So I've gone over the CBOE VIX white paper a few times and understand it well enough to have written (Ruby) code to produce the correct VIX. I have the older version of the paper where it only used standard/monthly options to produce the number (published in 2009) and I also have the most recent paper published in 2014 that modified the rules to use weekly options. I understand the differences and why they updated their rules.
Here's the white paper: http://www.cboe.com/micro/vix/vixwhite.pdf
Now I want to calculate the 60-day VIX. Please confirm that I'm on the correct path in modifying the rules and the formula.
Instead of picking options that expire between 23 and 37 days out, I'd want to grab the series that expire between 53 and 67 days out.
In Step 3 of the formula (as listed in the white paper), use number of minutes in 60-days for N(60).
As a consequence of 2, we are weighting to a 60-day timeframe. To do a 90, 120, 150, or 180-day VIX I would make similar changes as above.
Does this make sense or have I made a fundamental error?