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We don't usually recommend this alignment method. But if your mount
is already well polar aligned, this option may provide accurate enough
pointing and tracking with no further alignment required. It can also be
handy when you are searching for planets in twilight.
EQ North Align and EQ South Align
(AZ mounts only)
If you are using an AZ mount on an equatorial wedge, choose "EQ North
Align" in the Northern Hemisphere or "EQ South Align" in the Southern
Hemisphere. Follow the steps for Auto Align described above, but now
consider your telescope an EQ mount instead of an AZ mount.
Center Calibration
Center calibration aligns SSAG's fi eld of view with that of your telescope.
You'll generally only need to center-calibrate the fi rst time you use SSAG
with a new telescope tube. However, you may need to center-calibrate
again if you remove the bracket base from the telescope and then reinstall
the bracket. If you only remove SSAG and its bracket, leaving the bracket
base on the telescope, you should not need to center-calibrate again.
Before doing a center calibration, align the telescope to the night sky
using one of the above procedures. If you have not center-calibrated
previously, SSAG will automatically initiate a center calibration after sky
alignment.
To perform a center calibration:
1. Press the MENU button and use the SCROLL keys to select "SSAG."
Press ENTER. Use the SCROLL keys to select "Center Calibrate" and
press ENTER.
NOTE: If you have never center-calibrated SSAG, the NexStar+ hand
control will automatically start the center calibration process after
alignment.
2. Next, use the SCROLL keys to select either Named Stars or Solar
System Objects (i.e., planets) to use for center calibration. Press
ENTER. Scroll through the list of stars or planets and select one
clearly visible from your location. Press ENTER.
• If you are unsure where the object you chose is in the night sky,
don't worry. The telescope will point close to the object in the next
step. You can use the telescope as a guide to determine which star
or planet you are using to center-calibrate. Remember that named
stars and planets are among the brightest objects in the night sky.
• For best results with an EQ mount, choose stars that are close to the
celestial equator (i.e., away from poles).
3. The telescope will slew to the star or planet you chose. Depending
on the offset between SSAG's fi eld of view and the telescope's, the
object may or may not be in the telescope's fi eld of view. In any case,
the telescope should generally be pointing toward the object.
4. The NexStar+ hand control will ask you to center the object in the fi eld
of view of the fi nderscope. Use the direction buttons on the keypad
to do this. Don't worry about fi ne centering yet—that happens in the
next step. For now, roughly center the object in the fi eld of view of the
fi nderscope and press ENTER.
• If the star is not within the fi nderscope's fi eld of view, slew the
telescope manually until it is.
• If you're not using a fi nderscope, use your widest fi eld eyepiece in
the telescope for this step. If the object is not in the fi eld of view,
try sighting down the length of the telescope tube to point to the
object.
5. The NexStar+ hand control will prompt you to center the object in
the eyepiece's fi eld of view. This is the fi ne-centering step. Make sure
there is a high-powered eyepiece in the telescope. Use the direction
buttons on the keypad to center the object. For the best results, use
the up and right direction keys last. When you fi nish, press ALIGN.
6. SSAG will perform the center calibration and return the message
"Center Calib Success."
Once you've completed Auto Align and Center Calibration, you can
command the telescope to accurately place any celestial object you
choose within the telescope's fi eld of view.
Autoguiding
If you are imaging an object with a camera, you can use SSAG to
accurately autoguide the telescope through the exposure.
After you complete the alignment and center calibration, you can initiate
autoguiding by pressing the MENU button and using the SCROLL keys
to select "SSAG." Press ENTER. Then use the SCROLL keys to choose
"Guiding" and press ENTER.
The hand control's LCD will display a screen like Fig. 12. The numbers
on the top line represent the right ascension (RA) RMS tracking error,
and the numbers on the bottom line represent the declination (Dec) RMS
tracking error in arcseconds. The +/- symbols to the right of the RA and
Dec RMS tracking errors indicate the direction of the previous tracking
command on that axis. The "s" number is the number of stars SSAG is
using for guiding. The "Q" number represents the quality of the guiding,
which is essentially a measurement of the local seeing conditions—zero
is poor while 100 is ideal. The blinking asterisk next to the Q number
indicates that the hand control is receiving guiding commands from
SSAG.
SSAG will continue guiding indefi nitely. When you are ready to stop
guiding, press the BACK button. (While autoguiding, none of the hand
control's buttons will work except the BACK button.)
Fig. 12: While autoguiding with the NexStar+ hand control, you'll see the guiding
error for both axes on the LCD.
Polar Alignment
Although your equatorial mount does not need to be accurately polar
aligned to use SSAG, SSAG can help you achieve a very accurate polar
alignment. A precise polar alignment slightly improves overall pointing
accuracy—but only by a few arcminutes. If you choose to polar align, do
so before sky alignment and center calibration. Keep in mind that only
equatorial mounts or AZ mounts using EQ wedges can be polar aligned.
NOTE: These instructions explain how to perform the polar alignment
procedure in the Northern Hemisphere. If you are in the Southern
Hemisphere, always point your mount due South instead of due
North.
To perform a polar alignment with SSAG:
1. Roughly polar aligning your mount fi rst will make the entire process
quicker and easier. Once you are roughly aligned, you can achieve an
accurate polar alignment using only the mount's altitude and azimuth
fi ne adjustment knobs.
a. Make sure the mount is reasonably level. If your mount has a
bubble level built in, use that for reference.
b. Adjust the altitude of the mount so that the mount's latitude scale
indicates roughly the same latitude as your observing site.
c. Lift and rotate the entire tripod and mount so that the right
ascension (RA) axis points approximately due North. The
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