Even those novices who agree that running a go-to scope from a laptop sounds downright cool become a little skittish when it comes to hardware. Doesn't astronomy software require a powerful computer? What effect is dew going to have on an expensive laptop? Will low nighttime temperatures send a brand new Dell to hell Isn't that nice, bright LCD screen going to ruin the dark adaptation of everybody on the observing field? How complicated is interfacing a scope to a PC?
Truth is, almost all astronomy software is less demanding of computer resources than the PC games the kids (and maybe you) play. Even the most advanced astro-ware doesn't need much horsepower; it pales in comparison to something like Doom. There are laptops on the market today able to handle the most graphics intensive astro-ware selling for $400. If beautiful graphics aren't important, a five-year-old used computer will be more than adequate. Basic astronomy program functions such as drawing star maps, identifying objects, and sending the SCT on go-tos are far less demanding than building the 3-D world of The Sims. How about desktops? You should avoid using one of these at the scope for two reasons: safety and convenience. Since a desktop needs 110vac to operate and is designed for use indoors in a dry environment, exposing one to dew isn't smart or safe. Convenience? It's just too much of a pain to lug out monitor, keyboard, and system unit for each observing session.
Won't dew do-in a laptop? Don't worry too much about it. Most laptop computers generate enough internal heat to keep them dry under the dampest conditions. Or build a simple enclosure to protect the PC (Plate 61) using, perhaps, lightweight vinyl sign material. This is the stuff politicians use for those annoying yard signs at election time and is available in easily cut sheets online for modest prices. Fasten the sheets together with strips of self-adhesive Velcro so your laptop enclosure stores flat for easy transport. Even cheaper and locally available is foam-core board (sold in craft stores), which is composed of a thin sheet of Styrofoam-like plastic sandwiched between two sheets of poster paper. Seal the paper with a can of spray stuff from the same craft store, strengthen it along the edges with some half-round molding from a home improvement place, and put it together with—what else?—duct tape. You can also store in this enclosure eyepieces and other small items during an evening's observing run in order to keep them dew-free.
Low temperaturesare usually not any more of a problem than dew. Again, the computer generates enough heat internally to keep it happy. Under truly bitter conditions some laptop displays, especially those on older machines, may become slow and unresponsive, not unlike hand controller displays. Kendrick makes a dew heater for laptop screens for use with their heater controllers that should keep the PC usable under harsh conditions. Although this heating pad affair is surprisingly expensive, at $155, it may be a godsend for laptop users in the frozen north.
Plate 61. (Computer Enclosure) Corrugated plastic sign material is perfect for building a simple laptop enclosure. Credit: Author.
Most astronomy programs feature a night-vision mode that turns the Windows (or Mac) screen colors to shades of red and black. Invoke that, turn down the laptop's display brightness to a low setting, and the screen may be dim enough to preserve night vision—but probably not. Usually some element, often the taskbar in Windows, will be left white and will be too bright no matter how the display is adjusted. Most observers solve this problem by using a material called "Rubylith," which is a transparent red film used in the graphics/printing industry. It's commonly available at graphics/art suppliers but, increasingly, can be obtained from astronomy dealers due to the popularity of laptops for use at the scope. Cut a piece to fit the screen, either tape it down along the edges or just let static cling hold it in place, and the laptop's display will be more than red enough and dim enough.
The laptop is snug in its little enclosure and its screen is red and dim. All that remains is the physical act of hooking PC to go-to. Unless the telescope is a Meade RCX400, that means buying or making a serial cable in the proper format for the scope and plugging it into the laptop's and mount's serial ports. As mentioned previously, most modern laptops do not possess serial ports. The usual solution is a USB-serial adapter. Yes, I discourage the use of these little cables earlier, but most of the time they do work OK for simple tasks such as sending a scope on go-tos from the PC. It's also true that some USB serial cords work better with scopes than others. If trouble is encountered the easiest solution may be to buy an adapter from Meade or Celestron. Both companies sell them, and there should be no question that they will work with their scopes.
What kind of serial cable is needed to hook the laptop to the scope? Not the standard RS-232 serial cables; the right kind can be purchased from most telescope dealers. Can't spend for yet another CAT accessory? These cords are nothing fancy and aren't hard for experienced electronics tinkerers to make. For instructions on building Celestron cables see Michael Swanson's excellent "NexStar Resource Site." For Meades, have a look at Mike Weasner's famous "Mighty ETX Site" (Appendix 2). Serial cables are available in various lengths, but you should probably choose a good long one, at least 12 feet. There won't be any trouble with the serial data signal getting weak or corrupted with this relatively short run, and a 12-foot length will allow the laptop to be positioned a convenient distance from the scope.
What does the serial cable plug into on the scope end? Celestrons have a port labeled "PC," but, as discussed in the Buyer's Guide chapter, that's not where the laptop cable goes. It goes into a small RJ-style receptacle on the base of the hand controller. Same with some Meades; there's a plug called "Aux" on their mounts that sounds like it might accept computer input, but that is exactly where not to plug in the laptop. Instead, as with Celestron, the serial cable goes into an RJ receptacle on the Autostar hand controller. Some Meade scopes feature RS-232 connectors on their drive bases as well.
Astronomy software has come a long way over the last twenty years. The typical program now offers millions of stars, hundreds of thousands of deep sky objects, and (sometimes) a photo-realistic depiction of the sky. Astro-ware has also branched out into a couple of different "genres." You wouldn't use Microsoft Excel to write a letter (though you could), and you also wouldn't use a planetarium program to plan a night's observing (though you could). Astronomy software comes in two distinct flavors now, planetariums and planners.
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