The following article is a re-posting of a piece that appeared in Issue
6 of Photon E-Zine.
Roboscoping!
By Tom Nicolaides
I’ve been interested in Astronomy since I was a little kid.
At the age of 8 my dad bought me a Gilbert 2.5 inch reflecting telescope.
I couldn’t see a whole lot through it, but I could see craters on the
moon and the moons of Jupiter.
I was
hooked.
In high school I got a Criterion RV-6 six inch
reflector.
I could certainly see a
lot more than with the old Gilbert (a toy).
In college I got a job with the physics department and operated their
observatory for the general public.
It
was a pretty good scope – a 6 inch F15 refractor – and this was long before
the commonly available refractors of today.
Even from the light-polluted city of New Orleans I could show visitors Venus, Jupiter,
Saturn, Mars, the Moon and some deep space objects such as M31, M57 and open
clusters.
Upon graduation I got married, raised a family and while
I didn’t lose interest in astronomy, I was not active.
Occasionally I’d pick up a Sky and Telescope
magazine and look at the new developments and advertisements.
Well, my family is grown now and a couple of years ago I
purchased an Orion Astroview 120mm refractor on a German equatorial mount
with manual slow motion controls.
I
wouldn’t say I was disappointed with the scope – it gave fine views – particularly
of the moon and planets open star clusters and brighter nebulae.
The problem was I was spending more time hunting
deep space objects than actually looking at them.
So I’d get my new Sky & Telescope magazine,
read about the DSOs that were visible and not take out the scope because of
all the effort in finding these astronomical wonders.
Not long after I was scanning eBay listings and I came across
a motorized Meade mount.
It didn’t
have “Go-To” capability, but the seller assured me that with the addition
of Meade’s Autostar hand paddle it could be made to be so.
So I bid on the mount, won the auction and it
arrived.
First thing I found was the
mount was vastly undersized for the Orion OTA.
However, I did mount it in the cradle and took it out.
It was fun pressing the buttons and having the
OTA move.
But it was no easier to find
anything and there was no sidereal tracking to keep the object in view once
I did find it.
I later learned that
it was a mount from Meade’s lower end scopes and wasn’t well-thought of by
serious amateur astronomers.
Still,
I went ahead and found a used Meade Autostar 495, ordered it and hooked it
up.
With excitement I took the scope out first clear night.
I followed the instructions for alignment and
amazingly it worked – sort of.
That
is, I could tell it to go to objects that were fairly bright and it would
bring me reasonably close – within a few degrees.
But I could tell that on dim telescopic objects it wouldn’t be accurate
enough.
Also, that inexpensive Meade
mount was seriously unstable with the Orion OTA.
Focusing was difficult at high power – too shaky.
I needed to improve it.
I started to do some web searching and I found a pile of
web sites devoted to converting telescopes to go-to operation using Meade
parts.
Some of the methods involved
using the motors from the mount I got off of eBay, the Meade Autostar paddle
and a good German equatorial mount.
For
this information I need to thank Mike Weasner, Chris Erickson, Steve Bedair,
Peter Vasey and many others.
I discovered
several ways of attaching those Meade motors to my mount.
I selected a method that involved machining
a coupler to the worm adjustment shaft on my Right Ascension and Declination
shafts.
Enlisting the help of a machinist
friend of mine we went to work one Sunday morning and by late that evening
we had a pair of couplers that fit right onto the mount.
Then I discovered that in certain configurations
the motors clashed with each other.
Clearly modifications were in order.
So I kept the coupler for the RA shaft and made
a new one out of right angle aluminum and duct tape and fastened it onto the
declination axis.
Right Ascension Motor
Declination Motor
– showing high-tech duct tape
View showing RA and
Declination Motor mounts
Well, Success!
The
motors turned the axes easily.
That’s
about the time I discovered the Autostar 495 hand paddle doesn’t know about
German Equatorial Mounts – Alt-Az mounts only!
However, I learned that Dick Seymour has patched
Autostar firmware to include GEM type mounts, but I would need Meade’s Autostar
firmware loader and a cable.
On Mike
Weasner’s site I found the schematic for the necessary cable.
From Meade I got the Autostar firmware loader.
From Radio Shack I got the parts necessary to make an RS-232 cable
that connects to the Autostar.
From Dick Seymour (via Weasner’s site) I got
the patches and new firmware.
I ran the firmware loader and had no trouble getting the
new firmware into the Autostar.
The
interesting thing is that for all practical purposes I now have Meade’s more
expensive 497 hand paddle - All by doing a firmware update.
Upon loading I found various types of GEM type
telescopes listed.
I selected one and
tried doing an alignment that night.
The
setup didn’t even come close to finding the alignment stars – half the time
the scope ended up pointed at the ground.
So some more research was in order.
That’s when I found Peter Vasey’s site.
He converted a mount almost identical to mine.
I learned that Autostar assumes a default gear ratio on the worm drive.
Autostar was expecting 100 teeth on the worm gear.
According to Peter I had 65 on declination and
130 on RA.
Autostar provides a place
in their menu to input new ratios.
The
Meade manual warns the user never to change these numbers.
So change them I did, to the numbers Peter had
listed on his site.
The scope still
pointed towards the ground.
Hmmmmm,
Something else, then?
On
Bedair’s site I found a more comprehensive explanation of gear ratios.
It turns out that the sign is significant.
That is, plus or minus.
He states
that if the telescope turns backwards, the sign is probably wrong.
Could that be it?
Two numbers
mean four possibilities on signing.
++,
+-,
-+, or
--.
I tried ++ already, so I switched to + declination and – RA.
No better.
Okay, then we’ll
make both negative.
Still didn’t work.
That left negative for Declination and Positive
for RA.
I tried alignment one last
time.
The Autostar told me it was selecting
Vega for alignment.
I felt immensely
satisfied when the scope smoothly slewed over to the direction of Vega and
placed it into the field of view of my finder.
With growing excitement I centered Vega, hit
OK and the scope told me it was using Deneb as the
next alignment star.
The scope moved,
I looked into the finder and there it was, almost dead center.
I hit OK, the Autostar said CALCULATING and
then ALIGNMENT SUCCESSFUL.
Wow!
The Autostar then switched over to OBJECT mode in which I
could select things to look at.
Since
I was already in the area I selected M57, the Ring Nebula.
I knew how to find it myself and I always liked
looking at it.
I told Autostar to take
me there and without even looking in the finder it placed it in the FOV of
an EP that gave me 66x.
It was an amazing feeling.
It felt like I’d discovered M57 myself!.
I tried a lot of other objects that evening.
In that one night I saw more DSOs than I saw
during all the time I was active in astronomy combined.
It has greatly increased the pleasure of observing.
That’s not to say there were no problems.
In trying to improve performance I went through
a procedure to “train” the drive – Not only did it make pointing worse, through
a bug in Meade’s firmware it made it almost impossible to center an object.
But with the online help available I was able to conquer the “rubber
banding” effect, as it’s called.
I’ve since bought other Meade motors and just completed converting
another mount to Go-To operation.
The
enjoyment of being able to observe using Go-To, coupled with the deep satisfaction
of using equipment that I built and modified myself has vastly increased my
enjoyment of our hobby.
Now I go out
almost every clear night.
Me and my Roboscope
Helpful Links:
Yahoo Roboscope group:
http://groups.yahoo.com/group/RoboScope/
Chris Erickson’s Conversion Site:
http://www.data-plumber.com/autostarupgrade.htm
Steve Bedair’s site:
http://bedair.org/ScopeStuff.html
Peter Vasey’s conversion site for the EQ3-2
http://mysite.wanadoo-members.co.uk/equipnbits/EQ3.htm
Weasner’s Autostar Information
http://www.weasner.com/etx/autostar_info.html
