Hi Bob,
I thought I better make some corrections here as unfortunately there are
some errors in your post which, in the worse case if left uncorrected, might
lead some enthusiasts down the wrong path and cost them valuable time and money.
Quote:
Originally Posted by bobson
Lets compare the prices for handhelds
....
Now, there are many ways you can use those hand helds. As you know there are many yahoo groups explaining how to connect optical encoders to Meade hand held computer with more options than ArgoNavis.
|
With the exception of Argo Navis, none of the cited hand-held devices are for
connection to optical encoders. The generic hand display units like the AutoStar
are designed to interface to a set of additional electronics which is found within
the telescope mounts themselves. This additional electronics include subsystems
such as the motor controllers and power supplies. In other words, without this
additional electronics which is embedded within the mount, the hand controller
on its own is of limited utility. Meade refer to this distribution of the electronics
in their US Patent 6392799, entitled "Fully automated telescope system with
distributed intelligence".
Though some enthusiasts will interface generic hand controllers like the AutoStar
to stepper motor controllers and stepper motors they have salvaged from elsewhere
to provide a GOTO system, the statement that "
there are many yahoo groups
explaining how to connect optical encoders to Meade hand held computer"
is incorrect.
So when attempting to compare prices, the hand controllers like the AutoStar
on their own don't represent the whole story. This even becomes more self evident
when one "looks beneath the hood". When you open up and look inside the
generic third party hand controllers, there is usually a minimal amount of electronics
For example, the original AutoStar hand controllers have a low performance 8-bit CPU.
By comparison, the Argo Navis employs a dual CPU architecture including a 32 bit
CPU with full external 32 bit data buses, high speed caches and ultra fast static
RAM. This processing power enables the Argo Navis to perform tasks that the
lower performance units can't do, such as real-time name completion when entering
object names, the ability to sweep the scope across the sky and have Argo Navis
identify the object in real-time and very importantly on many home-built mounts,
provide the ability to analyse and potentially compensate for many of the typical
systematic generic fabrication errors that exist within the mount/OTA that might
affect its pointing performance otherwise.
Units such as the AutoStar assume that, by design, the mount they are interfaced to
is assembled to a sufficient degree of precision such that if any of the three
primary axes are not orthogonal or if here is any eccentricity in the bearings or
if they have any discernible gravitational flexure in components such as the OTA,
that it will not affect the pointing performance to the point that it won't meet its
designed pointing goal.
Unfortunately, with phenomena such as Dec to optical axis non-perpendicularity
on mounts such as generic Chinese GEM's being commonplace, sometimes the
scope fails to meet its pointing goal.
Argo Navis has an in-built feature called the Telescope Pointing Analysis System
(TPAS) which can analyze and potentially compensate for many of the typical
systematic fabrication errors found within mounts/OTAs. None of the generic
hand controllers cited offer anything comparable to TPAS with regards its
power and sophistication and again this is where processing grunt comes
into play. For example, we ran some benchmark analysis of processing
performance and found that a TPAS analysis of a large number of sampled data
points which took Argo Navis 5 seconds to compute would take the type of 8-bit
CPU found in generic hand controllers over a day to compute. However, even then,
the generic hand controllers had insufficient memory address space to do the
task even if one were to attempt to port the code.
The best telescope pointing analysis package on the market is called TPOINT
and was originally developed at the AAT here in Australia for use on the 3.8m
AAO. TPOINT is employed on virtually all of the world's largest and most expensive
telescopes, such as the VLT, to analyze their pointing. When one feeds pointing
data to TPOINT and Argo Navis's TPAS and sets equivalent model terms, the results
are essentially identical, as one assumes they should be. TPOINT is sold
commercially by Software Bisque and retails for US$249. On Argo Navis,
TPAS comes as standard and a few years ago was provided as a free upgrade
to all Argo Navis customers.
TPAS can make all the difference between a telescope meetings its pointing goals
or not and this can be the case not just with home-built mounts but with
commercial mounts as well. For example, there is an interesting case study on
the Wildcard Innovations web site at -
http://www.wildcard-innovations.com.au/group_post_5573/
This TPAS analysis was performed on a Losmandy G-11 GEM. You might need to
run the free Adobe SVG viewer from here to view the graphics -
http://www.adobe.com/svg/viewer/install/main.html
Argo Navis also includes a wealth of features not found in many of the generic
hand controllers.
Quote:
|
Now, think about it, how complex is one laptop to make and how complex is to make one ArgoNavis. The only excuse is mass production of laptops against Wildcards.
|
Though laptops and Argo Navis both employ computing at their core, they
are two different types of products that are designed for different purposes.
For example, most commodity laptops are designed to provide up to about
a couple of hours usage on a large, heavy lithium battery before needing
to be recharged. By comparison, Argo Navis is designed to operate for up to
a couple of nights non-stop, whilst interfaced to a pair of optical encoders,
the whole time running on nothing more than a set of commodity alkaline AA cells.
Whereas Argo Navis is designed so that it can be held and operated with one hand,
perhaps whilst wearing a pair of mittens, a laptop can be an awkward and intimidating
prospect to juggle atop the ladder of an instrument like a 20" Dob. Whereas
Argo Navis is designed to operate in environmental extremes, including being
left outside covered in dew or operating in freezing temperatures or possibly
getting dust blown over it during the day whilst mounted on a telescope,
such conditions would typically bring about malfunctions or early failures
in unprotected laptops. Should one accidentally drop the Argo Navis on the ground and
occasionally people do, chances are you will pick it up, blow off the dust and
keep operating without missing a beat. Laptops rarely survive equivalent drop
tests.
Both commodity laptops/notebooks and Argo Navis employ mass
production manufacturing techniques, but one should keep in mind that the
commodity laptop market is a much, much larger market than the astronomy
market. Worldwide, there might be something like 500,000 astronomy enthusiasts.
By comparison, just in 2009 alone, something like 35 million notebook computers
would have been sold worldwide. These economies of scale then result in the
low price points consumers enjoy for notebooks these days. If the number of
astronomy enthusiasts worldwide numbered the hundreds of millions, then
equivalent economies of scale for mirrors, eyepieces, focusers, CCD cameras,
motor controllers, telescope computers, etc. might also be enjoyed. Unfortunately,
despite the joy of observing, the astronomy market is best described as a niche
market.
However, as stated, Argo Navis employs state-of-art manufacturing facilities
and processes and this enables it to be put into the hands of enthusiasts at
price that, for what it does, provides excellent value for money. Let me
give some specific examples of how manufacturing processes allow this to
happen. Some outside of the global electronics industry might be mistaken
to think that one can simply build some electronics, package it up and start
selling it locally and exporting it. However, there are some tough and very
costly regulatory requirements that one has to meet in various jurisdictions
around the world. For example, the European Union (EU) and Switzerland
currently forbid the import of electronics that contain hazardous materials
such as lead. Chances are that if you have ever hand soldered a kit
together in recent years, the solder you would have used and the components
that you would have used would have both contained lead. If one then
exported such as kit to a destination within the EU, it would be within
breach of EU law and criminal penalties exist. One concern with electronic
devices is that they can radiate electromagnetic energy potentially
causing interference to communications infrastructure such as radio, television,
mobile phones, etc, or possibly induce failures in other electronic devices,
such as aircraft controls, pacemakers, etc. In nearly all jurisdictions throughout the
world there are legal requirements on the levels of radio emissions, the susceptibility
of a device to radio emissions, the amount of interference in can conduct through
its power cable, its susceptibility to electronic discharge, etc. etc. Virtually
all jurisdictions mandate NATA accredited test facilities to have tested the
device for sale and to have issued a certificate that the device is compliant.
Many of these tests are extremely expensive and without employing advanced
design techniques from the start, most electronic devices will fail them and will
thus be illegal to buy, sell, use, import or export.
Argo Navis uses only components that meet or better the regulatory requirements
and for example are free of materials such as lead and other materials on the
EU banned list. Rather than use solders made from an alloy of tin-lead, our advanced
manufacturing process uses solders based on alloys of tin-silver-copper. As part of
this advanced process, our PCBs currently utilize state-of-the art laminates and finishes
of nickel and gold to ensure the highest levels of quality and reliability.
So the good news is that since we have invested considerable expense into
ensuring that Argo Navis is compliant and can be legally sold throughout the world
and because we employ the same mass manufacturing techniques as
commodity consumer electronic devices, it means we can deliver telescope
computers into the hands of enthusiasts who would otherwise not have the
financial resources, investment in equipment and testing and the skills required
to manufacture them on their own.
So hopefully the above helps clarify some technical points. One of the problems
with posts with technical errors regarding telescope pointing is that it often
results in email queries invariably coming to me stating something like
"After reading about it from a guy on the net, I went and purchased a used
AutoStar on Astromart and now want to interface it to a pair of your encoders
on a 12" Dob. What do I need to do?" This then results in my having to
patiently spend considerable time and energy explaining the bad news that
what they are attempting to do is not possible.
Take heart that your recent advice in this post -
http://www.iceinspace.com.au/forum/s...4&postcount=82
is a thread we commonly hear and many users of DIY kits initially use them
as an introduction to computerized telescope pointing before upgrading to an
Argo Navis. Hopefully an Argo Navis will feature in your observing accessories
one day.
Best Regards
Gary Kopff
Wildcard Innovations Pty. Ltd.
20 Kilmory Place, Mount Kuring-Gai
NSW. 2080. Australia
) so I got a good price. A DIY solution has additional "costs" - the DIYer's time and possible troubleshooting, possible lack of upgrade options etc.
). I generally understand the pros and cons of both approaches.
glue two encoders to the laptop, 
