding spring in the same frame.
With the comet around magnitude 9, and Mars at magnitude 0.9 the difference is enormous. As well, the CCD's on the iTelescopes are highly sensitive. To take an image of Saturn on T27, ype de Lang used an exposure of 0.009 sec (!!!). Other approaches are to use a shorter exposure combined with an extreme filter like a hydrogen filter. Even then Mars will be tiny in all the iTelescopes!
Mars imaged for 1 second using the Ha filter on T9.
Whichever approach you use, you can't get the comet without over-exposing the planet, so you will have to assemble images from separate exposures (ie maybe shoot 10x60 second exposures for the comet and say 2-3 0.009 second exposures of the planet). Obviously some practise will be required to the the exposure parameters right before the night of the actual encounter.
Outside of the big day there are several nice encounters with clusters and such.
On October 3 the comet is around one degree from the open clusters NGC 6400 (Mag 8.8) and Cr 338 (Mag 8.0). Outside of T12 a mosaic may be the best way to approach this.
On October 4-6 the comet is within T12 distance of the large and beautiful open cluster Ptolemy's cluster (and a number of smaller ancillary ones). This is best taken as a T12 mosaic with come judicious exposure juggling.
On the 8-9th the comet is within 30' of the Butterfly Cluster M6 (it actually crosses the cluster, but this won't be seen from the SSO scopes) and NGC 6416. However, the Full Moon will be a problem (except early on the 8th, during the total Lunar Eclipse :-)
On the 11-13th the comet is within T12 distance of the open clusters Tom Thumb Cluster (Mag 8.2), Cr 347 (mag 8.8) and Cr 351 (Magnitude 9.3). The comet is fading so longer exposures or more stacking shots will be needed to bring out the comet, but will also bring out the background stars, obscuring the comet tail.
Large mutipanel mosaics with T12 will bring in the Triffid and Lagoon nebulas, however, the shortening length of time before the comet goes below the travel of the itelescopes limits these kinds of mosaics.
On the 21st the comet will be within 19' of the globular cluster NGC 6401 (Mag 7.4).
The MPC one line ephemeris is
CK13A010 2014 10 25.3017 1.398713 1.000431 2.4225 300.9763 129.0428 20141209 8.2 2.4 C/2013 A1 (Siding Spring)