for PC to
Scope Communication Problems
Laptops in particular can be a little tricky with the serial port.
NexStar Observer List (NSOL) uses the most straight-forward method possible
for communicating via the serial port, so if you are having problems with
NSOL, other programs will experience the same problem. If you can get
NSOL working, but not your other programs, visit their web site for any
updates and/or contact their technical support. Here are some things
to try to get your PC and scope communicating:
- The telescope must be aligned before it will accept commands. To test
indoors, simply perform a Quick Align or an Auto Align, accepting the
locations pointed out for the two stars.
- NSOL and almost all other astronomy programs can only communicate with
the telescope via the port on the bottom of the hand control - not the ports
on the base of the mount.
- Perhaps you selected the wrong telescope type in the program; you will
not harm your telescope or computer testing other scope types.
- Some combinations of computers and NexStar telescopes are sensitive to
the order of events when connecting the two. Try aligning the scope with the
PC disconnected from the hand control. Then connect the PC and start your
- For some models of NexStar (N5/8 and the new version of the
N60/76/80/102/114/4/130), you must enter 'RS-232' mode from the hand control menu
before the scope will accept commands.
- Be sure there are no other programs using the serial port. For
example, installing older Palm Pilot software on a computer is a sure way to
disable the serial port for access by other programs like NSOL. If there is
a little icon for synchronizing in the system tray (the section in the lower
right corner of the screen with the current time), then you can be pretty
sure that a synchronizing program has taken control of the serial port. You
can generally close such programs by right-clicking the icon in the system
tray and choosing exit. If you no longer use that program, try removing it
with Add/Remove Programs in the Control Panel. Desktop PCs do not
generally have much problem with conflicting comm ports, EXCEPT in
the case of software to synchronize a PDA such as a Palm Pilot.
- Try other 'Comm Port' settings. In NSOL comm port settings are found
in the Tools, Setup menu.
- Go to Control Panel (Start menu, Settings) and open the System icon.
Click on the Device Manager and look for 'Ports (COM & LPT)'. There should
be a '+' mark next to it and when you click the +, Device Manager will
expand to show the actual ports. At least one of the ports should be labeled
'Communications Port (Com1)' or perhaps Com2 or other. If the little icon
next to this entry has an X through it, you must double-click the icon and
try to determine why the comm port is not operating.
- If you are using a USB to serial adapter, you may not have
loaded the drivers when you first plugged it into your computer.
Follow the directions in the step above to open the Device Manager.
Plug the adapter into your computer - this should cause a comm port
to appear in the Ports section. Unplugging the adapter should cause
it to disappear from the Ports section. If instead it creates a
large yellow question mark icon, right-click that icon and remove
it. Then locate the CD that came with your USB to serial adapter,
put it in the CD drive of our computer, plug in the adapter again
and follow the on screen directions to install the driver. If you
can't find the CD, try to locate the driver on the adapter
manufacturer's web site.
- If you are using a USB to serial adapter, it must provide a true
serial port. Some adapters are HID - such adapters are
designed for "human interface devices" only, in other words, you can
connect a mouse to such an adapter but not a telescope.
- If you are using a USB to serial adapter and have exhausted all
attempts to make it work, a PC Card is a better solution if your
laptop has a PC Card slot. Most computer stores stock the USB
to serial adapters but the PC Card can be hard to find in a local
here for Google results for RS-232 PC Cards. The newest
laptops now have an ExpressCard slot rather than PC Card slot. Click
for Google results for RS-232 ExpressCards.
- Another potential conflict with a laptop computer is an infrared (or
IrDA) port. You can find that listed in the Device Manager as well. If you
are not using the infrared port, double-click the icon (not the one with the
+ mark, but rather the one below it) and check the box to 'Disable in this
- A faulty cable might be the problem. One way to test the cable
is to install NSOL on a standard desktop PC and try controlling the
scope from there (remember the indoors alignment from number 1
above). Also, be sure it is for NexStar telescopes. For
example, the control cable for Meade telescopes appears to be
identical but the pin connections are different and the cable will
not work on NexStar telescopes.
- Take a good look at the connector on the bottom of the hand control -
insure none of the pins appear bent or misaligned.
- There is a known problem with the serial port on many Dell
laptop/notebook computers (and some other manufacturer's equipment as well). Sometimes they will communicate with the scope,
sometimes they just won't. If you have tried all of the above and get no
communication or intermittent communication, purchase a USB to serial port
adapter and use that rather than the built-in serial port. Belkin adapters
are widely available and very reliable. Also, check with Dell, reportedly a
BIOS update that might fix the problem on some computer models is now
Most other potential solutions require investigating and possibly
changing settings for serial and/or IrDA ports in the computer's setup (BIOS
settings). This requires reasonable experience in configuring computers and
is not recommended for those not already familiar with such procedures.
Hopefully one of these tips will resolve any issue you have.