Hi Roger,
Thanks for the post.
Quote:
Originally Posted by rogerg
So none of you guy's with ServoCat have problems with it?
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The ServoCAT itself is a mature, stable and immensely popular product, particularly
for medium to large Dobs.
It is a sophisticated system, comprising a dual axis servo controller, dual servo motors
with their own encoders, support for wired and wireless handpads as well
as communications interfaces for a DTC/DSC and well as a laptop/PC. The motors
have their own internal gear boxes and in turn are typically interfaced to each
axis of the mount by way of knurled coupling with the ground board for the Az
axis and via a cable drive for the Alt axis, both of which can be disengaged by
a couple of levers to allow the scope to still be pushed manually if the user desires.
When one considers the spectrum of accessories available for telescopes, at
one end of the scale you have components such as an eyepiece, where the
device has either no or few moving parts and if the optics designer got his part
right and the end user remembers to remove the eyecaps, then the chance of
having a problem with it is next to zero. At the other end of the scale you
have devices that are significantly more complex, like a Peltier cooled CCD
imaging system interfaced to an autoguider and via cables to a PC and a power
supply, all in turn under the control of some complex software. At this end of the
complexity scale, the chances of encountering a problem increases.
As we are all aware, this is true of many other disciplines , not just astronomy.
However, the point is that devices such as the ServoCAT are in the upper
half of the accessories complexity scale. For example, there are configuration
parameters that the user typically tunes and programs into the controller which
are specific to their own mount. There are mechanical adjustments that the
user can make. So as is typical of any equipment that can be mechanically adjusted
or configured in software, the chances of one never having encountering a problem
are greater than say compared to that of plonking in the eyepiece, where one
simply needs to remember to remove the end caps.
Since the ServoCAT is such a sophisticated device, Gary Myers at StellarCAT
backs it up by providing some of the highest levels of support for any
product on the astronomical market today.
Apart from direct email, there is the ServoCAT forum on Yahoo at
http://tech.groups.yahoo.com/group/ServoCAT/ and the StellarCAT office will
take phone calls up until 8PM at night Arizona time.
Quote:
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Don't find the cabling a nuisance ...
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With regards the cabling, most users use one of the stalks available from
Markless Astronomics in North Carolina.
See
http://www.marklessastronomics.com/d...0products.html
The ServoCAT device is typically mounted on the rocker and all cables
to it tend to be dressed via cable clips on the inside of the rocker and those
that need to run to the wired or wireless handpad controller and to the
DSC/DTC run up the tube of the stalk. Typical installations have only one
wire pair that runs from the scope to the outside world, namely the 12V power
supply, and the majority of these use the powered ground board option which allows
the power cable to be plugged into the non-moving ground board so the
cable is not rotating with the scope. A common practice is for users to throw
a piece of carpet or mat over the 12V cable so they don't trip on it.
Some of the smaller scopes use small 12V sealed lead acid batteries which
they mount on the inside of the rocker so they have zero external cabling.
Quote:
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.. or have problems with accurate tracking?
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Quote:
I have a mate who's installed ServoCat on his 15" Obsession some months ago ...
... And he hasn't got it tracking well enough to do his webcam imaging of the planets yet - drifts lots.
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On an Alt/Az mount, both axes track simultaneously and with continually variable rates.
In the ServoCAT architecture, the job of calculating these tracking rates in real
time is performed by the DTC/DSC, usually an Argo Navis, rather than by
the ServoCAT.
When a ServoCAT equipped scope does not track well, the first questions that
needs to be asked are does the system point correctly and does the GUIDE
display on the Argo Navis show very nearly 0.0 for both axes whilst the
scope is tracking?
If the scope does not point correctly, it is not because of the ServoCAT.
Pointing is the responsibility of the telescope computer. There are many reasons
why a telescope may not point to where the telescope computer 'thinks' it is pointing.
Typically this can be a result of what we term a 'Category 1' error, which includes
encoder installation problems and user setup errors or what we term 'Category 2'
errors, which are telescope mount fabrication errors.
Pointing errors should be addressed first.
Since tracking is the differential of pointing, poor pointing performance can
result in poor tracking performance.
The Argo Navis and ServoCAT form a closed loop tracking system. If after performing
a GOTO, the Argo Navis first shows 0.0 in its GUIDE mode display but if over
time these guide angle values increase in magnitude, then this usually points to
a ServoCAT parameter configuration issue.
Quote:
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... and he has intermittent problems where it doesn't behave
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This could well be an additional clue that it is simply a ServoCAT parameter
configuration issue.
Quote:
From his experience is sort of struck me that there's a lot to be said for keeping it simple and not having ServoCat 
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Better advice would be to suggest to your friend that he contact either Gary Myers
at StellarCAT or myself at Wildcard Innovations for assistance.
Like Gary Myers at StellarCAT, we pride ourselves on the levels of support we
provide. During the day, I am delighted to assist customers in person on the
telephone and we typically assist customers at night as well, including on weekends
by email and by responding on online forums such as these. For example, we even
provide support on Christmas Day. However, if the customer does not contact us,
then it is difficult for us to provide the support they need.
Likewise I know that Dave Kriege at Obsession is only too happy to assist with
regards any telescope related issues.
With the population density in WA being lower than many other parts of the
world, finding a fellow observer with an identical piece of kit to with whom one
can exchange knowledge is more difficult than say in cities like Sydney,
Melbourne and Brisbane. Having a friend that can help can be a big advantage
and for example, here in Sydney, any one observer is probably never that far,
as the crow flies, from someone else that actually owns a ServoCAT and who can
pass on advice. However, for those who are "on their own" as it were, free
support is still readily available.
So if you could please pass this advice onto your friend, we would appreciate it.
Thanks again for the post.
Best Regards
Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place
Mount Kuring-Gai NSW 2080
Australia
Phone +61-2-9457-9049
Fax +61-2-9457-9593
sales@wildcard-innovations.com.au
http://www.wildcard-innovations.com.au
