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I think I finally realized - it finally sunk in - WHY you are always so
"unconcerned" about accurate time - as far as tracking and GOTO is concerned.
Let's see if I got this right. For example, let's say I "purposely" set
the local time 3 hours in error !!! Assuming that I know my way around the
sky, I could point the scope manually to the correct alignment star, and
synchronize the mount. After that, it will track perfectly, no matter what
time it thinks it really is. Same thing about GOTO's - it will just do a
relative jump, and hit the target precisely, on the first attempt (after
As you allude, the only thing that can go wrong is that the controller
will think that the target has set below the horizon (prematurely), - or
perhaps it actually has set 3 hours before, but the controller thinks it is
still up - owing to my 3 hour intentional time error, and tries to hit the
ground in the attempt.
If I have this right, then I finally see that time is not that relevant -
though precise time is convenient so that GOTO's hit the mark on start up,
without my knowing the sky, or in the city, not being able to see the
alignment stars, without the GTOCP3 showing me exactly where they are.
So, correct time really is not essential, but it sure lessens our
Thanks for the enlightenment,
----- Original Message -----
Sent: Monday, July 02, 2007 9:49 PM
Subject: Re: [ap-gto] Re: computer startup sequence question
In a message dated 7/2/2007 6:08:41 PM Central Daylight Time,
I see your point. What I am trying to do though is make sure theFor your application there is no need - no need at all - to get perfect
mount gets it's start up info from the computer because I want to
make sure the mount receives the accurate time from the computer.
And I want to sync from the SKY to make sure precessed coordinates go
to the mount since the keypad is only going to send J2000 coordinates.
accurate time because you do not have a fixed permanent setup. Please try to
understand what time is for - it is strictly to calculate the horizon and
meridian. Object positions in the sky are not tied to time the way you
They are tied to each other, and initially they are tied to the first object
that you center in your telescope field. Time has no function in that
You are not starting off with a fixed mount where you might want to have an
accurate time for other unrelated reasons. Being off 1min, even 5 minutes
make no difference in your case (the keypad would not be off that much even
year's time). You are making things very complicated for yourself, and there
is no need to do that.
You can certainly sync from The Sky to an object to get your J2000
coordinates for that object, but frankly, it will make zero difference in
subsequent gotos if you start out from the keypad on that same object.
Placing your keypad in EXT mode is NOT something I would recommend that you
do. First, you are quite confused about what is necessary in time and
etc. EXT should only be used when you know exactly why you need it, and it
NEVER needed for a non-observatory setup.
See what's free at
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