Re: New AP1100, indoor practice, lots of little questions

W Hilmo

My suggestion is to regard “find home” as a recovery tool.


In about 10 years of using Astro-Physics mounts, I’ve never actually used the “find home” feature.  In my normal workflow, I have my automation set to park the mount in Park 4 at the end of a session.  If I am going to remove the OTA, I manually park it at Park 3.  And as Roland says, there’s no need to park the mount at all.  Just power it down when you are done.  I have my mounts configured to unpark from “last parked”, so when I want to star a session, I just turn them on and go.


I have had a handful of cases in that time where I managed to get a mount lost.  It was never in a normal workflow.  Most of the time, it was when I was experimenting with some unreleased mount control software.  Since I’m not a remote imager, I just recovered the mount manually, although “find home” would have worked as well.


I also never loosen the clutches, unless I’m recovering from a lost situation.


Regarding sync versus recalibrate, recalibrate is your friend.  Recalibrate works like a sync on most other mounts.  Essentially, it says “forget where you think you are pointed, you are pointed here.”  Sync is similar, but adds one more nuance.  Specifically, sync is just like a recal, but in addition to saying “you are here”, it also says “and the counterweights are down”.  It’s not immediately obvious why you would want to tell the mount whether the counterweights are up or down.  The reason is that, for any position in the sky, there are two ways that the mount can point there.  One way is what we usually see, with the telescope above the mount and counterweights below.  But you can also point at any position in the sky with the counterweights above the mount and the telescope below.  An Astro-Physics mount is very flexible, and will point with the counterweights up if you want it to.  The purpose of a sync, as opposed to a recal, is so to tell the mount that the counterweights are down.  The gotcha here is that if you are pointed near the meridian, the counterweight shaft is nearly parallel to the ground.  If you are not careful, and do a sync near the meridian, you might accidentally do the sync with the counterweights imperceptibly up.  When that happens, the mount will always slew with the counterweights up and scope down.


My suggestion is to avoid doing a sync, ever. The exception is if you are recovering from being lost.   I can’t remember the last time I did a sync.  The ASCOM driver has a feature to convert “sync” commands to “recal”.  The feature is enabled by default, and you should probably never disable it.


I hope that this makes sense,



From: <> On Behalf Of ap@...
Sent: Saturday, July 31, 2021 5:16 PM
Subject: Re: [ap-gto] New AP1100, indoor practice, lots of little questions




@Roland said:


  • You actually do not ever need to park the mount. You can turn the power off any place in the sky. When you resume the next session, the mount will know exactly where it is because the encoders are absolute (as long as the clutches are never moved because the encoders on the 1100 are not attached to the clutches). Simply unpark the mount from its present position. I do this all the time and most often never really park the mount.


Thanks, I understood that.  I want to park because it’s an easier load/unload point to disassemble the OTA.  Also, Park 2 will be less likely to accumulate rain or dew if it parks due to some failure while imaging and I’m asleep.


  • If you were to recal or sync the mount on a known star the 3D model would display correctly. 


See that’s where I am confused.  The mount and APCC seem to think it is right (or close).  I fired up Pempro (I’m still in daylight) and started the polar align, which goes to 5 west of meridian at dec 0.  The mount slewed to what looked like that position exactly.  The Telescope Position in APCC showed the red dot in the right place.  Wouldn’t a sync actually just refine this from a plate solve?  The 3D model is almost upside down, it’s not off a few degrees . Or is it just plain completely wrong until at least one sync is done?


Can I impose also: Sync vs Recal?




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