The secret sign that Apple’s a buy

While Apple analysts obsess over iPhone sales and the number of new iTunes accounts as we await Tuesday's earnings, there's a less obvious indicator that could be the better predictor of where Apple shares will go. And right now, it appears to be flashing a serious buy signal.

That indicator is the Apple VIX, which measures the expected volatility in Apple shares by looking at the prices of options on Apple. The Apple VIX shows how much people are willing to pay to make bullish or bearish bets on Apple shares—bets that could either be speculative, or could hedge a position in the stock.

Based on the VIX, which indicates how much traders are willing to pay for "insurance" on the market by looking at the prices of options on the S&P 500, the Apple VIX uses the same methodology to look at the price of options on Apple.

So just as the VIX does, the Apple VIX "gives a gauge of fear," said Brian Stutland of Stutland Volatility Group. And its action this year has been very telling.

"Starting May 1, as Apple was falling, on each successive fall we saw this negative correlation, where volatility rose," Stutland said on Friday's "Options Action."

But the tell came in the middle of August, when "volatility rose very steeply in the last little plunge for Apple. What people were basically doing is just puking out their positions and buying insurance. And over the next few months after that, this negative correlation stops. And after Apple reaches its peak of panic and fear in the marketplace, we see fear start to subside."

Stutland said another key moment for the Apple VIX occurred at the end of June. At that point, "Apple makes about the same low, but yet volatility is cut by a third. Meaning that options traders were picking bottoms, and trying to buy into the stock. That was the moment to start to get long Apple."

So is it too late to buy now?

"The stock has already moved a little bit, but I like it. I think the downtrend has stopped in Apple," Stutland said. He sees Apple shares trading up to $450, and recommends buying a call spread to capitalize on this potential move.

Carter Worth, chief market technician at Oppenheimer, believes Stutland has a point. "I think Brian's characterization of it is perfect," Worth said. "He used the word 'bottoming-out' and said the downtrend has stopped, and that's what we see here."

Worth believes buying in now is a smart move. "The stock seems asymmetrical. You get long here and you're wrong, you don't get hurt. You get it right, and it's got a lot of pop."

That pop could come pretty soon. The options market is implying that Apple will move 6.8 percent off of Tuesday's earnings, which is bigger than the average implied move of 5.1 percent over the past eight quarters.

If that move comes to the upside, Apple shares will rise above $455—making Brian's bullish trade a big winner.

—By CNBC's Alex Rosenberg. Follow him on Twitter: @CNBCAlex.

Follow the show on Twitter: @CNBCOptions.