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SkySafari Error "Command Failure - Your Alignment Target Is Too Far The Telescope's Actual Position..." (Solution: Use Alignment Stars Further Apart - Read On!)

Calerner

October 22, 2018 10:31

Answered

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I recently installed amt 102 encoders and nexus II on an equatorial mount. I have SkySafari 6 plus on an iPhone SE. I've had some success, but more failures when trying to use alignment stars to initialize the setup.  The main problem is getting SkySafari to consistently "accept" the second alignment star and not give a "command failure" saying the alignment target is too far from the telescope's actual position.

Below is a link to a series of annotated screenshots from my most recent experience. (The screenshots were made when running SkySafari 4, but I recently installed SkySafari 6 and the same things happen)

https://docs.google.com/document/d/1VBO5ZKyxlCZduhhEPkAT0H8u5deAU1QOu9IdnrrFMjE/edit

I have tried aligning on stars relatively close and aligning on stars that are relatively far from each other.  I have tried aligning to stars on the same side and tried aligning to stars on opposite sides of the meridian.  I can't tell a pattern for when it will accept the second star and when it will say it's too far away.  Sometimes the second star may be 2 degrees away from the virtual telescope position and it will accept it; sometimes it's about 1/2 degree away and won't.

I'd love a better understanding of what might be going on.  Thanks.

Charles

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3 comments

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  Keiron Smith November 02, 2018 19:06 Official comment

  Here was the resolution of the problem…

  Unexpectedly, he was picking two stars to align on that were very close together in RA.  SkySafari cannot build a good alignment model with that.  SkySafari was returning an ambiguous error code which in this case said the star was too far from its expected position.  We have changed the error code and now SkySafari will display the message: 

   

  “An accurate alignment model cannot be constructed using this star.  Please align on a different target further away in RA.”

   
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  Keiron Smith October 22, 2018 16:47

  Please Start Here:

  SkySafari Error Message: "Your alignment target is too far from the telescope's actual position.  Please make sure you selected the right alignment target".

  Problem: Generally when you get this message, it means your initial alignment is not accurate.  When that far off, doing a local Align will not be able to correct the original alignment model. 

  Our rule for your scope type is that the object needs to be within 1º from where we think it should be based upon the alignment model in the mount.  If it is further than 1º away then there is probably some more serious problem; i.e:
  
  1. You have selected the wrong object to align on (e.g. you were centered on Jupiter but had some other object selected when tapping Align).
  2. The initial alignment model is very inaccurate.
  3. The time in the mount is different from the time in SkySafari.  A planet's RA/Dec is dependent on the time (unlike stars) so this error would really only happen with solar system objects.
  
  When you tap the Align button, we store an offset from where the mount thinks it is pointing to where you are saying it is pointing.  We apply that offset when doing GoTo or when showing the scopes reported location on the screen.  It has been our experience that if the offset is greater than 1º then this doesn't work well.

  Solution: Align again, with a detailed focus on accuracy.

  Thanks!

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  Stephen Wheatcraft November 02, 2019 22:52

  I am getting this error while trying to align with the Sun. I read your forum article on this, with the 3 possible causes. I know I have selected the Sun, and so it must be cause (2) or (3). I am using a Celestron NexStar Evolution, so Celestron WiFi. So SkySafari should be sending the correct time to the scope. So it must be (2), initial alignment model is very inaccurate.

  So, is there a way to clear out the alignment model in the scope?