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Alex, you wrote:
"I missed your survey"

Sorry for the confusion. I meant a "foot survey": I visited more than a dozen stores looking to see which calculators are "readily available" for $10 or less and include the usual "scientific calculator" functions necessary for navigation calculations. The winner, as I mentioned is the Casio fx-260 Solar. In second place, there's the TI-30Xa, which is about the same price and capability, but I don't like it as much (despite my fondness for my TI-30 from 1976 which still works well, even though it takes over one second to generate the value of a trig function).

You wrote:
"I am using a very old Casio fx-250, which has been discontinued long ago."

Now that you mention it, I am quite sure we discussed this before (five years ago... or more??). I have that calculator, too, and I like it. While doing my survey, I also checked eBay for prices, and I found that there are quite a few of these fx-250's available in "near new" condition. But they're around $20 or more, and I can't see any benefit anymore compared to a brand new fx-260 Solar.

You added:
"Several years ago I bought Casio fx-260 solar, and it does not have this convenient deg/min/sec conversion."

Aha. Yes, that rings a bell from our discussions years ago. Of course, they "improved" that feature on the 260, from the perspective of many users, but for us it's a downgrade. On the older calculator, you could enter 10° 30.5' using the [° ' "] key, and it would work correctly and immediately display the decimal equivalent. On the newer calculators, it's no longer possible to enter decimal minutes, and also it does not display the decimalized angle. But it's no big deal. For students, I really recommend that they do their own decimalization: deg+min/60+sec/3600. It's not many more keystrokes, and it yields better understanding.

The current version of the fx-260 Solar is a bit larger than the one sold five years ago. It has better power management, and it works better in low light. You can use it at night with low-level indoor lighting, and if the solar cells are briefly covered, the calculator remains functional for about 20 seconds. The larger size of the calculator may accomodate a capacitor, but I would guess the size change is primarily ergonomic. It's easier to work with.

The attached photo shows a roughly ten-year old fx-250, and ten-year old and brand new examples of the fx-260 Solar. Hard to complain for $8.47.

-FER

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