Might even be able to do this with a camera
targeted on Polaris, to eliminate the complications of tracking,
The whole idea of generating a PE curve is to measure tracking, so if you aim the camera at the pole, you won't get any data. But not to worry, PEMPro automatically sends your mount to the celestial equator, where the tracking rate of a star is almost exactly sidereal. Any departure measured by PEMPro is then the PE.
Rolando
-----Original Message-----
From: 'Joseph Zeglinski' J.Zeglinski@... [ap-gto]
To: ap-gto
Sent: Sat, Feb 3, 2018 1:16 pm
Subject: Re: [ap-gto] Needing re-do the PE after updating 1200 cp3 L chip to V chip.
Hi,
I suspect you may dread being out there in the cold
winter night, capturing raw data for the curve. Luckily, sampling 6 to 8 raw
data cycles will take over an hour anyway, and once started, doesn’t
require your presence at the mount – good time for an indoor coffee break.
Later, even the PEC analysis and final curve fitting can be leisurely done
indoors as well, then just upload the result into the CPx mount
controller.
Programs that calculate the PEC wave pattern on the
gear train teeth variations, need “some kind” of reference.
A bouncing star is ideal because it is simple. I suppose it
might be theoretically possible, but impractical – to do the PEC curve
generation in daylight, or even in the house, using a commonly available
“simulated star” or compare successive frames of a room scene (or a precisely
printed target), for their shifting. But it would be less precise and require
much more computer resource. Might even be able to do this with a camera
targeted on Polaris, to eliminate the complications of tracking, PA, cross
winds, and drift from the process – but not a present capability in any PEC
generating software I know of.
So, PEC generation can only be done with a camera
centered on a reference star.
Luckily, PemPro doesn’t require a
perfect polar alignment to do this part of the job – it compensates internally
for many things, including an arbitrarily CCD rotation, although a reasonably
close CCD rotational alignment with the axes, and a good initial mount polar
alignment would probably help it producing a slightly more accurate curve. But
such detail isn’t really necessary, since normal “seeing conditions” could
affect guiding more, in spite of a good PEC curve. But, everything helps.
PEC is only needed for imaging and not
for visual use with the mount, since visual use won’t see minor position
variations. Since you will be doing it soon anyway, just be patient and leave
the PEC curve generation for that first night out there under the stars with
your CCD. PemPro makes it easy and indeed fun to do.
