Istanbul is 7 hours behind Melbourne
Best overlap: 3:00 PM to 6:00 PM in Melbourne is 8:00 AM to 11:00 AM in Istanbul.
If you set up a recurring sync, 3:00 PM to 6:00 PM in Melbourne (8:00 AM to 11:00 AM in Istanbul) is the natural home for it. Istanbul is 7 hours behind Melbourne, which gives you a solid 3-hour window. Book earlier in it and neither side is rushing. These times hold for most of the year, but Melbourne's daylight saving (which Istanbul doesn't use) shifts them by an hour twice annually.