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Last updated: 31 July 2011
This page is for user comments on Astronomy software for the Windows (including the Meade AutoStar Suite), Macintosh, Android, and iOS systems. Items that are more "review" oriented will be posted on the Astronomy Software Reviews page. If you have any comments, suggestions, questions or answers to questions posed here, e-mail them to me for posting. Please use an appropriate Subject Line on your message per the Site Email Etiquette. Thanks. Remember, tips described on this site may invalidate the warranty on your telescope or accessories. Neither the submitter nor myself are responsible for any damage caused by using any contributed tips.

Subject:	Guiding an ETX 80
Sent:	Saturday, July 30, 2011 13:50:20
From:	Mark Stewart (
I have an ETX 80 I have modified with roller bearings in the RA base. It
now operates smoothly in polar mode. There is a good bit of PE in the
worm/worm gear. Is it possible to use phd guiding to guide the ETX 80?
Is there a source of a new worm ring gear?

Thanks Mark
Mike here: With the proper serial cable (a #506) and a reliable RS-232 serial port, you would think you should be able to guide using software. Just set the software for an ETX with AutoStar #497. How accurate the guiding would be might be a question though. As to replacement gears, see the articles "Replacement Gears source" and "Gearbox Replacement" on the Helpful Information: Telescope Tech Tips page.


I have the 494. I have tried using phd guiding but the scope seems to
over respond to the guide commands. I used the ascom chooser fort the
497 and it seems to communicate fir. I adjust the slew spped to 2x the
lowest I could choose and it helps a little. It seems the trouble is
inthe backlash compensation set when training drives. Can this be turned
off? I had checked out those two articles mentioned but they are aimed
at the 105 and 90 which are fairly different.

Mike here: The articles I mentioned were just a possible source for gears, not HOW to replace them on the telescope. It may be that the software is not sending the proper the commands to the #494 or that the #494 is not responding the same as a #497. Perhaps Dick Seymour knows more about PHD.


From:	richard seymour (
What version of firmware is in the 494?  (setup/statistics/enter/scroll

Also, which version of ASCOM?  (or the 497 driver, to be specific...
it's shown on the driver's Properties or Setup page)

By choosing a speed greater than 1 you are engaging the Autostar's
anti-backlash routines
(if you are Polar mounted, the DEC axis *always* has anti-backlash
You can lower the effect of gear reversals by lowering the percentage
Setup->Telescope->Az/RA percent    and  Setup->Telescope->Alt/DEC percent

Those values tell the Autostar how much of the Train Drive results to
apply as a "quick spin" when the motors are reversed.

IF you were in speed 1 (which is 67% of sidereal), then an East guide
command would only *slow* the RA motor, not reverse it.
But at speed 2 (2x sidereal) an East guide command *does* reverse it,
and the anti-backlash compensation kicks in.  Then, when the guide
command is removed, the motor reverses *again* to resume westward
sidereal motion.

The 497 Autostar understands "pulse guiding"  (:Mge123#) commands, the
older 494 firmware does not.
I'm pretty sure the ASCOM driver does not try to "pulse guide" a 494
(i'll check).
Therefore the ASCOM driver merely issues "motion" commands, which will
operate at whatever slew speed the Autostar is set for.
I would expect that the ASCOM driver attempts to lower the speed to
Guide at some point, and (like Meade's Autostar Suite) it may
repetitively send that command to guarantee that the speed remains slow.
 But it may only lower the speed *once*, which is why your manual speed
changes help. ASCOM programming usually expects that you are doing all
command functions through the serial channel, and are not tapping
buttons on the handcontrol at the same time.

have fun

And more:

Hi... (both responses joined here)

 > Autostar version 13Ed

That's newer than any version i've seen.
If you use hyperterminal (for example) you can send something like 
:Mgn8000# to it and see if it moves north at guide speed for eight
Method of using hyperterminal:

(sending it :Mn#  will start it moving north at the currently selected
slew speed,
  and :Q#  should stop it)

 > Ascom driver 5.0.2 Meade Classic and Autostar I

I've been reading the ASCOM driver source.
They do lump the 494 in with the 495, and they do assume it can "pulse
I don't remember if i've tried that or not (my 494 is v12Ea).
I'll try to give it a shot and see if it's willing.

If they are *not* using pulse guide (which has "move at guide speed"
inherent in the command), then they are sending  :RG# :Md# (pause) :Qd#
In place of "d" they're sending the direction (n/s/e/w).
The ":RG#" is supposed to be kicking the Autostar to speed 1 (guide).
So that should override any keypad-set speed request.

 > I will play around with the settings next chance I get. I was hoping
 > that someone had already guided an ETX80 and had a rough idea of what
   settings to use.

I know of no one else who attempts to "guide" an ETX80, and i'd suspect
that anyone who did would've upgraded to a 497 Autostar.

...keep reading...

On 7/31/2011 11:19 AM, Mark Stewart wrote:
>    Thanks for the info. I will try adjusting some of the settings next
> chance I get. I don't have a 497  but I notice the newest ascom driver
 >  Meade Classic and Autostar I has  a checkbox to "use newer
> pulse guiding". Does this work with the 494?

You'll have to run tests on yours.  I'll run tests on mine, but yours is

> The PE I measured seems to vary with the position
> on the worm wheel rather than the worm, hence my desire to change the
> wheel gear. Does
> anybody know the period of rotation of the worm in seconds?

How many teeth are on the final RA driven (by the worm) gear?
Since it has to pass that many teeth (worm rotations) in a 24 hour day,
just divide 24 hours by the number of teeth to get one worm rotation's

Digging thru Mike's site, there are many "repair an ETX60/70/80" pages
from his Tech Tips page.
One (the Google translation of "ETX-80 AXIS REPAIR") had a good photo of
the drive gear, and i see that it has 96 teeth.
24 hours = 1440 minutes / 96 teeth = 15 minutes per worm rotation, or
900 seconds
(not correcting for sidereal... that would be 23h 56m = 1436 min / 96 =
897.5 seconds)

have fun

Subject:	A Problem connecting Autostar to PC
Sent:	Thursday, July 21, 2011 01:49:04
From:	Arya Ghavamian (
I hope you are doing well. I have a problem connecting AutoStar (#497)
to PC. I also use the USB adapter. I am using Win 7 64 bit. When I want
to connect the HandBox to the PC the AutoStar software delivers
"connection attempt failed"
I appreciate your help.

Thank you, and thanks for your great website.
Mike here: I assume you are using the current AutoStar Update application version 5.9 (or later). If you don't have that version, get it from Meade's web site. Also, not all USB-serial adapters work reliably with the AutoStar. Which adapter do you have? See the article "AutoStar and USB" on the Helpful Information: AutoStar Info page for more info.
Subject:	re: etx question
Sent:	Wednesday, July 6, 2011 21:43:08
From:	richard seymour (
For fully flexible remote control, the 497 Autostar allows you to change
the firmware programming itself (which may help with your goals).  You
will find firmware "patch kits" linked from Mike's Autostar Info  page.

For most astronomical applications, the 494 Autostar *is* adequate.

It *is* possible to build your own 506 cable adapter, visit:
for details.

have fun

P.S. I just noticed what your application is.

Among the patches to the 497 firmware is the ability to control the
slewing speed of each axis of the telescope independently (so you can
pan in azimuth at one speed, and track in elevation at a different
speed).  The patch kit gives it the :RA and :RE commands listed in
Meade's command document.


From:	Dmitry Bershadsky (
Thanks for the help guys.  I'm going to try it out pretty soon, just got
the cable in.

Subject:	etx question
Sent:	Friday, July 1, 2011 08:50:49
From:	Dmitry Bershadsky (
I've been poking around your site and I just want to make sure I have
this right.  I'd like to write some PC software to control an ETX-70. 
It seems that I won't be able to build my own cable and I have to
purchase a MEADE #506 catalog #04513.  Do I have this right?

Also, do you know where I can find information on the serial protocol to
talk to it?  I see a document on your site about the LX200GPS/Autostar
II but I can't find anything specifically for the 70. seems to
imply a set of commands for "all" telescopes.. but I'd rather get your
confirmation before investing in the cable.
Thanks in advance!
Mike here: For the AutoStar #494 (that is standard with the ETX-70) you do need a #506 serial cable (which is not easily made). Alternatively, you can get an AutoStar #497, which is more capable and uses the #505 serial cable (easily made). Remember, that you will need a RS-232 serial port on your computer. If you have only USB, then you will need a USB-serial adapter. But not all adapters work reliably with the AutoStar; see the article "AutoStar and USB" on the Helpful Information: AutoStar Info page. Also on the AutoStar Info page are four articles discussing programming "commands" for the AutoStar.


Thanks for your quick reply.  The #494 and serial should work for my
purposes.  I'm adapting the scope to track a UAV helicopter so I
probably won't need whatever upgrades there are between the two Autostar
versions. The idea is to mount two cameras on the scope and use it for
close up and wide angle video during test flights.

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