NavList:

Ronald van Riet, you wondered:
"I don't want to spoil any fun, but how long does a solar calculator last at night?"

They work under very low light levels. A small lantern or flashlight is more than enough to power up the Casio fx-260. If the lighting is bright enough to read with minimum comfort, then it's bright enough to power up a basic solar calculator. May I suggest a similar complaint which might have been raised a hundred years ago: "Yeah, sure, that slide rule thing is great in daylight! But what are you gonna do in the middle of a dark night?"

But let's go for the theoretical case and imagine that you have no light source bright enough to light up a solar calculator. How are you then limited, if you use traditional celestial navigation?

• You have Sun sights all day long totalling twelve hours on average, no problem. Sailing in summer, more like 14 hours a day.
• Early morning twilight sights add another hour or so. Also no problem because you can wait half an hour for morning light to work up the sights.
• Evening twilight sights, which would add yet another hour to the 12 or 13 (or 14 or 15) already available, well, here you would be at a disadvantage without light, but this is true whether you're using a calculator or paper methods. 

Modern calculators are incredibly reliable and inexpensive. Solar scientific calculators, like the Casio fx-260, are ubiquitous and cheap thanks to their popularity in classrooms. My biggest concern about these wonderful devices in the long term, meaning five years in the 21st century, is that they may well become superfluous in the classroom, and that will crash the market. At the secondary school level (American high school), it is becoming increasingly common to supply a basic laptop or chromebook to every student. Basic chromebooks currently sell for $150, and frequently less than $75 lightly used. These are price levels comparable to much less capable programmable calculators. Perhaps students don't need calculators at all. Standardized testing, where laptops are still prohibited, may be the last bastion of the basic scientific calculator. Will that be enough to keep them in production at the low prices we see today? In a single year, the price of the Casio fx-260 at a local Walmart has fallen from $8 to $7. That's good for the consumer, but is there profit for the manufacturers and merchants?

Frank Reed