Topics

Help finding source of PE fundamentals using PemPro


Tom Blahovici
 

HI.  This might be a question for Howard?
Having had little success with my CP2 on getting PE working with my AP600e, I decided to purchase the CP4.  I collected 5 PE curves with PEC off and found that I had about +- 3.5 arc seconds of PE.  There was the fundamental and two others of interest.  One at 3 and one at 64.  I sent the before and after curves to Ray, and he pointed out that the PEC curve sent to the mount corrected the main source of PE but there was still the 3x and 64x.  He suggested that the 64X was in the gear box and that I should check that the gears are secure.  How are they held in? Could there be wear of the gears? Motor?
As the the 3x, it seems that this is now the major source of the remaining PE however it seems to vary in amplitude.  He suggested that I  might not be able to completely eliminate the 3X frequency as it seems to vary with time. I am not sure if there is a reduction gear involved, or if this is being caused by variations in the worm wheel teeth. Any suggestions in all of this?
Attached are the curves.  The 64x is not shown on the scale but it corresponds completely to the fast changing "sine wave" shown on the raw pe curves.
So, basically, the CP4 with PemPro got me to +- 2.8 arcsec, not much of a fix.
Thanks, Tom


uncarollo2 <chris1011@aol.com>
 

I always include all harmonics that are checked when I generate a PE curve, even if they vary from one tooth to another. I do not include anything over about the 9th harmonic, so the 64th would not be included. The absolute main thing that makes PEM work is that the various curves lie close on top of one another, which in your case they do. That is the most important thing that makes PE correction work.

Rolando

-----Original Message-----
From: Tom Blahovici <tom.va2fsq@...>
To: main@ap-gto.groups.io
Sent: Sat, Sep 12, 2020 2:37 pm
Subject: [ap-gto] Help finding source of PE fundamentals using PemPro

HI.  This might be a question for Howard?
Having had little success with my CP2 on getting PE working with my AP600e, I decided to purchase the CP4.  I collected 5 PE curves with PEC off and found that I had about +- 3.5 arc seconds of PE.  There was the fundamental and two others of interest.  One at 3 and one at 64.  I sent the before and after curves to Ray, and he pointed out that the PEC curve sent to the mount corrected the main source of PE but there was still the 3x and 64x.  He suggested that the 64X was in the gear box and that I should check that the gears are secure.  How are they held in? Could there be wear of the gears? Motor?
As the the 3x, it seems that this is now the major source of the remaining PE however it seems to vary in amplitude.  He suggested that I  might not be able to completely eliminate the 3X frequency as it seems to vary with time. I am not sure if there is a reduction gear involved, or if this is being caused by variations in the worm wheel teeth. Any suggestions in all of this?
Attached are the curves.  The 64x is not shown on the scale but it corresponds completely to the fast changing "sine wave" shown on the raw pe curves.
So, basically, the CP4 with PemPro got me to +- 2.8 arcsec, not much of a fix.
Thanks, Tom


Tom Blahovici
 

Hi
Ok, I also uploaded one curve without the 64x.  It made no difference.  I still get +- 2.8 arc second.  All of this comes from the 3x fundamental even though it is uploaded.  Any ideas what that could be?
Tom


CurtisC
 

On Sat, Sep 12, 2020 at 03:40 PM, uncarollo2 <chris1011@...> wrote:
The absolute main thing that makes PEM work is that the various curves lie close on top of one another, which in your case they do.
So how do you do that?  My curves usually wander slowly up the graph.  My polar alignment is as good as I can get it with PEMPro's Polar Alignment Wizard, and I can take 30 min subs with no noticeable field rotation.


uncarollo2 <chris1011@aol.com>
 


So how do you do that?  My curves usually wander slowly up the graph. 
Perhaps I didn't make things clear. Yes, the individual graphs may wander slowly, but that's simply because of drift. You check the little box for the X or Y that brings the curves down on top of each other. Checking the box essentially compensates for drift and allows just the periodic part of the error to be shown for each of the worm periods. They will lay on top of each other.

Rolando


-----Original Message-----
From: CurtisC via groups.io <calypte@...>
To: main@ap-gto.groups.io
Sent: Sat, Sep 12, 2020 5:12 pm
Subject: Re: [ap-gto] Help finding source of PE fundamentals using PemPro

On Sat, Sep 12, 2020 at 03:40 PM, uncarollo2 <chris1011@...> wrote:
The absolute main thing that makes PEM work is that the various curves lie close on top of one another, which in your case they do.
So how do you do that?  My curves usually wander slowly up the graph.  My polar alignment is as good as I can get it with PEMPro's Polar Alignment Wizard, and I can take 30 min subs with no noticeable field rotation.


Tom Blahovici
 

So, is the harmonic at 3x perhaps due to drift?  It seems to have shifted a bit.  I did not check the boxes for drift adjustment.


Ray Gralak
 

This is not a matter of polar alignment. There are other things, like tube currents and local seeing conditions that can cause weird irregular drift. Irregular drift patterns can affect polar alignment results as well.

If the curves aren't lining up with drift fitting on, then the drift may be complex. However, that won't matter for the purpose of creating a PEC curve. That said, PEC will not give you perfect results if the shape of the curves is different from cycle to cycle.

-Ray Gralak
Author of PEMPro
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of CurtisC via groups.io
Sent: Saturday, September 12, 2020 3:12 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Help finding source of PE fundamentals using PemPro

On Sat, Sep 12, 2020 at 03:40 PM, uncarollo2 <chris1011@...> wrote:


The absolute main thing that makes PEM work is that the various curves lie close on top of one another,
which in your case they do.

So how do you do that? My curves usually wander slowly up the graph. My polar alignment is as good as I can
get it with PEMPro's Polar Alignment Wizard, and I can take 30 min subs with no noticeable field rotation.


Ray Gralak
 

Just in case it is not clear, I did upload 1x and 3x.
The result is that the 3x shifted to 3.1 but it did not seem to reduce it.
Then maybe the frequency might not be exactly 3.0x and thus cannot be corrected by PEC. I suggest you contact Howard at A-P directly, as he probably can look up the mechanical details on the 600 series mounts, which has been out of production for a long time.

-Ray Gralak
Author of PEMPro
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver


-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Tom Blahovici
Sent: Saturday, September 12, 2020 3:41 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Help finding source of PE fundamentals using PemPro

Just in case it is not clear, I did upload 1x and 3x. The result is that the 3x shifted to 3.1 but it did not seem to
reduce it.


Ray Gralak
 

So, is the harmonic at 3x perhaps due to drift?
No, that is extremely unlikely.

-Ray Gralak
Author of PEMPro
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver


-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Tom Blahovici
Sent: Saturday, September 12, 2020 3:39 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Help finding source of PE fundamentals using PemPro

So, is the harmonic at 3x perhaps due to drift? It seems to have shifted a bit. I did not check the boxes for drift
adjustment.


CurtisC
 

On Sat, Sep 12, 2020 at 03:51 PM, Tom Blahovici wrote:
I still get +- 2.8 arc second.
I am envious.


Tom Blahovici
 

I reached out to Howard.  He told me the 64x fundamental is part of the planetary gear train of the motors.  Only recourse is to try another motor, but it is anyone's guess if it will be better.
He is looking up the 3X fundamental to see if anything can be done.


CurtisC
 

Tom, I would be delirious to achieve the PE you're reporting.  I don't understand why you're worried about the fundamental 64.


Tom Blahovici
 

The 64x is not uploaded to the mount.  However, if I can tame fundamental 3 then I have much better than +-2.8
I bought the tools, now I want them to live up to their capabilities. Otherwise, what's the point?