Re: AP900 CP4 with ASIAIR - need some guidance

Kevin Cook

Hi Dan - I don't know if this will help in your situation, which is a little different than mine. I am using a Mach 1 mount with the CP3 version.  The mount is connected to my ASIAIR PRO via an RS232 cable (on the CP3 side) to the ASIAIR (regular USB connector).  When it works, it works like a charm for polar alignment, plate solving, and guiding.  Where it gets squirrely seems to be when I power up the mount first, then power up the ASIAIR - that is when the mount motions go seriously astray, sometimes starting with that first polar alignment rotation of the RA axis.  It seems as though the ASIAIR does not know when the home position (Park 3 for me) is, so all subsequent motions are out of whack. Things go much better when I power up the ASIAIR first, make sure I hear it beep that it has set up its little local wifi network, then I power up the mount and open the ASIAIR app.  No guarantees it will resolve your issues, but give my recommended startup sequence a try.

Kevin Cook

On Fri, Jun 3, 2022 at 5:28 AM Dan_Paris <danysra@...> wrote:
   Hi everyone,

since yesterday I am a happy owner of an AP900 with CP4 upgrade. What a beautiful an impressive mount! 

Coming from a Skywatcher AZ-EQ6 driven by an ASIAIR using EQMOD, I tried to use the AP900 in the same way.

I connected the ASIAIR to the CP4 with an USB cable, an turned everything on. After choosing "Astro-physics CP3/CP4" in the mount menu of the ASIAIR, the mount was instantly recognized and reacted to the arrow buttons on the phone screen. So far so good.  I then tried to simulate a full imaging session.  Everything eventually worked but there was some oddities:

  1. When I ran the polar alignement procedure, after the first plate solve the mount moved in RA (as it should) but the displayed angle stayed at 0° and the motion stopped then midway. To remedy this I had to first point the mount away from the pole, take a picture, sync the mount, come back to park 3 position (all with ASIAIR), before launching PA.
  2. I sent a GOTO command with the ASIAIR to M13, which was then 1h30m east of the meridian. However the mount moved in the "wrong" direction and ended up counterweight up (fortunately the scope cleared the mount - but not by much). I sent after that another GOTO command to M51 (which was about 2h west of the meridian) and this time the mount was in the standard position, i.e. counterweights down.
  3. I tried to calibrate autoguiding. The West steps were as they should (small), but when it reverted to East, the mount made a very large motion (enough to put the guide star out of the FOV). I tried then to enforce guiding speed 1x with the GTO keypad first, it worked but only to some extent (the star was lost but eventually found).
I managed to take few autoguided frames and the results are very encouraging - significantly tighter stars than with my previous mount. 

I am wondering whether there are extra steps or settings that would make the dialog between the ASIAIR and the CP4 smoother ?

Thanks for your help,


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