Thanks for the detailed explanation.
On 6/09/20 2:47 pm, Jerry Hubbell -
Explore Scientific VP Engineering wrote:
On Sat, Sep 5, 2020 at 07:51 PM, Steve Lang wrote:
I've had no problems like this in the past at all that
I can remember.
Wes emailed about this, here is how I responded:
Any idea what might have gone wrong? Could it be a bug/condition
triggered (because I'm in southern hemisphere)?
"The problem is not the meridian flip done at zenith. All the
mount cares about is what side of the meridian it is on, it
doesn’t give a hoot about where DEC is. The problem here is
related to the plate solve when near the meridian.
I have talked about this at least 2 times in the forum when
people run into it. What happens is that if you are near the
meridian and the mount is slewed to an object which the mount
thinks is currently on the east of the meridian (which it is).
You take an image of the sky, and the pointing is off enough
where the current position is west of the meridian. The pointing
was off enough from where the mount thought it was. In this
case, as soon as you do a plate solve and a SYNC, you now tell
the mount, “hey, you are actually west of the meridian!” and
calculates the motor counts according to that position. The
problem is created at that point.
The calculation of the motor counts depends on which side of the
meridian you are on of course for both RA and DEC. So now the
mount is 180-deg out of phase (the motor counts) so when you go
to slew to the object again, it will point the mount to the
ground. My advise on the forum is to never do an initial plate
solve on an object within 10 arc-minutes of the Meridian.
You must make sure that any object you are pointed at in the sky
and you have photographed is actually on the side of the
Meridian that the telescope is pointed at before doing a SYNC."
Vice President of
Explore Scientific, LLC.
jrh at explorescientific.com
1010 S. 48th Street
Springdale, AR 72762
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