Re: Dec limit in Mach2

Ray Gralak

Hi Luca,

I scanned your logs and I don't see any "motor stall" errors, but I do see that the mount was hitting a declination limit.

On APCC's AE tab, you might try disabling Dec Limits if it is enabled.

-Ray Gralak
Author of PEMPro
Author of APCC (Astro-Physics Command Center):
Author of Astro-Physics V2 ASCOM Driver:

-----Original Message-----
From: [] On Behalf Of Luca Marinelli
Sent: Saturday, January 30, 2021 4:04 PM
Subject: Re: [ap-gto] Dec limit in Mach2

On Sat, Jan 30, 2021 at 06:31 PM, Roland Christen wrote:

1) Make sure that your mount is balanced.
2) make sure that all 4 clutch knobs are tight. When they are loose the mount may stop slewing which
triggers a motor stall.

Unless you have limits set up, the mount will not reach limits until it is totally upside down.

The mount is also never lost unless you send a faulty recal.

If you do lose the position due to faulty recal, the mount's true position in the sky is always recovered when
you send it home.

If you are unparking the mount from previous position, you do not have the latest APCC version for the
Mach2. The Mach2 does not need to be told to unpark from any position because it has absolute encoders and
always knows where the axes are pointed. The correct version of APCC will not prompt you to unpark the mount
from any position.


Thank you, Roland

I am just as perplexed by this behavior and am inclined to agree that there has to be some leftover from the
Mach1 setting that is messing me up.
To your points:

1) and 2) The optics is balanced and the clutches are hand tight. The mount is carrying a FSQ106, so nothing
heavy. I don't think I need to tighten the clutches with a hex wrench.

I don't have limits set up. As you can see in the screenshot I attached, when APCC gave the error Dec limit was
reached, the mount was pointing to the Northwest, on it way to Park 3. I don't what Dec limit it is referring to. As I
said, sending it home works, but I don't think I should be sending the mount home a couple of times a session.
Obviously, I am doing something wrong or there is a setting that is preventing it from working correctly.

I am running APCC Pro version, firmware VCP5-P02-08, encoder version A02-08 (see attached
screenshot). I don't think there is a more recent version of the software. When I launch APCC Pro, the mount
initialization screen includes the field Unpark from: Last Parked. Should it not? Is this mount initialization screen
incorrect for the Mach2 (again see attached screenshot).

Incidentally, tonight I launched the imaging run without first sending the mount home and it did not give the error.
We'll see if it also parks the mount successfully in the morning when it's done.

Thanks a lot,


Join to automatically receive all group messages.