What can you expect to see in your scope?  The following diagram shows the best possible resolution view on February 1, 2010 as seen in instruments with apertures ranging from 3.5" to 18".  Now before you go out and buy a larger scope, it can't be stressed enough that these are the best possible resolutions.  In practice you will be lucky to see the detail present in the 90 mm ETX view in any size instrument!  In fact, when placed side-by-side larger scopes will sometimes yield poorer views unless they are carefully collimated and have reached thermal equilibrium with their surroundings. Mars must also be high in the sky to achieve these results.

North is down and east is to the right, matching the view in the majority of the telescopes simulated.

All simulations via our SkyTools 3 software.