An air carrier Captain took exception to being assigned to fly an aircraft on which the standby instrument system was deferred. He felt the company failed to provide adequate enroute weather information to ensure compliance with the requirement that the aircraft be operated only in daylight/VMC conditions.

Narrative

Aircraft was dispatched into and out of an International city with a deferred ISI [Integrated Standby Instrument system]. This MEL requires that the aircraft be operated in Daylight VMC conditions. The flight was dispatched so as to arrive at our destination before twilight and before sunset (by about 25 minutes). There was a broken layer initially at the departure airport. There were no airport station weather reports given in the dispatch release/weather package. The crew was expected to maintain VMC and avoid VFR Over the Top for 656 miles across international airspace. The aircraft had been [operated] with this MEL item for two days.This event was the result of pushing the Dispatcher and crew to meet completion goals. Serious consideration was not given to the ability to maintain VMC conditions. It is ludicrous to think that VMC conditions could be maintained for over 656 miles no matter what time of year it is. This event occurred because the aircraft was dispatched to a station and from a station where VMC conditions could be maintained. The main issue at stake is that the crew was not contacted by the Dispatcher regarding weather conditions along the flight path. It became the crews' responsibility to verify the entire route and check weather stations along the way.The crew had no way of determining if the flight could be dispatched legally under this MEL except to say that if they could take off legally; and maintain VMC; they would have VMC conditions at the destination. If IMC conditions were to come up along the 656 miles the crew would have to divert to VMC conditions. This is stressful for any crew. This flight should not have been dispatched and if I could do it over again; I would have left the aircraft.Contact was made via ACARS to the Dispatcher and weather stations along the way were identified. The Dispatcher was notified that should the flight encounter IMC conditions; a diversion was going to take place. The dispatcher agreed.In the future; [I won't] do it. This MEL item is for the purpose of getting a flight BACK to a destination NOT to fly with it for two days. This is very disappointing.