Mars and Comet C/2012 S1 ISON will be within two degrees of each other in the morning sky in September 2013 and within one degree of each other in October 2013.
I was using SkyMap Pro recently to get an idea of how high in the sky Comet C/2012 S1 ISON will be in the fall.
I noted that Mars and Comet C/2012 S1 ISON will be with two degrees of each other in the morning sky in September 2013 and within one degree of each other in October 2013. So using SkyMap Pro I generated sky maps as they may be helpful to observers attempting to locate the comet.
In addition I have included tables listing the phases of the Moon for September and October.
The first map shows the track of Mars and Comet C/2012 S1 ISON from September 15th through October 15th. Both Mars and Comet C/2012 S1 ISON are in the constellation of Cancer in September and are in Leo in October.
On the maps there are track marks for every five days. The track marks on the left are Comet C/2012 S1 ISON while the tracks on the right are Mars. You will note that over time they are getting closer to each other.
The second map below shows the approximate 4 degree field of view through my TMB 105mm with a TMB 40mm 2" Paragon of Mars and Comet C/2012 S1 ISON on September 15th. It indicates that both Mars and the comet should fit into the same field of view.
However at this point it appears that the comet will develop more slowly in the autumn sky than originally thought, and may not reach naked eye visibility until November.
On the other hand if you have access to dark skies and a larger aperture telescope or do astrophotography you may be able to use Mars as a guide to locating the comet.
Here is a link to the sky maps and tables listing the phases of the Moon for September and October: