NavList:

Alan,

You wrote:

I have often wondered as to why these wonderful electronic calculators aka electronic slide rules weren't made with BOTH battery and solar powered capabilities.

This is one reason I prefer the Texas Instruments TI-30X IIS over the Casio fx-260. The TI has both solar and battery power. Whenever the ambient light is not enough to prvide a clear display from solar power, the batteries automatically kick in. When there is enough light, the solar panel is used to conserve battery power. (I'm not sure if the two sources can work in combination.)

I have found that, even in my living room with four "can lights" on, there is insufficient light to get a sharp, clear display on the Casio. I have to resort to using a flexible LED desk lamp, which is very bright and somewhat distracting.

An added benefit of the TI is that it can store up to five variables. This is very convenient when doing sight reduction calculations and lunars. For SR, I usually store my DR or AP latitude as "B", the declination as "D", the LHA as "A" and the H_c as "C". (I don't usually store the azimuth as it is the last step in the calculation.) When calculating lunars using Frank's "easy lunars" formulae, I first store the Moon's altitude as "C", the other body's altitude as "D" and the LD as "E". I then calculate "A" and store it as...you guessed it: "A", "B" as "B" and finally "Q" as "C" (replacing the Moon's altitude, which I no longer need)*. All I have to do next is enter "E+[-DH_Moon]A+[-DH_Star]B+C"; where "DH_Moon" is the difference in altitude of the Moon in degrees and decimal minutes, etc. I find it all to be very natural, intuitive and fast.

*The calculation for "A" looks something like: "(sin(D)-cos(E)sin(C))/(cos(C)sin(E))->A". The calculation for "Q" looks like: "(0.55(DH_Moon²)(1/tan(E))(1-A²))/3438->C".

Regards,

Sean C.

PS

Frank, you have stated before that the Casio fx-260 is a requirement for some of your classes. Would you allow a TI-30X IIS if someone felt more comfortable using it?