I am typing this on my old Palm IIIxe via its GoType keyboard. I've had this Palm PDA for over a decade and still rely on it for many simple tasks that I'm afraid smart phones aren't really good at. With the keyboard plugged in, it becomes an instant laptop, and many articles have been written on it.
I'm a firm believer, these days at least, in trying to do things more simply. There was a time when dragging a laptop into the field to do astronomy seemed logical. Now, I'm finding that it really gets in the way most nights I choose to do so. The only time the laptop gets used at all is for imaging.
Many astronomers use portable computers in the field for a number of tasks, including having a handy reference for star charts. There may be an easier way to go about this. What is needed is some prior planning.
For one, there are plenty of smart phone astronomy apps that allow you to guide your telescope, check the position of Jupiter's moons, check the phase of the Moon, etc. Smart phones, though, tend to be bright, even if you go to "night" mode.
This is where I found that e-readers have a real advantage.
Many of the lower end e-readers, whether they be low costs or simply older devices, use e-ink technology. They are not backlit, instead relying on external light. Their screens, though small, are very clear and easy to read. Perhaps most impressive is battery life; they can run for hours on a single charge. These e-readers make the perfect astronomical companion.
The two units I've used for my tests have been a third generation Kindle (Kindle 3) and a new Nook Simple Touch.
Of the two, the Kindle 3 shows the most potential. Not only does it handle a variety of e-book formats, it can also display JPEG's, PNG's and GIF's. Create a folder called "My Pictures" and place the images in there. When you access the folder, it launches the built-in image viewer. This viewer is able to zoom in on the image as well, so you do not need to limit yourself to the 600 x 800 resolution of the screen. The hotkeys on the Kindle 3 are "q" to zoom in, "w" to zoom out, "f" for full screen, "c" for actual image size and "e" for reset zoom.
PDF star charts are another matter on the Kindle. If you are not familiar with Taki Toshimi's star charts, you should be. These charts are fantastic, but they are also much larger than the screen resolution on an e-reader. In the case of the Kindle, you can zoom in. Be aware, however, that it can be a little sluggish.
The other e-reader I tested was my much newer Nook Simple Touch, one of the more inexpensive units out there. While the Kindle 3 has support for multiple formats, the much simpler Simpler Touch is limited to two, EPUB and PDF. Fortunately, images can be converted to PDF's easily with the right software. Unfortunately, on the Simple Touch, you are limited to the 600 x 800 resolution. This, sadly, eliminates the really nice Taki charts. There are still options, however, and the ones I want to cover are free.
A quick search on the Internet can provide you with plenty of free star charts aside from the ones mentioned, but it is very important to remember that these e-readers have very small screens, 600 x 800 on average. Roban Hultman Kramer has compiled a set of PP3 generated star charts that are designed to be used with the Kindle (for those unfamiliar with PP3, it was once used to provide the original star chart images for Wikipedia. It is not for the faint of heart, however). Installing them is very easy if you have one of the older e-ink models (he supplies instructions), and the charts are fairly easy to read, provided you switch to full screen mode. If you have a Nook Simple Touch, you will need to convert these images to PDF in order for them to be used. Also, they display ever so slightly smaller on the Nook, with no full screen, and unlike the Kindle, you can't page from chart to chart. The charts are still usable however.
Another option is to make your own star charts, using some of the various software packages and making sure to create images that are limited to the size of the screen (though, again, PDF's on the Kindle can be zoomed in on).
The final solution is to look for astronomy e-books, and there are many that have passed into the public domain. One of the books I have tried on both devices is "A Field Book of the Stars" by William Tyler Olcott . This simple book, first published in 1907, has plenty of very easy to read charts. Olcott concentrated on what can be observed as opposed to many of the theories that abounded about the cosmos, and it looks as if the charts were custom made for e-readers. One thing I have noticed is that these charts are not centered properly on the Nook; they are off to the right, but fortunately still quite usable.
Another, even older, book is Garret P. Serviss' "Astronomy With An Opera Glass" , initially written in 1888. Much like Olcott, the concentration is on what can be seen modestly, in this case with the smallest of optical instruments available, the opera glass. Like the later Olcott, Serviss does not go much into the theories of the period but instead concentrates on the stars and constellations themselves. My only complaint is that the charts are done white on black. On the Nook, they look fine though a little dark. They turn out smaller on the Kindle, but you can zoom in on them; the Kindle even rotates them to better fit the screen.
There are no doubt other ways to use e-ink e-readers in the field, and these are really just a few suggestions. Give it a shot, lighten your load and go lower tech on your next night out.