Frequently Asked Questions.
C. Running Orbiter
Assuming you have configured the video and other options in the Orbiter Launchpad dialog, you are ready to take off. Pick a scenario from the list, and click the "ORBITER" button.
To reach orbit from a planetary surface, you need to do two things: attain sufficient altitude, and sufficient tangential velocity. The first point is easy, but unless you reach sufficient tangential velocity, you will simply fall back to Earth again in a ballistic trajectory. The required velocity depends on the orbit altitude and planet mass. For example, a low Earth orbit (LEO) requires a velocity of more than 7000 metres/second.
The first step for a successful rendezvous manoeuvre takes place before launch. You should launch into an orbit with as little inclination to the orbital plane of the target as possible. This means waiting until the orbital plane of the target passes through your launch site (use the Map MFD to monitor this). By launching at the right time and into the right direction, you can minimise the need for later corrections of the orbital plane (once in orbit, you can use the "Align orbital plane" MFD for eliminating any residual inclination).
Once you got close to your target (see C3), use the Docking HUD mode and the Docking MFD for final approach. The Docking HUD contains relative velocity indicators which help closing in on your target. You need to tune your navigation radios to the target's transmitter frequency to make use of the docking instrumentation. (You can find the target's transponder frequency (XPDR) in the vessel info sheet (Ctrl-I). Set one of your navigation radios (Shift-C) to that frequency, and slave the HUD and Docking MFD to the appropriate receiver).
Orbiter now includes Duncan Sharpe's TransX MFD mode, which is a great tool for setting up interplanetary routes. You need to activate the TransX module in the Orbiter Launchpad dialog to use this.
All internal calculations performed by Orbiter are done in metric units (metre, second, kilogram, Joule, Pascal, etc.), for the simple reason that this is the only system I am familiar and comfortable with, and it is widely used by the scientific community. Likewise, all standard instrument readouts and data displays are in metric units (with very few exceptions, like the use of astronomical units (AU) for large distances). There is however nothing preventing an addon developer from implementing instruments which display their data in a different unit system, and it would be entirely possible to write imperial unit replacements for all standard MFDs. Just don't expect them to feature in the stock Orbiter distribution. If you want to see feet, fathoms, stones, barns or quarts, you will probably have to code them yourself.
The moon, as seen from Earth, covers an angular diameter of approximately 30 arc minutes (at a distance of ~385 000 km and diameter ~3 476 km, you can work it out for yourself). This is exactly the size at which it appears in Orbiter. There are two possible reasons why it may appear too small to you:
Too large field of view setting. If you want to see the moon and other objects in the simulation window at the same angular size as you would, for example, when looking out of a window, then the field of view (FOV) setting of the simulation must correspond to the viewing geometry. That is, the simulation window size and eye-screen distance. As a typical example, for a 19 inch monitor (4:3 aspect ratio) running Orbiter in full-screen mode, and a viewing distance of 60 cm, the correct (vertical) FOV setting would be 27 degrees. In practice, a much larger value is usually selected, to compensate for missing peripheral vision.
Optical illusion. People perceive the size of the moon to be much larger than it really is, in particular close to the horizon. Several explanations have been brought forward, for example http://www.noao.edu/outreach/nop/nophigh/steve8.html or http://facstaff.uww.edu/mccreadd/. You might want to take a photograph of the moon yourself, with a normal-focus length lens and including some trees or houses for reference. It is going to look smaller than you thought!