Re: Erratic parking of the mount

Dale Ghent

Bruce, one other thing to check is the clock on your computer to ensure it is accurate. In the Astro-Physics ASCOM driver, make sure that "Sync PC clock to mount" (I think that's the name of the option, from off the top of my head) is selected.

Pointing errors like this can be caused by an inaccurate clock setting in the mount controller. By ensuring that your computer's clock is accurate and enabling the option to sync your PC's time to the mount in the ASCOM driver, you will get an accurate clock in the mount's controller each time you operate it.

Since you mention guiding and so-on, I presume you are imaging and not using this for visual. Once you make sure all that is in order, I would slew the telescope to a nice spot of the sky, plate solve that spot in the sky, and sync the solved coordinates to your mount. You should honestly be good to go from there on out including later sessions.

So, in summary, the absent any mechanical issues (inaccurate polar alignment, clutch slippage, etc) an:

1. Accurate PC and mount clock
2. An accurate notion in the mount computer of where it is pointing
3. An accurate-enough lat/long configured

...will return you to a perfect park position each time, and prevent you from having to manually recenter or nudge your telescope because it's grossly off the selected coordinates. Your mount knows where it is, what time it is, and where it is pointing. The 3 key ingredients.


On Feb 13, 2020, at 12:54 PM, Bruce Donzanti <> wrote:

Great- good to understand what is probably causing this and that a solution is forthcoming.

Thank you

On Feb 13, 2020, at 12:05 PM, uncarollo2 <> via Groups.Io <> wrote:

Usually, this is fine but every now and then I noticed the scope does not park in position 4 exactly as it should (i.e., the RA axis is slightly off level).
All sky positions are calculated from the previous object that you did a Recal on. That includes park positions. If the last object that you Recal on is off by 1 degree when you pressed Recal, then every object that you go to including all park positions will also have that 1 degree error.

Your errant Recal could be the result of an error on your part or deliberate if you wanted to center a nebulous object and then did a recal on it. What you might think was the center might not be the center as defined in the database, so that throws off everything else following that move.

We are working on changing the way parks are generated so that they are not affected by errant recals or syncs. The software will be available for the CP4 and will be standard in the Mach2 CP5 controllers.


-----Original Message-----
From: Bruce Donzanti <>
To: main <>
Sent: Thu, Feb 13, 2020 5:42 am
Subject: [ap-gto] Erratic parking of the mount

In my permanent setup, I use SkySafari 6 Pro as my planetarium program to slew my AP1100 with no issues (connected to the GTOCP4 via RS232). It parks and unparks from position 4 with no issues. I also use PHD2 for guiding by linking it as required to the mount to my capture and live viewing software (SGPro or SharpCap) which are connected to mount via USB with no issues. However, I have had random problems with shutting down the system. I first park the scope using SkySafari 6 Pro and then close PHD2 followed by the capture software. Usually, this is fine but every now and then I noticed the scope does not park in position 4 exactly as it should (i.e., the RA axis is slightly off level). I can't seem to figure out what is the cause as it is very infrequent but annoying as it misaligns the scope for the next time I startup Skysafari 6 Pro to slew to an object (i.e., the mount is lost and I need to realign). Any thoughts as to what is going on? Is my shutdown sequence wrong?


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