NavList:

Stan, you wrote:
"I question whether it was that much help in identifying constellations prior to morning twilight."

I'll go beyond that and say that the Rude star finder (or H.O. 2102-*) is a miserable beast. It's nothing more than a mediocre planisphere with altitude-azimuth grids attached. There are better ones available for a few bucks including the very nice design created by David Chandler and sold as "The Night Sky" which Bill has already mentioned. And it's easy today to print your own alt-azm grids and add them to one of those cheap planispheres if you really like the scales. Of course, many navigators develop attachments to this rude device, this "ugly duckling", hoping one day it will become Cygnus the Swan (a constellation that a cheap planisphere will display as a recognizable cross shape lying along the Milky Way, but the Rude star finder shows only as a single dot). I suspect that a lot of this has to do with the visceral pleasure of learning the stars for the first time. No matter how you do it, whatever device or system you use to learn the stars and constellations for the first time, it will always occupy a warm spot in the observer's heart. 

But let's talk about the utility of such a tool for a modern observer. The stars shift in predictable ways from night to night. Suppose you are sailing from New England to Barbados, and you intend to use celestial as much as possible. You will be sailing at an average speed of 8 knots, heading more or less SSE. The night before your voyage in mid-twilight, you step outside, and you see several navigation stars. There's star A 30° high in the east. Star B is 60° high in the south. And stars C and D are 45° high in the NNW and WNW. You make a mental note of those positions. Maybe you even write them down on a notecard. You depart at 0900 and twelve hours later, you're ready to take evening twilight sights. Oh, but it's cloudy, so you miss a day. The next night is clear. So where are those stars from two nights earlier? You tell me. Without a star finder, but knowing that you have travelled SSE at 8 knots for 36 hours, where you will find those stars A, B, C, D. This is the sort of basic positional astronomy that a celestial navigator really should know. And it's not complicated. You know what happens when you move 4.8° towards or away from a star. But even if you guessed that the stars are in the same positions that they two nights earlier on shore, would you have any difficulties identifying them on that second evening of your trip? That's the reality with ocean-sailing: you know the stars from the previous night's or morning's observations. The one really big exception to this reality --and one that mattered a great deal in the period when the star finder was in practical use-- is when a navigator is dumped aboard a vessel with no preparation possibly thousands of miles from home, maybe under southern hemisphere stars when he has only previously seen northern hemisphere stars.

If you like historical re-creationism, and if your favorite era is the middle 20th century, then the star finder is a tool appropriate to your re-creationist endeavors. Go for it! But if you're a modern navigator, there's little excuse for using it, except, of course, that natural affection I mentioned above. There are vastly better software apps for every class of device, and if you're afraid of running out of power, there are common analog planispheres widely available. Better yet, learn the stars before you sail. You'll have more fun. And don't recommend this goddamn Rude beast to a novice navigator or a beginning navigation enthusiast --unless you're a sadist.

-FER