If I know IV at open can calculate the price and vice versa. At the Open know neither. IV at the subsequent, published Close cannot be used since IV is not constant during the day. How is the price or IV calculated at the Open?
I need this for back testing. Do not have funds to pay for data.

I'm creating this topic to discuss one of the most important aspect of options trading - Implied Volatility.
 
We will discuss examples how IV impacts our trades. 
 
I welcome questions from members and forum guests (registration required).

Did anyone buy strangles or straddles on healthcare stocks, hoping for an IV rise prior to the decision by the Supremes?
I took a look at http://www.optionistics.com/ on stocks like UNH, ESRX, WLP, AET, HUM and CI and it seems most of them already (except ESRX) have seen a spike in IV vs. historical volatility. So, I'm guessing it's probably too late to buy before the Supremes make their decision known.
Maybe someone could trade on the IV crush that might happen afterward, but I'm a bit too chicken to try that, in case those stocks make big moves.
edit: I found some other possible plays at http://www.zacks.com...in-the-balance and http://money.msn.com/top-stocks/post.aspx?post=fbad2fea-0d2f-4146-9239-d98f13f3e519.