Retrofitting Autostar GOTO control to the Vixen SP and GP style

Retrofitting Autostar GOTO control to the
Vixen SP and GP style GEM mounts using
Meade DS-Series motors.
Vixen SP, SP-DX, GP, GP-E, GP-DX
Celestron CG-5
Synta EQ-4, EQ-5
Skywatcher EQ-4, EQ-5
Orion SkyView Pro
Jinghua HD (Apogee Inc.)
Version 1.2 - 2/14/03
Official source for this document and all updates - www.data-plumber.com
Official discussion group - http://groups.yahoo.com/group/RoboScope
Make sure you have the latest version of this document!
By
Christopher Erickson
Anchorage, Alaska, USA
[email protected]
With invaluable contributions made by:
Mike Weasner, http://www.weasner.com
Steve Bedair, http://www.bedair.org
Dick Seymour, [email protected]
Hans Peter Wallner, http://members.aon.at/wallnerstelescopes
Tom Duggan, http://www.tomduggan.com
1
INTRODUCTION
This document is a (hopefully) complete set of construction plans for retrofitting a Meade Autostar GOTO handheld
computer and motors from a Meade DS-Series telescope or the #493 or #492 accessory motor kit to a Vixen or Vixenstyle German Equatorial Mount (GEM).
The Meade Autostar GOTO telescope control system has proven to the most popular and versatile system of its kind to
date. Meade has put their Autostar system on about 25 different scope models so far and the future looks strong for
the Autostar.
Until the release of the Meade LXD-55 series, Meade did not have a mid-sized GEM mount combined with Autostar
control. I don't count the 4504 and 114eq-dh4 because those mounts are so light. Many owners of the venerable
Vixen-design GEM mount had to go with the expensive, limited, quirky, non-intuitive and poorly-supported Vixen
SkySensor-2000 system.
That all changed with the release of the Meade DS-Series of small telescopes with optional external axis motors. It
turned out that these motors could be attached to the worm shafts of other telescopes and the ratios of those worms
could be programmed into the Autostar. Wow!
I am making this document freely-available. I only ask that it not be modified and redistributed without my knowledge
and prior approval. I would prefer that suggestions and changes are submitted to me for inclusion in future revisions of
this document. Appropriate credits to contributors will be included.
Discussion on gear ratios
It is the fact that Meade made the gear ratios programmable instead
of fixed in the Autostar that we can retrofit the Autostar to nonMeade telescope mounts. Meade even went so far as to make it
possible to input negative ratios and drive the motors in the opposite
direction from their telescope models! Thanks, Meade.
Here is a table of common worm gear ratios and their appropriate
Autostar ratio numbers:
60:1 - 1.36889 (standard DS-Series telescope ratio)
90:1 - 2.05333
120:1 - 2.73778
144:1 - 3.28533 (standard Vixen GP & clone ratio)
180:1 - 4.10667 (common Losmandy worm gear ratio)
270:1 - 6.16000 (common Losmandy worm gear ratio)
359:1 - 8.19053 (common big mount worm gear ratio)
360:1 - 8.21334 (common big mount worm gear ratio)
WARNINGS AND DISCLAIMER
All power tools are dangerous and you are hereby warned to follow all manufacturer's warnings and realize that you are
accepting all risk associated with the use of power tools, hand tools, electrical equipment, electrical systems, slippery
counterweights and dangerous paper edges that might exist if you print out this documentation and take it into your
workshop!
Also be aware that there are a lot of minor variations in the mounts discussed in this document and that some latitude
should be maintained when attempting to apply the information presented here. I have made every effort to identify
and address those variations, but omissions must certainly exist. Beware!
ERRORS AND OMISSIONS
If you find any errors or omissions I ask that you take a moment to notify me so I can correct them. If you have any
suggestions on improving the quality or clarity of the information presented here, please pass them along to me. If you
come up with any improvements on the process or in any of the techniques, I would be grateful for that feedback too. 2
MEADE PARTS NEEDED
1 - Meade 495 or 497 Autostar with coiled cord.
2 - Meade DS-Series axis motors with integral coiled cords.
1 - Meade control panel (connector panel).
2 - Meade 22-tooth white gear and retaining screw.
1 - Meade #505 computer interface cable (or make your own).
SOURCES FOR THE REQUIRED MEADE PARTS
A DS-Series telescope with motors and 495/497 Autostar to be stripped and salvaged.
or
A Meade #493 motor kit with included 495 Autostar controller.
or
A Meade #492 motor and controller kit plus a separate 495/497 Autostar.
OTHER PARTS NEEDED
12VDC battery pack with automotive cigarette lighter female plug, 1.5 Amp-hour minimum.
12VDC cigarette lighter plug power cord, fused.
5.5mm barrel, 2.5mm center pin power connector, positive tip polarity.
Cellphone adhesive male and female clip set (optional, for back of Autostar).
Handheld bubble level and/or a circular bubble level.
TOOLS
Hobby Lathe*
- Sherline (small projects, best quality)*
- Taig (small projects, high quality and a great value)*
- Harbor Freight or Grizzly (Chinese import)*
- Smithy (very versatile and more expensive)*
- Prazi (very precision and more expensive)*
Compatible taper tool for selected hobby lathe*
Tailstock chuck for selected hobby lathe*
Cut off tool for selected hobby lathe*
Digital caliper (English and/or Metric, General Tools model #143 or similar)*
Band Saw (hacksaw and vise can be substituted)
1/4" or similar centering bit, a.k.a. combination bit*
6mm drill bit (1/4" drill bit can be substituted if absolutely required)*
2.5mm tap (English 4-40 tap can be substituted if 2.5mm is not available)*
6-32 tap (or near metric equivalent)*
Hex key for 2.5mm cap screw*
Hex key for 1/4" cap screw
Hex key for 6-32 set screw*
FABRICATION SUPPLIES
Aluminum rod, about 5/8" (about 15mm) by about 4" (about 100mm)*
Aluminum angle, about 1.5" by 1.5" by 1/8" (about 40mm by 40mm by 5mm)
6-32 by 1/4" set screw (or near metric equivalent) (2)*
1/4-20 by 2 1/4" hex cap screw for EQ-4/GP's (or near metric equivalent)
1/4-20 by 3" hex cap screw for CG-5/SP's (or near metric equivalent)
1/4-20 by 1 1/4" hex cap screw (or near metric equivalent)
1/4-20 Nylok style nut (2)
1" wide or similar fiberglass tape (6" tubing clamps can also be used)
Aluminum rod, about 5/8" (about 15mm) by 8" (about 100mm) for SP/CG-5 spacers.
Aluminum disc, about 4" by 1/2" (about 100mm by 15mm) for EQ-4 spacer .
* Only needed if making your own shaft adapter.
3
SHAFT ADAPTER - ORIGINAL STYLE, FULL-MACHINING APPROACH
Here is the original shaft adapter that I designed. There isn't any rocket science here and many of the dimensions are
not critical. The almost-exceptions are the 6mm hole, the tapered 6mm shaft and the 2.5mm threaded hole.
The 6-32 set screw is non-critical and a similar metric set screw would be fine.
If you cannot find a 2.5mm tap so you can re-use the Meade gear retaining screw, a 4-40 tapped hole and a 4-40 hex
head cap screw will work fine.
If you cannot find a 6mm drill bit, 1 /4" drill bit will work. It will be a bit large and the motors will undulate a bit during
fast slewing as a result. The motors will work just as well but your pride may be damaged a bit when people (or worse,
your friends) ask why the motors undulate when you are slewing the scope.
Aluminum is my favored material for the shaft adapter. Brass can be used but be careful to drill the 6mm hole first or
the 6mm bit will grab if it connects to the smaller 2.5mm tapped hole.
Stroke the tapered shaft lengthwise with a coarse grit sandpaper. That will greatly improve the grip of the plastic
Meade gear on the shaft.
The large-diameter end's length can optionally be shortened a bit for some mount variations and might have to be
longer for others. I have picked a length that I hope will be universal for all mount variations.
This page can be printed and taken to a commercial machine shop.
Hand-check the tapered tip when
cutting. Stop when the Meade gear
stops when it is about 3/8" from being
fully seated on the tapered shaft.
6-32 tapped hole
2.5° taper
15.8mm
5/8"
6mm
2.5mm tapped hole
8.9mm
0.35"
21.3mm
0.84"
25.4mm
1.0"
11.4mm
0.45"
20.3mm
0.8"
45.7mm
1.8"
4
SHAFT ADAPTER - MODIFIED STYLE, MINIMAL-MACHINING APPROACH
By using a 6mm by 25mm shaft coupling with integral set screws, a good deal of machining can be avoided. The
problem is that I have yet to find such a beast. If anyone finds one, please let me know!
A 1/4" by 1" shaft coupling would work as well.
The trick here is to cut off the last portion of the Meade brass worm shaft and to mount it in one end of the shaft
coupling. The other end will go on the mount's existing worm shaft.
This page can be printed and taken to a commercial machine shop.
6-32 tapped hole
(or similar)
6-32 tapped hole
(or similar)
Meade brass shaft piece
16mm
6mm
(approx)
24mm
(approx)
25.4mm
1.0"
20.3mm
0.8"
45.7mm
1.8"
5
SHAFT ADAPTER - CREATIVE STYLE, NO-MACHINING APPROACH
By using the clutches from a Vixen, Synta or Celestron dualaxis controller system it might be possible to create a
makeshift shaft adapter that will work with some success.
The challenge will be to prevent the Meade gears from
twisting on the clutch stems without splitting the inside of the
plastic gear in the process.
I have not included parts or tools for this approach in my
equipment and supply list.
It would be good to stroke the clutch shaft lengthwise with a
coarse grit sandpaper to improve the grip of the Meade gear
on the clutch shaft.
Stock Drive Products distributes a commercial 6mm shaft
extender, part # S52FCYM060060, made by Fairloc. You
will have to taper the tip. See the URL on the Resource
page. Some people have used a drill press and a file to
hand-shape the tapered shaft. A hand drill could be used
too. I would suggest checking the gear fit frequently if you
decide to attempt this approach. With gentle finger
pressure, you want the shaft to stop about 3/8" from being
fully seated inside of the Meade gear. You will be tapping
the gear down the last 3/8" or so. If you are able to drill and
tap the end of the shaft adapter for a 2.5mm or 4-40" hexhead screw, that would be great.
Ocean State Electronics distributes a 1/4" shaft adapter
that can be used. It is not a perfect fit on the 6mm shaft, but
it can be done. You will have to taper the shaft tip. See the
URL on the Resource page. Use the same tapering
technique and optional tapping as already mentioned for the
Fairloc shaft extender.
6
MOTOR BRACKET
The motor brackets are not that critical in detail specification. Variations in material dimension, thickness, length, etc.
are very flexible. I have given careful dimensions here that should prove fairly universal for most GP-style mounts.
I rough-cut the aluminum bracket using a band saw but a vise and a hacksaw could work just as well.
Cleanup was done with a coarse-tooth file.
If you want to make it pretty, you can use swirling motions with a medium-grit sandpaper for a final finish. Experiement
on some scrap first. This technique is not difficult but it takes some practice and patience.
The motors will be attached to the brackets in the final assembly by fiberglass tape. I chose fiberglass tape because of
its non-stretching characteristics.
Some people have chosen to attach the motors using large hose clamps, industrial-strength tie-wraps and even by
screws passed through the plastic motor housings.
This page can be printed and taken to a commercial machine shop.
Bottom view
32mm
1.25"
38mm
1.5"
41mm
1.6"
41mm
1.6"
1/8"
51mm
2"
Front view
38mm
1.5"
6.4mm
0.25"
41mm
1.6"
41mm
1.6"
96mm
3.8"
178mm
7"
7
WWW.GOTO4ALL.DU COMPLETE MOTOR BRACKET KITS
Stefan Konigsheim and Walter Petrick (www.goto4all.de) have done us a great service by using their manufacturing
resources in Germany to create a very professional bracket kit that makes attaching DS motors and an Autostar to GPstyle GEM mounts almost a no-brainer for anyone with a few metric Allen wrenches.
Autostar changes:
The big change is that the signs on the axis ratios have to be reversed.
Other hardware changes:
The Dec axis spacer may not be required or it may be thinner and still work well. It will depend largly on your dovetail
bracket's size and how well it clears the RA motor.
Bracket kit Included parts:
RA axis bracket
Dec axis bracket
RA axis bracket retaining bolt
Dec axis bracket retaining bolt
Two axis pulleys
Two timing belts
You will still need the DS-motors, Autostar, connector panel and a 12VDC power supply.
Required tools:
2mm Allen wrench for the 22-tooth Meade gear retaining screw
1.5mm Allen wrench for the pulley set screws
5mm Allen wrench for the bracket retraining bolts
Small flat blade screw driver for setting timing belt tension
Issues with different mounts:
I have found that my Vixen SP mount required a longer RA axis
bracket retaining bolt (70mm) and that the four pulleys had to be
reversed on their shafts as compared to other mount versions. I
also had to tap the pulleys onto the axis worm shafts with a bit
more force than what was required for the Synta and Jinghua
mounts. The axis apparently were 6.00mm instead of the about
5.95mm on the Chinese mounts.
8
POWER
The puny Meade battery packs just won't cut it here. I use a video hip-power pack
available from numerous sources. Orion Telescope and Binocular sells this pack too.
Probably any of the popular portable 12VDC power packs with the standard automotive
cigarette lighter plug connector will work. Be warned that if the battery pack is too
powerful (capable of very high amperage) there is a possibility that it might increase the
chance of motor damage from mount crashes. I suspect that the method used by the
Autostar to detect a motor stall is based on detecting a rapid slowdown in pulse
feedback from the optical motor speed sensors. If the motors can draw enough working
current, they might be able to really stress the little plastic gears before the motor slows
down enough for the Autostar to detect the mount crash and then react in time to
prevent gear damage. I am very interested in feedback from other users about this problem.
For the power cord, I use a generic one that I picked up at Radio Shack.
Many of the weird problems suffered by Autostar users are a direct result of poor power. Either low voltage (less than 9
volts), low current capability (less than 1 amp) or "dirty" (poorly-filtered and regulated AC adapters).
I place the battery pack in the tripod tray to add another tiny amount of stability to the mount.
The power cord must have a positive-tip, negative barrel polarization and the telescope-end plug has a 5.5mm barrel
and a 2.5mm center pin.
CONTROL PANEL
The control panel is another non-critical dimension component. I chose the smallest Radio Shack project box that
would hold the Meade control panel module.
The box, part number 270-1801 happens to have the same lengthwise hole spacing as the Meade module, which made
the entire job a tiny bit easier.
It is possible to mount the control box using the same 1/4-20 hex head screw that holds down the RA bracket to the
mount. The 1/4" hole will be just about centered underneath the
molded part number inside the bottom of the box. I have
superimposed a white dot in the APPROXIMATE position below
and to the right.
57mm
2.25"
28mm
1.10"
32mm
1.25"
52.9mm
2.08"
16.6mm
0.65"
9
DECLINATION AXIS SPACERS
Here are three different axis spacers. Two are variations for the SP and CG-5 style of mount and the other is for the
EQ-4 style of mount. You should double-check your mount's design and dimensions against these drawings before you
begin any metal cutting. Some people have made spacers from wood, lexan, nylon and plastic. I prefer aluminum.
The spacer is required because of the RA axis motor sticking out so far. It should not effect the operation and accuracy
of the mount.
This page can be printed and taken to a commercial machine shop.
15.8mm
5/8"
57mm
2.25"
57mm
2.25"
57mm
2.25"
SP/CG-5 Spacer, Style 1
7mm 0.28"
84.8mm, 3.34"
77.2mm, 3.04"
70mm, 2.76"
Top
63mm, 2.48"
30.6mm, 1.20"
13mm 0.51"
7mm 0.28"
Top
7mm 0.28"
41.7mm
1.64"
Side
SP/CG-5 spacer
Style 2
2.5mm, 0.1"
Side
EQ-4 spacer
12.7mm, 0.5"
10
INSTALLING THE COMPONENTS
ATTACHING THE MEADE GEARS TO THE SHAFT ADAPTERS
1. Remove the white Meade gears from the old Meade worm gear
assemblies. After removing the screws from the top with the appropriate
hex key wrench, pry the gears off with a butter knife or something. Keep
the white gears and the tiny screws, set everything else aside.
2. Place the Meade gears on top of the shaft adapters and gently tap them
down with a fist-sized piece of wood or a plastic hammer (or a butter knife
handle, shown) until they are fully seated on the shaft adapter. You will
have to verify if they are fully-seated by inspecting the shafts through the
holes on top of the Meade gears. You may have to use a magnifying
glass.
3. Once the gears are fully-seated, insert and tighten the 2.5mm screws
removed in step 1.
ATTACHING THE SHAFT ADAPTERS TO THE MOUNT
4. Now place the shaft adapters on the worm shafts of your mount and
tighten the set screws with a hex key wrench. Make sure to match the set
screw with the flat on the worm shaft. Also make sure to allow a small
amount of clearance between the base of the shaft adapter and the worm
shaft base.
5. With the OTA removed, turn both worm shafts with your fingers and the
Meade gear to verify smooth and unbinding operation. If one of the shafts
is too loose or too tight, now is the time to adjust the backlash of your
mount's worm drives. If you don't know how to do this, Vixen, Celestron
and Skywatcher have these instructions on their web sites.
ATTACHING THE MOTOR BRACKETS TO THE MOUNT
6. Now attach the RA drive bracket (both brackets are identical) using a
1/4-20 by 2 1/4" long hex head screw, a 1/4" washer and a 1/4-20 Nylok
nut with an appropriate hex key wrench and a 3/8" socket, combination or
Crescent wrench. Allow a little play to remain for now.
7. With the Dec axis facing up, Attach the other motor bracket to the
mount using a 1/4-20 by 1 1/4" screw and hardware. Allow a little play to
remain for now.
8. You will now have to remove the retaining rings from your Meade
motors using a spanner wrench or a pair of long-needle-nose pliers. You
will then remove the big spinner nuts and replace the retaining rings.
11
INSTALLING THE COMPONENTS (cont.)
ATTACHING THE MOTORS TO THE MOTOR BRACKETS
9. Now you can place the motors on the Meade gears, making sure they are
fully seated. There might be a slight angle between the motor bracket and
the mount. This is normal. When the motor is held flush and square to the
bracket, tighten the bracket screw and use fiberglass tape to secure it to the
motor bracket.
ATTACHING THE CONTROL BOX TO THE MOUNT
10. Find a place to attach the control box. This might be to the RA motor
bracket with a 1/4" hole through the back of the control box or it might be to
the tripod or wherever else you want. Velcro, double-back foam tape to the
RA Axis motor bracket's 1/4-20 bolt will work.
INSTALLING THE DEC AXIS SPACER
11. Remove the OTA and counterweight from the mount and insert the
appropriate axis spacer for your mount style. Note the two basic mount
styles. The GP/EQ-4 style mount has round Dec axis junction (see picture
below) and the SP/CG-5 style has the square Dec axis junction (see picture
at right). Tighten everything up and inspect the mount for correct, tight and
smooth operation. Replace the OTA and counterweight afterwards.
ATTACHING THE CABLES
TOGETHER
12. Attach the RA axis motor
cable to the control box's AZ
connector port.
13. Attach the Dec axis motor
cable to the control box's ALT
connector port.
14. Attach the Autostar cable to
the HBX port.
15. The AUX port would be for a focus motor if you had one.
CHECKING CLEARANCES
16. Leave the mount axis locks unlocked.
17. Move the OTA around by hand and take note of anywhere that the OTA or any brackets might crash into other parts
of the mount. Take note if the axis spacer needs to be increased to prevent the OTA and its brackets from hitting the
RA motor and bracket.
POWERING UP FOR THE FIRST TIME
You are now ready to connect power to your mount for the first time. LEAVE BOTH AXIS CLUTCHES/LOCKS
DISENGAGED FOR NOW. This will prevent mount crashes while you become familiar with the Autostar.
You are now ready to plug your clean, quality, negative ground 12VDC power source into the Autostar control panel's
"12V" power port.
12
POWERING UP FOR THE FIRST TIME (cont.)
If all goes well, you will hear a beep and then see the message "(c) nn Meade[nnx] AUTOSTAR" and then
"initializing..." and finally a warning message about not looking at the sun will begin scrolling across the screen. The
message will tell you to press a particular key to confirm that you have read the message and understand what it is
telling you. Go ahead and press the specified key if you understand the warning. If you don't understand the sun
warning, turn everything off and put everything in a big box until you do understand the sun warning.
After pressing the specified key, a "Getting Started" message will begin scrolling across the screen. After reading it,
press [ENTER] to continue.
Enter the correct date using the number and arrow keys and press [ENTER] when you are done.
Now enter the correct time for your location (this isn't real critical for testing purposes, since the time is not preserved
between power cycles).
Enter the correct Daylight Savings time mode and press [ENTER]. "Yes" for summertime and "No" for wintertime.
Assuming your location uses daylight savings time in the summer. If it does not, then your Daylight Savings time mode
should always be "No".
Now you will be prompted for "Country/State". Scroll up or down using the up/down buttons on the bottom of the
Autostar keypad to get to your country/state and press [ENTER} when you find it. Note that the menu selections are
circular. Scrolling past "Z" will take you back to the "A"'s, etc.
Now scroll to the "Nearest City" using the same technique as above. Press [ENTER] when you find it.
Now select "Telescope Model" If you have patched your Autostar firmware then scroll and select "114EQ" and press
[ENTER}. If you have not yet patched your Autostar firmware or if you only plan to use Alt-Az configuration with your
mount, select "DS-127" and press [ENTER].
At this point the Autostar should say "Align: Easy". Because we need to override the worm gear ratios for our nonMeade mount, we need to go back and make a some changes before we are ready to start driving the mount around.
Press [MODE] to escape from the "Align: Easy". Note that the [MODE] button can be generally thought of as the
[ESCAPE] button.
Press the "down" button at the bottom of the Autostar keypad until "Telescope" appears in the display and then press
[ENTER].
Scroll until "Alt/Dec Ratio" appears in the screen and then press [ENTER].
Press the left-slew button in the upper-half of the Autostar keypad. The flashing cursor should move to the left and now
be flashing on the "+" symbol in the display. Now press the "down" button once. The "+" should now be a "-". Now
press the right-slew button once. The cursor should now be back on the most significant digit of the displayed number.
Now type in 0328533. The display should show "-03.28533". Press [ENTER] when you are done.
Scroll until "Az/RA Ratio" appears in the screen and then press [ENTER].
Now type in 0328533. The display should show "+03.28533. Press [ENTER] when you are done.
Later you will do the "Train Drive" procedure but it is not important right now. "Training the drives" really means
"informing the Autostar about axis backlash". It tells the Autostar how much gear backlash (slop) exists in each axis.
The Autostar will attempt to compensate for backlash when pointing at objects. The better job you do when "training
the drives" the better your GOTO and tracking precision will be. However you DO want to perform the "Calibrate
Motor" step. This is a critical step that will prevent many problems later. This step adjusts the motor feedback sensor.
There are a lot of other settings you can fiddle with in the Autostar but none of them are important for now.
13
POWERING UP FOR THE FIRST TIME (cont.)
Congratulations for making it this far! Now it is time to learn a little bit about the Autostar GOTO computer system.
AUTOSTAR FAMILIARIZATION
The Autostar retrofit works very similar to the Meade LXD-55 GOTO mount and Meade's instructions for the LXD-55
will apply directly to this project.
The Autostar is a self-contained, handheld computer that has been dedicated to GOTO control of Meade telescopes. It
is versatile and rather user-friendly, considering its limited keyboard and screen. It can be connected to and controlled
by a personal computer, but this is not required for field operation and it is certainly
not required to effectively locate lots of interesting celestial objects by name, since
the Autostar can do all of that and a lot more without the help of a more powerful PC.
Here are some important information sources on the Autostar. I encourage you to
read through them while familiarizing yourself with your Autostar. I would advise that
you leave both axis clutches/locks unlocked for now to avoid mount crashes.
http://www.meade.com/catalog/autostar/497_autostar.html
http://www.meade.com/manuals/autostar/index.html
http://www.meade.com/support/auto.html
http://www.meade.com/support/etxautofaq.html
IMPORTANT AUTOSTAR SETTINGS:
Site - (your viewing location, saved in NVRAM) __________________________
Date - (current date, last entry saved in NVRAM)
Time - (current time, lost at every power-off, NOT saved in NVRAM)
Daylight Savings - (summer = yes, winter=no, saved in NVRAM) ________
Telescope - 4504/114EQ if firmware is patched, else use DS-127 (saved in NVRAM) _______________________
Alt/Dec ratio: -3.28533 (ratio for the mount's 1:144 worms, saved in NVRAM, reset by telescope model change)
Az/RA ratio: 3.28533 (ratio for the mount's 1:144 worms, saved in NVRAM, reset by telescope model change)
Train Drive (gear backlash compensation, saved in NVRAM)
*Train Drive - Alt/Dec, Az/RA number (backlash values, <650 is good, saved in NVRAM)_______|_______
Alt/Dec Percent, Az/RA Percent, 75% often works good for GP mounts, saved in NVRAM) ______|______
SEMI-IMPORTANT AUTOSTAR SETTINGS:
Min. AOS (satellite altitude begin tracking value, saved in NVRAM) ____________________
Max. Elevation (avoid mount crashes, saved in NVRAM) _____________________________
Mount (Fork mount, Alt-Az or Polar configuration, saved in NVRAM) ____________________
Cord Wrap (important for some models, not for others, saved in NVRAM)________________
Contrast Adj., Brightness Adj. (saved in NVRAM)
UNIMPORTANT AUTOSTAR SETTINGS:
Focal length (used for eyepiece calculations and spiral search feature, saved in NVRAM)
Sun warning on/off (for experienced users, saved in NVRAM)
Help screen on/off (for experienced users, saved in NVRAM)
Battery Alarm on/off (works poorly anyway, NOT saved in NVRAM)
High Precision on/off (less useful than you would think, not saved in NVRAM)
Quiet Slew (does not work on most telescope models, saved in NVRAM)
Owner Info. (informational only, saved in NVRAM)
Beep (you guessed it, saved in NVRAM)
LXD55 Adjust (I am not sure what this is yet, saved in NVRAM)
*Patched firmware feature only
14
FIRST TRIAL RUN
Now that you have learned a little bit about the Autostar and hopefully have it properly configured for your mount, we
can now move onto your first trial run!
In the interests of simplicity and rapid success, we are going to start with the mount in the Alt-Az position rather than
the standard RA/Dec Polar position.
The reason I want to start with Alt-Az is because it is actually a superior
configuration for most things and is much easier to get aligned under the stars.
The only exception is astrophotography at medium to high magnifications and/or
medium to long exposure times. What happens is the image in the eyepiece will
slowly rotate. This is because the axes of your telescope are not square with the
Earth's rotational axis.
Some of the advantages of the Alt-Az configuration are:
Faster, easier and more successful alignments.
Less chance for mount crashes.
An eyepiece diagonal can always be pointing up.
No requirement to flip the OTA when crossing the zenith.
More convenient eyepiece locations more often.
No need to patch the standard Autostar firmware.
IT IS MUCH EASIER TO TROUBLESHOOT, FIGURE OUT AND SOLVE
PROBLEMS WHEN YOU ARE IN ALT/AZ! Polar can come later!
GETTING INTO THE ALT-AZ POSITION
On SP mounts it is simple. You will loosen the main latitude (a.k.a. declination)
hex screw, which will allow the mount assembly to be swung back until the polar
scope is pointing straight up. You may have to remove the polar scope
cover and/or the latitude fine adjustment hand screw.
On most clone mounts it is a bit more complicated. You have to remove
both of the latitude hand screws, as well as the front plate that the front
screw threads through.
Anchoring the mount in the Alt-Az position is a bit more tricky. Tightening
the latitude axis bolt might work okay. You may have to pry off the covers
to get to the bolt and nut. The SP should be easier to deal with than many
of the clones. If you are unable or unwilling to fiddle with the latitude axis
nut, you can either work with the hand screw holes and shorter replacement
short metric screws or you might simply put the mount over as far as it will
go and then adjust the legs to compensate and make the RA/Az axis
perpendicular to the ground.
BASIC ALIGNMENT AND LEVELING
Basic alignment and leveling in the Alt/Az configuration will consist of getting the Az/RA axis perpendicular to the
ground and then getting the Alt/Dec axis perpendicular to true North/South. While standing behind the scope, the OTA
will be to your right and the counterweight will be to your left. Make sure to move the counterweight so the OTA is
balanced. The OTA will be pointing at true North, as defined by Polaris (Northern hemisphere). Magnetic compasses
don't usually cut it for determining true North, since the difference between true North and magnetic North might be as
much as 30 degrees. If Polaris is not visible from your viewing location, you can use a compass if you find out what
your local magnetic deviation is and compensate accordingly. Also don't hold the compass close to any ferrous metal
objects while determining North! There are some URL's on the Resources page that should help you determine your
local magnetic deviation. Those people in the Southern hemisphere will have to approximate the Southern celestial
pole ("True South") as best as they can from a Southern star chart. Fortunately, Alt-Az configuration is rather forgiving
about True North/South accuracy for GOTO mounts.
15
EASY ALIGNMENT (Align: Easy)
Aligning the telescope while in Alt-Az is very simple. The first thing
you have to do is invest in a small torpedo-style level. The next thing
you are going to do is level the tripod. If you are having trouble
keeping your Alt-Az configuration square because you are having
difficulty tightening the latitude bolt, you are going to want to level your
Az/RA axis so it is perpendicular to gravity instead. I made a bubble
level replacement for the polar scope dust cap, as shown below.
Adjust the legs to level the polar cap bubble level. If you do not plan
to use Alt-Az in the future, you can just approximate level for now and
not bother making a polar scope dust cap bubble level. After you have
become familiar with the mount's GOTO behavior in Alt-Az
configuration then you can go on to focus on the polar configuration
and not look back.
Here is what I do to get excellent Alt-Az alignments with Autostarpowered scopes:
1. Engage the axis locks but leave just enough slip so nothing will get
damaged if the motors accidentally drive the OTA into the mount.
2. Power-up the Autostar.
3. Enter the correct date, time & daylight savings time info.
4. Press ENTER to initiate the Easy Align procedure.
5. Use the keypad arrows to aim the scope precisely at the North Star, Polaris. (Just approximate North for now)
6. Use the keypad to lower the scope to level, as confirmed with the bubble level. Don't touch the left and right arrow
buttons after getting Polaris centered!
7. Once the scope is level and is still accurately pointing North, Press ENTER to have the Autostar slew to the first
alignment star.
8. Use the crosshair eyepiece (if you have one) to center the first alignment star as accurately as possible. (Just
pretend to do this for now)
9. Press ENTER so the Autostar can register the location and begin slewing to the second alignment star.
10. Use the crosshair eyepiece (if you have one) to center the second alignment star as accurately as possible. (Just
pretend to do this for now)
11. Press ENTER so the Autostar can register the location and begin tracking the sky.
12. Done!
SLEWING TO INVISIBLE OBJECTS
Now that your scope is theoretically aligned, go ahead and tell the Autostar to slew to some objects in the sky. If all
goes well, the scope will do what you expect it to! If not, make sure that you are giving it good instructions before you
assume that something is wrong with the mount setup.
After several evenings of indoor experimentation you will be ready for your first outdoor tests. Take your scope out
before dark and perform a "train drive" operation on both axes. This will tell the Autostar about the backlash you have
in the gears of both of your axes. Doing a good job here will pay off with better GOTO and tracking results later. After
dark and after your scope has cooled down and equalized with the outdoor temperature, go ahead and align your scope
on Polaris and the guide stars and then see if you can find things!
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OUTDOOR TESTING
Outdoor testing is going to require a few more considerations than
indoors. Batteries lose efficiency when they get cold. Tripod leveling is trickier
and more unstable on soft ground. Be careful dropping stuff. Make sure your
scope is allowed to cool down to outdoor ambient temperature.
Training your axis motor backlash values into your Autostar should be done
outside during the early evening, before dark. You will need a remote terrestrial
object to aim at for the Autostar Training function. If you do not do a careful
backlash train on both of your axes, your GOTO and tracking accuracy will
suffer.
POLAR ALIGNMENT AND AUTOSTAR SETUP
The polar alignment method you use will depend on if you are using a patched
Autostar firmware image or not. Since all of the DS-Series telescopes have Alt/
Az mounts, a polar configuration option is not normally available when those
models are selected. If you tell your Autostar you have an ETX-Series
telescope you can select a polar mount option, but it is tricky because the ETX
scopes are all fork mounts. This means that the Autostar will think your scope
is a fork mount too. The polar "home position" will consist of the same "scope
tube on the right and counterweight on the left with the counterweight shaft
parallel to the ground" orientation that is used by the Alt-Az home position. This
works, but you will have to carefully watch for mount crashes. The Autostar
does not correctly understand "flipping the axis" when crossing the zenith,
either.
If you upload a patched firmware image into the Autostar, you will be able to
select the "4504/114EQ" telescope model. That scope is a GEM and its home
position is more manageable. You will set the mount's correct latitude
adjustment, swing the RA axis until the OTA is directly over the mount and the
counterweight is at it's lowest point. You will then swing the Dec axis until the
OTA points at true North, or at least at Polaris, which will usually be good
enough. That will be the starting point for powering-up the Autostar.
I would encourage you to stay with Alt-Az until you have worked out all of your
installation and operational bugs as well as become familiar with the Autostar.
Polar adds a whole new level of operational complexity and if you are having
some kind of installation or operational problems, they will become just that
much harder to isolate and solve.
PC INTERFACING
Interfacing the Autostar is important. This is almost the only way to get
upgraded firmware and non-Meade patches into the Autostar.
Using a PC with planetarium
software to control the Autostar is
possible but I have found that to not
be as interesting or reliable as the
Autostar used by itself.
Schematic diagram of 505 cable
123456
1234
RJ-12 plug,
bottom
RJ-11
connector
Actual wire colors are not
important. Cable is
"rolled" just like a
standard telephone cord.
RJ-11 plug,
bottom
654321
DB-9F
connector 123456789
17
RESOURCES
Web sites
Yahoo discussion groups
http://www.meade.com
http://www.meade.com/catalog/autostar/497_autostar.html
http://www.meade.com/manuals/autostar/index.html
http://www.meade.com/support/auto.html
http://www.meade.com/support/etxautofaq.html
http://groups.yahoo.com/group/RoboScope
http://groups.yahoo.com/group/ScopeMount
http://groups.yahoo.com/group/meadeds
http://groups.yahoo.com/group/Meade-Uncensored
http://groups.yahoo.com/group/ETXASTRO
http://groups.yahoo.com/group/MeadeETXOwners
http://groups.yahoo.com/group/telescopes
http://groups.yahoo.com/group/Meade4504telescopes
http://www.data-plumber.com
http://www.data-plumber.com/autostarupgrade.htm
http://www.data-plumber.com/dsmotors.htm
Machine tools
http://www.weasner.com/etx/menu.html
http://www.weasner.com/etx/autostar_info.html
http://www.weasner.com/etx/autostar/as_patches.html
http://www.weasner.com/etx/autostar/patches/v26ec.html
http://www.weasner.com/etx/autostar/as_schematic.html
http://bedair.org/ScopeStuff.html
http://members.aon.at/wallnerstelescopes
http://feagle.com/astro/CG5/index.html
http://www.sherline.com
http://www.taigtools.com
http://www.smithy.com
http://www.ismg.com
Other Sources
Meade technical support (be careful what you admit to!)
Your local high school or college machine shop!
http://www.handsonoptics.com (friendly Meade dealer)
http://www.telescope.com (battery packs, general accessories)
http://www.televue.com (world's best eyepieces)
http://www.universityoptics.com (great eyepieces at great prices)
http://www.geolab.nrcan.gc.ca/geomag/e_magdec.html (determining true North from magnetic North)
http://www.geolab.nrcan.gc.ca/geomag/e_cgrf.html#MIRP (determining true North from magnetic North)
http://www.sdp-si.com/D780/HTML2/D780SA009.html (6mm shaft extender, part # S52FCYM060060)
http://www.oselectronics.com/PDF%20Pages/pg098.pdf (1/4" shaft extender, part # S150)
A few words on Autostar firmware patching
What are these patches all about? They are changes made to the computer program code stored inside of the
Autostar. The Autostar is a simple computer that has been dedicated to the single task of driving a telescope around
the sky. The Autostar contains a popular CPU called the 68HC11. The 68HC11 is well known by many electronics
enthusiasts and especially by people who are very active in robotics. Dick Seymour has done a lot of work to decode
the Autostar program and found interesting changes that could be made. Things like enabling features that would
normally not be available with some telescope models. Or things like allowing the direct editing of the backlash values.
The big reason that these patches are of interest to people attempting the retrofitting of Meade DS-Series telescope
motors to Vixen GP-style mounts is that without Dick's patches, you would not be able to select the polar mount
configuration when the Autostar has detected DS motors and is thus assuming they are connected to an Alt-Az-only
mounted telescope. There is a great deal of discussion on Mike Weasner's web site about Autostar firmware patches
and I would encourage you to go there to learn more about the Autostar firmware code and Dick's patches to it.
The process of modifying the Autostar firmware with Dick's patches might change in the future but for now, you will
download the official Meade firmware image from Meade's website to your \Program Files\Meade\ASU\Ephemerides\
folder and make sure to get the appropriate patch kit from Mike Weasner's web site for that firmware image and put it
into the "Ephemerides" folder too. Of course I am assuming that you have downloaded and installed Meade's ASU
program too! Follow the instructions in Dick's "readmeXXXX.txt" file. After successful patching, run ASU with the
Autostar connected to the PC via a Meade #505 (or home made) cable. Tell ASU that you want to "Upgrade Autostar
Software" from a "local:" file. Dick's patched images currently have a "4c" at the end of them. Select the image you
want and tell ASU "OK" to start the download. The download process is slow but might finish between 80% and 100%
download, which is normal. Don't interrupt the download process! Make sure the Autostar has reliable power
during firmware downloads! For more information, go to Mike Weasner's web site or to the Yahoo discussion groups
for more help. I would prefer to use the RoboScope group for retrofit discussions.
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GLOSSARY OF RELEVANT TERMS
ALT/AZ - Altitude/Azimuth. A telescope mount configuration in which the azimuth axis swings horizontally left-right
and the altitude axis swings vertically up/down. This has traditionally been the most common telescope mount
configuration for terrestrial viewing. Until GOTO technology came available, Alt/Az was unable to track the sky. Now
computers can correctly track the sky with an Alt/Az mount. The only thing that the computer can't compensate for is
rotation of the eyepiece field of view. This is a problem for long-exposure astrophotography unless a field de-rotator is
placed between the camera and the telescope. De-rotators are expensive and do not always work effectively enough
to give satisfactory astrophotographic results.
AXIS CLUTCH - If you are lucky, your GEM axis locks can act as clutches. In other words, you are able to select the
amount of grip between the axis and the worm wheels. This is very desirable for GOTO GEM mounts in preventing
mount crashes from damaging things.
AXIS LOCK - The little levers found on the side of the two axes of the GEM mount. They usually swing through a 1/4
to 1/2 turn to lock and unlock the worm wheel from the axis.
CRASH - The process where the OTA or some part of the Declination/Altitude axis components hit the rest of the
mount while under motor control. This is a bad thing. The most common result is an Autostar "motor failure" message,
requiring a power-cycle of the Autostar and going through another initial alignment. If you are real unlucky, you will
strip one of the tiny plastic gears inside one of the motor assemblies. If that happens, you will be calling Meade or
buying a spare set of motors or having a new plastic gear machined. Bummer! Make sure that if you can, do not set
the axis locks so tight that a gear has to give out before the axis lock begins to slip under the stress of a crash. Putting
too big of a battery pack on the GOTO system can actually make this problem worse instead of better.
GEM - German Equatorial Mount. A telescope mount configuration in which the Right Ascension axis points directly at
the celestial North Pole (a.k.a. True North) and rotates at a rate to (hopefully) precisely compensate for the rotation of
the earth and the Declination axis swings perpendicular to the RA axis, allowing the telescope to point anywhere in the
sky. This has traditionally been the most common telescope mount configuration for celestial viewing. GEM mounts
only need one constant-speed motor on the RA axis to compensate for the rotation of the earth.
GOTO - Go to Celestial object. Computer controlled motors drive the scope to accurately point at celestial objects.
The computers are usually dedicated to this task and contain databases of the most popular celestial objects.
Computers that boast of having 60,000 objects in their database are no more useful than ones boasting of 10,000
objects, since only about the top 2,000 objects are visible in most amateur telescopes. GOTO computers have to know
the sky as well as how to adjust for the viewer's location (latitude & longitude), the current date and local time. With
that information the computer is able to superimpose the known celestial sphere stored in its database with the current
position and perspective of the telescope. When that is successfully done, the computer can accurately point the OTA
at whatever celestial object the owner wishes with a fairly-high degree of accuracy.
OTA - Optical Tube Assembly - The optical scope tube.
PEC - Periodic Error Correction. The ability of some GOTO computers to "learn" about the periodic error in the worm
drives.
PERIODIC ERROR - Very small errors/imperfections that inevitably exist in the worm drives. As the worm drive goes
through a complete rotation, the error pattern repeats. The best-quality mounts have very small PE. If the PE is bad
enough, autoguiding feedback mechanisms or PEC features are unable to compensate fast enough and the mount will
be unsuitable for astrophotography.
RANDOM ERROR - Very small errors/imperfections that inevitably exist in the worm wheels. As the worm wheel goes
through a complete rotation, these are the small and unpredictable errors caused by irregularities in the teeth or by
contaminating particles between the worm wheel and gear. The best-quality mounts have very small RE. If the RE is
bad enough, autoguiding feedback mechanisms are unable to compensate fast enough and the mount will be
unsuitable for astrophotography. Random error can frequently be improved by "running in" the drive. Unclamp and
slew through many rotations of the final driven gear.
SLEWING - The process of moving the OTA to a new position. Either under manual or motor power.
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TROUBLESHOOTING
Rubber Banding
Rubber banding is when you tell your scope to GOTO an object and then you attempt to center the object with the
keypad, only to discover that the Autostar then slews right back to where it put it in the first place! This is most
commonly caused by poor motor training. Retrain your motors and try again.
Random Slewing
This is when your scope seems to be posessed, doing it's own thing at random times. This is most often caused by
poor electrical connections or poor power. double-check your connectors for corrosion or poor seating. You might also
consider re-crimping the RJ-11 and RJ-12 connectors. Make sure you are using good, clean 12VDC power with a solid
connection to your control panel. I would say 1 amp or so minimum capacity. Some 120VAC to 12VDC adapters have
poor regulation and can cause Autostar problems. You might also have electrically-noisy DS motors that will need the
resistor-capacitor modification referenced here: http://www.data-plumber.com/dsmotors.htm.
Creep After Beep
This is another pesky problem and is usually another electrical connection, power or motor noise problem. Same
solutions as for random slewing.
Alignment Failures
This happens when you are driving the scope too far to the selected alignment star for the Autostar's liking. Probable
causes include poor alignment starting position setup, incorrect location information, incorrect date or time or daylight
savings mode setting, swapped motor plugs in the control panel, incorrect ratio settings or signs and probably some
other stuff I haven't thought of yet.
Wildly Bad Pointing
This might happen if you have a poor alignment starting position setup, incorrect location information, incorrect date or
time or daylight savings mode setting, swapped motor plugs in the control panel, incorrect ratio settings or signs and
probably some other stuff I haven't thought of yet.
If you mount your motors on the opposite ends of the worm shafts than what is described in this document or if you use
gears or pullies and timing belts then you will have to reverse the polarity of the worm ratio for that axis. And of course
two reversals together (opposite end combined with gears, for example) will cancel each other out. Having the Alt/Dec
motor on the right hand side of the OTA would require a worm ratio sign reversal too. It is possible to open the motors
and reverse the leads to the motor rather than enter a negative sign for a particular axis', but I don't recommend that
approach.
Poor GOTO accuracy
If everything is close but not on the money, double-check your motor training and training values (<650 is acceptable),
alignment starting position setup, careful alignment procedure (get a cheap crosshair eyepiece from University Optics
or Hands On Optics), and for loose mechanical problems somewhere.
Mechanical backlash settings of GP-style mounts is outside of the scope of this document for now. If anyone is aware
of a good how-to FAQ on that subject, please let me know so I can add its URL to the resources page. If we don't find
one I will probably be motivated to eventually create one.
Motor Fault Errors
This can happen when the motors are stalled by a mount crash or by power or cabling problems. It can also happen if
you swap around your motors or replace a motor. "Calibrate Motor" should always be performed when swapping
around motors. In fact doing a full reset and starting fresh is often a good thing to try whenever everything else fails.
20