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Polar Alingment, how Precise Can the Meade ETX Autostar Observation System
Be?
Polar Alingment is require for Astrophotography. The Meade Autostar
is designed to compensate for a lot of user errors. If your time, location,
and alignment (Polar alignment, star alignment) are not exact, the tracking
will not be correct and the GOTO will be inaccurate. The field of view
of a 26 mm eyepiece on the Meade ETX-90 is about one degree. The straight
viewfinder 8 x 21 mm has a field of view of 6.8° straight or 6.4°
for the right-angle viewfinder. It is possible to have the star appear
in the eyepiece 90% of time on GOTOs with a precisely completed setup.
For a less precise setup, the star may not appear in the viewfinder. It
might appear just outside the viewfinder's view.
What Affects
the Meade ETX Autostar Observation System?
The perfect
result of a process is the precise completion of all of the
steps that lead to the result. The more precise each step
is, the more precise the end result will be. Every little
error introduced at each step of the process results in larger
error at the end. A precision result can only be achieved
if all of the steps are completed with precision. For example,
entering the exact Altitude and Longitude of your house instead
of choosing the closest city in the Autostar would introduce
less error. The closest city could be many miles away. Entering
the exact time read from an atomic clock instead of the time
from the microwave oven would introduce less error. The time
on the microwave oven might be inaccurate. A tripod that is
not perfectly level would cause the Azimuth movement (horizontal
turning) to not be fully horizontal. This inaccuracy could
also cause the Altitude movement (vertical) to not be plumb.
Your polar alignment and star alignment therefore would not
be precise. The Meade Autostar also compensates for a degree
of free-play on the motor and drive gear system. There are
settings for the degree of telescope drive system free-play.
These settings must be precise as well in order for polar
alignment and star alignment to be accurate.
What Gives
You Consistency?
There will
be no consistency without precision steps. All of the stars
are many light-years away. Therefore, a small error here, a
little inaccuracy there, and things start to add up to create
significant problems. If setup properly, the Meade ETX Autostar
telescope is amazingly precise even at such a low cost.
There
are no overall instructions for the beginner. There is a manual
for the telescope on how to use the telescope. There is also
the manual on how to setup the Autostar. There may be a manual
for the tripod. These manuals are not integrated. They deal
with each piece of equipment individually without any integration
between them. It is important that each piece work with the
other pieces.
The Goal
My experience
is that, with a proper and precise setup and alignment (polar
alignment and star alignment), you can expect better that 80%
of your GOTO targets will appear (not necessarily centered)
in the 26mm eyepiece of the Meade ETX-90EC. All target stars
will appear in the viewfinder. A somewhat less precision alignment,
will have all the target stars appear in the viewfinder but
not necessarily in the eyepiece. If you follow the instructions
here, you will get good GOTO accuracy and night-after-night
consistency.
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