SynScan Update - NP error

[Jammy]

Hi there, I've just updated my SynScan from version 3.35 to 3.37 and I've noticed a couple of changes.

Firstly, you now have to enter your elevation (not sure if that makes any difference).

Secondly, there are a couple of new features added.  Cone error and NP error.

I know what cone error is, but I have no idea what NP error is?

There is nothing in the latest skywatcher manual to explain it.

Does anyone know what it is, and if I need to bother with it?

Version 3.35 was working fine, I only updated out of curiosity       

[ronin]

Non Perpendicular Error apparently.

Old post on SGL a few months back.

Came out in V3.36, the one you didn't load.

Seems they can be set manually to 0.

[teleskopjo]

Would that account for non level piers

[ronin]

From the description I read elsewhere it has to do with the Dec angle difference, actual and what the scope uses, so I guess it is. Seems that it is determined when 3 star alignment is performed, although would have thought it was also done at 1 and 2 star alignment to some extent.

Appaently it is covered in the manual that was relased for V3.36, but real astronomers don't read manuals . Except it seems one lone Australian astronomer that loaded V3.36 then for some unknown reason downloaded the manual, read it then was able to tell the others in the thread what it all was :eek: . I can only think that they were in the Australian sun for too long.

Likely always been in there in one form or another but they now tell you how bad it is, likely in the hope that seeing a value people will try and start out a bit better.

[Jammy]

Thanks for the replies, but I was still none the wiser as to what NP was until I found this:

http://www.wildcard-innovations.com.au/geometric_mount_errors.html

From that I understand NP as being the accuracy of levelling your mount.

As a surveyor, I tend to do it without thinking 

[jambouk]

Does it really mean how level the tripod is? My reading of that is that NP reflects the angle between the RA and the Dec...

[Jammy]

To be honest, I'm still not sure!

[jambouk]

The dec axis is supposed to be at right angles to the polar axis; i think the NP error is the amount this is out. I'm not sure how one works out how big their NP error is though, and i'd have thought a three star alignment would compensate for this as it does to reduce the impact of cone error on pointing accuracy. I suspect for most mounts, the NP is pretty small, though cone error can be quite large.

[Jammy]

I see what you mean now.  The only thing I don't understand is how the mount distinguishes between cone and NP error... but I'm happy not knowing!! 

[jambouk]

If you could tell the mount exactly what the cone error was, then might the remaining error in pointing accuracy be down to NP error? I have no idea either, but it is interesting.

James

[dph1nm]

Does a 3 star alignment actually update these values? I still get warnings saying previous values applied, or something like that, even when doing a 3 star alignment.

NigelM

[jambouk]

I suspect this alert relates to the NP error as the manual suggests a 3-star alignment results in the Cone Error being updated in the handset,

James

[jambouk]

From the manual:

"Note: If the value of CE or NPE entered in the hand control is not 0, the hand control will give a reminding message “CAUTION: Prev. NPE, CE applied.“ at the end of the alignment routine. User should make sure that the stored CE and NPE parameters are correct for the current system setup; otherwise, these value should be set to 0."

[dph1nm]

Which begs the question, if you set them to 0 do they get overwritten when you do a 3-star align (which is supposed to correct for CE) or does the software assume your CE is 0? Makes no sense to me.

NigelM

[wookie1965]

Hi,

          Has anyone found a fix for this I have just got aEQ5 Pro Goto and I`m having problems, first time I used it after setting up as instructed did a 2 star alignment but objects were not in the middle and the more objects I went to they drifted out of the eyepiece. Next time I did a 2 star alignment I got the caution previous NPE Applied, I then reset the handset to factory settings did a 3 star alignment and everything went well, took the scope out last night did 2 star alignment got the error ignored it went to a few objects first 3 dead centre next 2 over to the right last M57 not even in eyepiece any help much appreciated.

Paul