https://docs.deribit.com/ (link will be changed in near future to
www.deribit.com/docs )
read 1.4 and 1.5.
we calculate ourselves, there are various "indexes" online, some are not transparent, and with some we simply disagree, we decided to go with our own, though maybe not perfect, we do our best. We take 5 exchanges, take the average of bid-ask from each, dump the highest and the lowest (flash crashes etc, mtgox stories), and take the remaining 3 values (or less if a signal is broken) and take the average of that...thats our index. Further the last half hour before expiration, every 6 seconds we take the index value...for half an hour...and the average of that will be settlement price. (Expiration price.) At the moment we dont even have "in between" settlements, all intermediate gains/losses count to your available balance, either for withdrawal or trading.
We choose for only half hour settlement period...its easier for trading...once we enter this timeframe, pretty soon it becomes clear where we are gonna end up. During this half hour an estimated settlement price is shown in the trading table, which is calculated with all past values, and all future values being assumed being same as last value. (this is the best estimate one can give during this last half before expiration).
Further we have a page dedicated to the index,
https://www.deribit.com/main#/prinx_chart, where you can see a graph of the index, as well as a table with the 5 exchanges, colored either red (not part of index at the moment) and colored green. (part of index at that moment.)
