Re: Meridian Flip - Flop & Flexure compensation factor

W Hilmo

Lesser mounts deal with this problem by using multiple alignment stars. For
example, my Celestron mount uses two stars on one side of the meridian to
build the sky model, and then it uses up to 4 stars on the other side of the
meridian to calculate orthogonality error, which it then uses to correct
goto slews. It works well enough that, when doing visual with my C14 and
CGE mount, it puts any target - anywhere in the sky - near the center of my
31 Nagler.

Honestly, though, I have not missed this on my AP mount. When setting up
the mount in a new location, I just use a bubble level with the clutches
released to get the mount into Park 1. Then, I power it up, polar align it,
use the hand controller to go to a bright star and sync.

Once that's done, each night I just turn on the mount, connect the ASCOM
driver and resume from last parked. My automation software slews to the
desired target, syncs and does a second slew. I've got a pretty small field
of view with an ST-10 at 2300mm focal length and I'm using an SCT with the
associated mirror flop. Still, it's never missed the first sync (it takes
about 30 seconds; 20 seconds of exposure and about 10 seconds to solve) and
my target typically ends up within several arc seconds of the center of the
field. It's not uncommon for me to start the software before evening
twilight, leave it unattended, and get my sub exposures the next day before
powering down until the next evening.

I will say that it makes a difference what software plate solve routine that
I use. TheSkyX Pro seems to handle plate solving when slightly off target
better than Pinpoint does. I've got the software configured to use TSX
which gets me the above reliability. If I use Pinpoint, it sometimes takes
several minutes unless I am very close, and I've seen an occasional
incorrect solution.

Like everyone else, though, I am eagerly awaiting APCC Pro.



From: ap-gto@... [mailto:ap-gto@...] On Behalf Of
Joseph Zeglinski
Sent: Tuesday, September 03, 2013 11:42 AM
To: ap-gto@...
Subject: [ap-gto] Re: Meridian Flip - Flop & Flexure compensation factor

Hi Rick,

You may be quite right.

Perhaps I, like many, have been avoiding admitting the obvious. I
haven't needed the more advanced tools like TSX, but I may have to take that

option, if the APCC isn't available before the snow hits.

One thing about "modelling" however. I think it is more relevant for
"fixed" position installations, to perfect sky pointing accuracy.
But, for those that have portable setups, having a predefined meridian flip
correction factor, to compensate just the mirror flop and flexure errors,
might be a good alternative for the additional step of recreating a new
model after every setup, which adds orthogonally correction, to the overall
solution. For portable systems, having a basic flop/flex correction just
might be sufficient.


-----Original Message-----
From: observe_m13
Sent: Tuesday, September 03, 2013 1:17 PM
To: ap-gto@... <>
Subject: [ap-gto] Re: Meridian Flip - Flop & Flexure compensation factor

Sounds to me like a classic case of the scope being slightly non-orthogonal
to the mount. TheSkyX with TPoint or MaximDL with MaxPoint (and PinPoint) do

what you are asking through the computer run software. APCC will be able to
do it too.

The keypad won't. It is standalone and doesn't have modelling software in

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