Subject: Re: Buying Long Dated Calls
You'd get a more accurate view by plotting the ASK, because you are assured you can get it at the ASK. The ASK is undoubtedly from a market maker.

I don't think this is true. Someone placing a limit order to buy inside the spread pushes up the bid. And someone placing a limit order to sell inside the spread pushes down the ask.
I do about the same number of transactions on the buy and sell side, and the effect is symmetrical.

Elan