NavList:

Bill,

I now have 2 cheap "programmable" calculators.

1)Texa TI-36XPRO as recommended by Greg Ruzinski. It can take 2 cel nav programs.£15 0n Ebay new. I use mine for Thompson lunar clearance as per Frank's description.

2) More recent aquisition is the Casio fx-3650P. £25 on EBay, new. This takes 4 programs.I have loaded i)Cosine formula for  Hc and Az (as one formula). ii) Direct lat and long from simulataneous  timesight 2 body Alts as per Karl page 78.iii) Cosine lunar clearance as per Karl page 93, iv)Letcher lunar. I need the Letcher and Thomspon lunars to check my Margett tables which have the same inputs.

Both work perfectly, quicker than smart phone, battery lasts forever, (whereas smart phone needs daily charging and is not seaworthy) very seaworthy in plastic sandwhich bag and I find much easier and more stable than smart phone, especially the "touch screen" which is not good for cold wet arthritic fingers. Traditional clunky buttons on the calculators I find much better.

So I'm a new fan of cheap programmable calculators. Never looked at them in the past because of the expense, which is no longer an issue as prices have tumbled..

The Casio for £25 does everything I require. (So does my Fuller 3 AHA Cel Nav slide rule!)

Best wishes

Francis