Ship spotted "Long Range"

[black1]

When WO calls out this and says long range, what usually is the range, i tend to keep seeing 9,000km or roughly 5miles out. Is this usually the range estimate? I ask this because it is difficult when establishing distance to target without visual by me to start an interception course when not using "map-contact updates". I guess in order to know which way to intercept all I can go on is "constant distance", "moving away" etc and try to plot his course. Please give tips on playing without "map contacts updated", thanks.