Goto Alignment

The specs of today's go-to scopes are impressive. The HC "library" contains tens of thousands of distant deep space objects, it knows the details of all of them, and it knows where each is located in the sky. That's pretty smart, huh? Nope. Computerized scopes are actually very dumb. They do not know a thing about the sky until you tell them. You tell them by entering time, date, location, and position information and by pointing them at two or three bright "alignment stars." These stars allow the telescope computer to develop a "model" of the sky in its pea brain (Figure 3). Once that is done, the CAT will impress, reliably pointing at those thousands of objects. Remember, though, that it can only do that accurately if it has been given accurate working information. For good go-to results, be scrupulous about entering data correctly and, even more important, doing a good job of centering alignment stars.

To get started, flip the telescope's on-off switch to on and follow the instructions in the manual and on the HC just as during the fake alignment. As before, the step is often to place the telescope in home position (some Celestron scopes skip this step). During the fake alignment, a compass was used to point the telescope north if pointing north was part of the "homing" process. This time, Polaris is the north reference. A compass would work, but that is usually not a very accurate way to point to true

Aligning a Generic Go To Telescope...

3) After placing scops in fevslflnorth hom® posrtor (if required), sJignment cart begin. The Tslescops will point close to two alignment stars. Use the hand controller to center each star in th® finder and in the main tolscope.

3) After placing scops in fevslflnorth hom® posrtor (if required), sJignment cart begin. The Tslescops will point close to two alignment stars. Use the hand controller to center each star in th® finder and in the main tolscope.

Figure 3. (Go-to Alignment) The go-to alignment process, which allows the telescope computer to develop a 'model' of the sky. Credit: Author.

Figure 3. (Go-to Alignment) The go-to alignment process, which allows the telescope computer to develop a 'model' of the sky. Credit: Author.

north. In many areas, true north, what the scope wants, and "magnetic north," what a compass shows, differ. If Polaris can be seen, aiming north is easy. Undo the locks on the mount and point the scope at Polaris, centering it in the finder. Then, lock the RA/azimuth lock, level the tube using a bubble level if leveling is required, and lock the declination/altitude lock. Double-check that both locks are firmly in place before proceeding. Remember, the telescope cannot move under computer control unless both locks are firm.

Enter time, date, latitude, longitude, and any other required data as instructed by the HC and the telescope manual. If the telescope is equipped with a global positioning system (GPS), it will enter most of the data itself. The telescope should be able to determine time, date, and geographic position from GPS satellites if it can get a "fix." Most GPS scopes will not set the time zone or daylight savings time status, so double-check these entries. Some non-GPS Meade scopes, the LNT models, retain and update date and time from session to session and will not require these data to be entered every time the scope is used unless it has been moved to a new time zone or a geographic location greater than about 60 miles from the previous one.

It is time for the telescope to point at its go-to alignment stars. Select the alignment mode that allows the scope to choose its own stars ("Easy," "Auto," etc.) and push the "go" button—"Enter" or "Align," depending on the scope model—to begin. If you want to try SkyAlign, that is fine. Just be sure to follow the manual's "rules" for star/object selection carefully. The Celestron scopes' two-star mode seems to be a little quicker the first time out. The motors will hum (or grind), and the tube will slew to the place where it thinks the first alignment star ought to be. This is when novices often freak out. Usually, the telescope will stop at a spot considerably distant from the specified star. Even with the tripod precisely leveled, the scope accurately placed in home position, and all data entered correctly, it is almost certain that the chosen star will not be visible in the telescope's eyepiece. It may not even be in the finder scope. What happens now? Is it time to give up and start over? Is it time to call the dealer?

If the telescope stops half a sky away from the correct star or does something wacky like pointing at the ground, something is obviously wrong. Check the setup procedure in the manual and the troubleshooting tips in this chapter. If, however, the scope stops only a relatively short distance from the first alignment star—say, one or two fists' widths when a fist is held at arm's length (10 to 20 degrees)—the telescope is probably okay. Just move the star into the center of the finder's field using the direction buttons on the HC and center it in the main eyepiece. If the HC moves the scope too quickly or too slowly, adjust slewing speed by following the instructions in the manual.

If you are a new astronomer and not overly familiar with the sky, there may be one other big monkey wrench thrown into the go-to alignment business: How do you know whether you are centering the correct star? When the telescope stops moving, there will probably be quite a few stars visible in the finder. Some astronomy old-timers will suggest you stop, get a chart, and begin to learn the bright stars. That is not a bad idea since knowing which star is which is handy knowledge to have. You do not have to sit down and learn all those stars right now, though. Here is a trick: Alignment stars are always bright. Use the brightest one closest to the place where the scope stopped.

Center the first star as precisely as possible. You probably should use a mediumpower crosshair reticle eyepiece (available from most scope dealers). When the first alignment star is dead center in the ocular, move on to the second one by pressing Align or Enter as required. Center star number two and press the button that accepts it. If everything has gone well, the HC will think for a while (sometimes for minute or more) and display "Alignment Successful" (unless it is a GEM, in which case it may need several more alignment stars first). What if it says "Alignment Failed"? Most of the time, it is not the scope, it is the operator; usually, needed data have been entered incorrectly. Power the scope off and start all over again. If it turns out it was "pilot error" and not the fault of the scope, do not beat yourself up. If you still do not get that "successful" message, proceed to the troubleshooting section. Otherwise, try a go-to or two.

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