HEQ5 Pro 'caution previous NPE is applied'

[Dave2292]

Hello and thanks for coming to this post.

So I currently have a problem with my skywatcher Heq5 Pro mount, after I do a 1, 2 or 3 star align and the handset says successful alignment it gives me this 'caution previous NPE is applied'. 

It then goes back to the start of the start alignment where I have to chose either a 1, 2 or 3 star alignment,  if I ignore this and try to go to an object it is completely off target.

I have tried factory resetting but that hasn't helped.

 

Any help is appreciated, thanks

[malc-c]

If you google the message you'll find that its some message related to the calculation based on calculated discrepancies between the axis - Here's one explanation I found.

Quote

NPE is "Non perpendicular error" and is used ( somehow ?? ) with CE "Cone error.

NPE is supposed to account for any errors in orthogonality between the RA and DEC axles,

Both CE and NPE can now be entered via the Hbx.

CE is supposed to be calculated and overwritten if you do a three star align but i have no idea how they measure NPE.

And another, more detailed on Cloudynights forum

Quote

If your only concern is the caution message, you can safely ignore it. It is completely normal. Below is my understanding of the message.

When you do a three star alignment, the mount (HandBox, actually) tries to figure out three things: 1) the general orientation difference between where the mount's RA axis is pointed and the North Celestial Pole (the polar alignment error), 2) how much Cone Error you have (the degree of parallelism between the telescope's optical axis and the mount's RA axis), and 3) the Non-Perpendicularity Error (the amount by which the RA and DEC axes of the mount differ from exactly 90°). When you perform the three star alignment, the mount (HandBox) stores the calculated values for Cone Error and NPE in memory for future use.

When you do a one star or two star alignment, the mount cannot figure out all of the above. It can only calculate the amount of polar alignment error based on the one or two stars you used. So, if you have previously done a three star alignment and for this session do a one or two star alignment, the mount simply recalls the data for CE and NPE from the values it stored from the last time you did a three star alignment. I does however warn you that it is using old data. That is the warning about "Previous NPE Applied".

NPE doesn't normally change between sessions. With a good firm mounting of the scope to the mount saddle dovetail, CE can change a little from one observing session to the next but not by a lot each time. Thus it's perfectly valid to save and reuse CE and NPE from one session to another.

If the cautionary message bothers you or you wish to refresh that data at the beginning of each session, just always do three star alignments. If you use different scopes on the mount, you should probably do a three star alignment anyway since that will refresh the stored value of CE as each scope may have a different CE value.

 

So basically the message can be ignored

[AstroMuni]

4 hours ago, Dave2292 said:

It then goes back to the start of the start alignment where I have to chose either a 1, 2 or 3 star alignment,  if I ignore this and try to go to an object it is completely off target.

Just to understand more clearly, you are saying that it successfully completes the alignment and gives a warning message. But after that the objects are off target. Is this correct?

When an object is off target, how far off is it to actual position? If its close but not on the dot, then that happens depending on which stars have been used for alignment.
 

[carastro]

I have an HEQ5 and have never had this message, however my mount is a few years old so may have different software.   To be honest l PA accurately (with polemaster) but sometimes it doesn’t GOTO my alignment star either. Yet another nights it is spot on???!!  
 

l stopped doing any more than a 1 star alignment a long time ago as l have cone error and trying to align on two sides of the Meridian just causes more problem than simply doing  a 1 star alignment.   I then goto a bright star near my target and sync. 
 

Carole

[Earl]

Have you tested the mount with another handset or eqdir ? 

[Dave2292]

9 hours ago, malc-c said:

If you google the message you'll find that its some message related to the calculation based on calculated discrepancies between the axis - Here's one explanation I found.

And another, more detailed on Cloudynights forum

So basically the message can be ignored

I would ignore it if the mount pointed correctly at my target after doing the star alignment.

5 hours ago, AstroMuni said:

Just to understand more clearly, you are saying that it successfully completes the alignment and gives a warning message. But after that the objects are off target. Is this correct?

When an object is off target, how far off is it to actual position? If its close but not on the dot, then that happens depending on which stars have been used for alignment.
 

yes the alignment is successful, the 2nd and 3rd stars are pretty much bang on, I get the warning and then it takes me back to the star alignment but if i choose to ignore this and try and slew to a target, it isn't even close.

It's strange I had recent issues with Cartes du ciel. where I would sync on a star, slew to my target for the night and take a test shot but it would so far off.  It was working fine for a good year with Cartes du ciel with a lynx astro cable and a year before that using the handset.

5 hours ago, carastro said:

I have an HEQ5 and have never had this message, however my mount is a few years old so may have different software.   To be honest l PA accurately (with polemaster) but sometimes it doesn’t GOTO my alignment star either. Yet another nights it is spot on???!!  
 

l stopped doing any more than a 1 star alignment a long time ago as l have cone error and trying to align on two sides of the Meridian just causes more problem than simply doing  a 1 star alignment.   I then goto a bright star near my target and sync. 
 

Carole

It is bizarre , ive had the mount for a few years now and done lots of astrophotography using either the handset or connected to my laptop using a lynx astro cable. Just when doing astronomy I like to use the handset.

2 hours ago, Earl said:

Have you tested the mount with another handset or eqdir ? 

well before my laptop had some issues, it was actually acting very strange when using Cartes du ciel (after a year of perfect working). Thinking about it now it was probably doing the same thing but not as bad, I would sync to a star and then I would  slew to a target but it would be off by so much I could not see the target at all or recognisable stars in a test shot. I will be trying again tonight with Cartes du ciel and see if it is accurate.

[Clarkey]

20 hours ago, Dave2292 said:

caution previous NPE is applied

You should be able to go into the handset and reset the NPE value to 0 in the settings menu.

[AstroMuni]

11 hours ago, Dave2292 said:

It's strange I had recent issues with Cartes du ciel. where I would sync on a star, slew to my target for the night and take a test shot but it would so far off.  It was working fine for a good year with Cartes du ciel with a lynx astro cable and a year before that using the handset.

Thats interesting. If you have the lynx astro cable then you should be able to use platesolving to get accurate go-to positioning. Check if some parameters have changed such as incorrect date or location.

[Dave2292]

On 12/07/2022 at 09:05, AstroMuni said:

Thats interesting. If you have the lynx astro cable then you should be able to use platesolving to get accurate go-to positioning. Check if some parameters have changed such as incorrect date or location.

Okay so this is bizarre but it seems to be working fine now, not really sure what happened but thank you for the help anyway man.