In order to stream SkyGo over a VGA cable (or S-Video as would appear to be the case for your cable), you will need to use a jailbreak tweak such as DisplayOut which forces the iPad to output video over a cable, even when not supported by the App. I've just tested it with my own (official Apple) VGA cable, and it will only receive an output from SkyGo when my DisplayOut tweak is enabled. When disabled I get the message saying that external output is not supported by the app.
There may be some other tweaks which also enable these features. DisplayOut is simply the one I rely on.
As giradman pointed out, the HDMI cable and Airplay are also viable options.
Hope that helps.