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Re: Servo Failure ?

Ned Smith
 

Can these voltages be read even though that motor is blinky?
What is the meaning of M.E.A and S.E.AA?
These are the motors I use to operate my 25' dob @ 19v.

On Tue, Jun 28, 2022 at 5:08 PM Don W <westergren@...> wrote:
Hi Ned,

Physically checking the connections may not find the problem if there is no signal.  Check with a volt meter (easy to do with the screws on the connector to the Servo II).  The A and B signals should alternate between near zero and near 5 volts with tuning very slowly.  Fast motion, both A and B should show about 2.5 volts.  If you don't have those voltages then that is the problem - a broken wire or connection or maybe the encoder.

Don W.



--
Ned Smith


Re: PointXP terms explained

dan adi
 

If you have a list of the terms and what they mean it would be perfect. Thank you


Re: PointXP terms explained

Don W
 

Hi Dan,

OK, I found two notes that were private messages to me from Dave Rowe and Dan Gray.  These apply to the original PXP2.

Dan's Note:
PXP ERROR TERMS

What are the mount error terms?

1. Cone (Z2): This is a fabrication error. It is sometimes called Collimation error, as it is the error between the optical axis of the scope, and the altitude (declination) axis.

2. Hub (Z1): This is a fabrication error. It is the error between the azimuth (RA) axis and the altitude (declination) axis.

3. Dec Imbalance: As the scope moves in Altitude (declination), the scope may flex. Also will correct for a non-centered encoder.

4. RA Imbalance: As the scope moves in azimuth (RA), the scope may flex. Also will correct for a non-centered encoder.

5. Dec Transvers: Same as #3, however it is as if a weight was on the side of the scope.

6. RA Transvers: Same as #4, however it is as if a weight was on the side of the scope.

7. Dec Droop[cos]: Corrects for the Cosine of the Declination (or altitude), as your secondary cage or camera flexes position during different altitudes or declination.

8. Dec Droop[Sin]: Same as 7, but the Sine instead of the Cosine

9-12. Alt Sin/Cos. These parameters can have the same effect as flattening the bottom of your azimuth axis. It can help an alt/az scope more than an equatorial scope.

Now Dave's notes:

Greetings,



Keeping it as simple as possible, here's a basic description of the error terms in PointXP, and some other useful information. In the following, Phi is either the RA axis or the Azimuth axis. Theta is either the Dec axis or the Altitude axis.


Encoder Offsets: The error in the zero position of the encoders.


Axis Misalignment: For an equatorial: North is the error of the polar axis to the north, and West is the error of the polar axis to the west. If both number were positive the axis would have to be moved to the south and east to align the polar axis. For an alt-az: North is the error of the azimuth axis to the north, and East is the error of the azimuth axis to the east. Both errors are relative to the local Zenith. Typically one does not try to align the azimuth axis to the Zenith.

Axis Non-Orthogonality: Cone is the non-orthogonality of the optical axis with respect to the Theta axis, i.e., the Declination axis for an equatorial, or to the Altitude axis for an Alt-Az. Hub is the non-orthogonality of the Theta axis with respect to the Phi axis.


The rest of the terms model errors of each axis with respect to harmonics of the position of its own axis or the other axis. For example, consider term 31. It models the error in Theta as a function of sin(3*Phi). To form a complete set, all angular errors must come in sine, cosine pairs. Thus, term 31 is accompanied by term 32, cos(3*Phi). Of special note are terms 7 and 8, 9 and 10. Terms 7 and 8 model the de-centering of the worm gear or axis encoder or friction drive of the Theta axis. Terms 9 and 10 model the de-centering of the Phi axis encoder or drive.


PointXP exactly models the Encoder Offsets and the Axis Misalignment. All other terms are modeled as small error perturbations. If any error numbered 5 or higher is larger than about a degree, a small residual error in the model will result. For a 1 degree error, the modeling error will not be larger than about 1 arcsecond. For a 2 degree error, the modeling error could be as large as 10 arcseconds.


It's quite important to select either "Recommended for Equatorial" or "Recommended for Alt-Az" in the Model Parameters form based on the type of your mount.


The Model Sensitivity is a mathematical construction that estimates how sensitive each error term is to small changes in the other terms due to unavoidable, small errors in the input data. It's been found empirically that for most situations if this parameter is less than 300 a robust model is calculated. PXP will not enable terms if it causes the Sensitivity to be larger than the Maximum Sensitivity input parameter, found on the Model Parameters form. I recommend that the Maximum Sensitivity be set to 300.


Dave
 Saturday, March 10,2012  6:22 AM


Re: PointXP terms explained

Don W
 

Hi Dan,

The Version 90A release notes have a description of PXP2.  You can find it at http://www.siderealtechnology.com/SiTechExeReleaseNotesVersion0.90.pdf

PXP3 works the same way, but has all-sky capability and is probably a bit more accurate.

I have a list of all the terms somewhere on my computer - I have to search them out.

Don W


Re: Servo Failure ?

Don W
 

Hi Ned,

Physically checking the connections may not find the problem if there is no signal.  Check with a volt meter (easy to do with the screws on the connector to the Servo II).  The A and B signals should alternate between near zero and near 5 volts with tuning very slowly.  Fast motion, both A and B should show about 2.5 volts.  If you don't have those voltages then that is the problem - a broken wire or connection or maybe the encoder.

Don W.


Servo Failure ?

Ned Smith
 


I have been operating my Servo II for  several years without issue.  Last night the AZ motor went "blinky" and ran away.  This usually means one of the wires connected to the optical reader is undone.  Checked all connections today and found all good.
The AZ motor LED Is on "slow blink" mode.  The LED stays on for 7 seconds then off for 7 seconds ad infinitum.  Very different from Blinky mode.
I had this several years ago but I can't recall how to fix it.

--
Ned Smith


PointXP terms explained

dan adi
 

Is there a manual or documentation about PointXP?
It would be nice to know more about what the model terms mean. It would be easier to troubleshoot your setup.
I searched on Planewave site but no details about PointXP.
This was a nice read about Tpoint : https://sites.astro.caltech.edu/~srk/TP/Literature/Wallace_Telescope_Pointing.pdf


Re: Model making

Chris Waters
 

Thanks folks,

Joshua:       Yes I still had my Mewlon 210 in the scope info,easily fixed once I found scope info again,many years!

Jim     : yes I had cleared the model

Dan    : as  per Joshua's suggestion and yes I did have the correct camera properties set.

Now another clear night is required,you need all the sky to build a model.

Chris

On 26/6/22 21:34, Joshua Hufford wrote:
My first thought would be since the focal length has changed (assuming that it would have with the larger scope) your FOV and image scale has changed so you are no longer able to plate solve. I would make sure that your optics and camera settings are correct.

Josh

On Sun, Jun 26, 2022 at 8:30 AM Chris Waters <muletopia@...> wrote:
Learned people,

In the past I have made 40 pint calpoint models with ease. That was with
a Takahashi Mewlon 210. The error plot was horrendous due to mirror flop.

So a year long search finally let me buy a second hand Mewlon 250, no
more mirror flop.

Tonight I tried to make a model and was presented with the message


image <> original image size.

  So the process was aborted. I guess that there is some where that
something has to be reset.

Chris







Re: Model making

dan adi
 

Make sure you have scope aperture and focal length introduce in sitech.exe.
Make sure you introduce pixel size of your camera.
Make sure the catalog path is correct.
Clear previous calibration points.
I  tried with a SCT long time ago, the mirror was everywhere ... Now I use a refractor but didn't try a model. I guess it would be better with a refractor.


Re: Model making

jimsgtastro
 

Did you clear old calpoints before starting the new model?

Jim Sgt

On Sun, Jun 26, 2022 at 7:30 AM Chris Waters <muletopia@...> wrote:
Learned people,

In the past I have made 40 pint calpoint models with ease. That was with
a Takahashi Mewlon 210. The error plot was horrendous due to mirror flop.

So a year long search finally let me buy a second hand Mewlon 250, no
more mirror flop.

Tonight I tried to make a model and was presented with the message


image <> original image size.

  So the process was aborted. I guess that there is some where that
something has to be reset.

Chris







Re: Model making

Joshua Hufford
 

My first thought would be since the focal length has changed (assuming that it would have with the larger scope) your FOV and image scale has changed so you are no longer able to plate solve. I would make sure that your optics and camera settings are correct.

Josh

On Sun, Jun 26, 2022 at 8:30 AM Chris Waters <muletopia@...> wrote:
Learned people,

In the past I have made 40 pint calpoint models with ease. That was with
a Takahashi Mewlon 210. The error plot was horrendous due to mirror flop.

So a year long search finally let me buy a second hand Mewlon 250, no
more mirror flop.

Tonight I tried to make a model and was presented with the message


image <> original image size.

  So the process was aborted. I guess that there is some where that
something has to be reset.

Chris







Model making

Chris Waters
 

Learned people,

In the past I have made 40 pint calpoint models with ease. That was with a Takahashi Mewlon 210. The error plot was horrendous due to mirror flop.

So a year long search finally let me buy a second hand Mewlon 250, no more mirror flop.

Tonight I tried to make a model and was presented with the message


image <> original image size.

 So the process was aborted. I guess that there is some where that something has to be reset.

Chris


Re: Pec shape

Glauco
 

On 21/06/2022 22:23, Don W wrote:
Hi Glauco,

I am not an expert with AutoPEC, but I would say that the red ave=0 is bad.  I think you need to run the autoPEC again and follow the instructions exactly.  Each cycle through the PEC will be slightly different, but they should combine into a good average of all the curves.

Don W
_.


To be honest, I've not clear how to read this chart,

but it was done following the instructions.

For the AutoPEC procedure there is no complexity at all.

what could have been done wrong?


Gla



Re: Precession before sending J2000 coordinates to SiTech with ASCOM

Che
 

well thats what I thought.   But you did say turn off dec corrections. Chalk it up to the wording I guess.  Dont worry, my dec will remain on   Quote "The same situation applies to guiding - SiTech always corrects the RA guide corrections for the local Dec (applying a Cosine correction) so you need to turn off Dec corrections in any guide software."
 All good
Che


Re: Precession before sending J2000 coordinates to SiTech with ASCOM

Don W
 

Hi Che,

NO, NO, NO.

I didn't say turn off DEC.  I said that SiTech applies a cosine of the Dec as a correction to the RA (to make larger RA corrections at high Dec.  in SiTech, you can not turn that off, so make sure you don't turn the Dec CORRECTION on in PHD2 or other guider programs.  This is another case where you don't want two programs both applying a correction.

Don W


Re: Precession before sending J2000 coordinates to SiTech with ASCOM

Che
 

I never knew you were supposed to turn off dec guiding in the guiding software.   I use PHD2 and often struggle with the dec guiding.  I will have to try turning it off 


Re: Precession before sending J2000 coordinates to SiTech with ASCOM

Don W
 

Hi Dan and Bruce and all,

Nutate and Aberation are factors in pointing your telescope/mount.  Like all factors, they should be included ONLY once.  These are not "Big" factors, but they are real.  When you do a GoTo, whether you use them or not, your FOV will probably always "see" your target just fine.  But as Dan's note shows, Prism includes these corrections, so using Prism requires turning these corrections off in SiTech.  You do not want any corrections applied twice.

The same situation applies to guiding - SiTech always corrects the RA guide corrections for the local Dec (applying a Cosine correction) so you need to turn off Dec corrections in any guide software.

Don W


Re: Precession before sending J2000 coordinates to SiTech with ASCOM

dan adi
 

Are nutation, aberration important only for modeling? After digging into Prisms v.10 manual in french, I came across their Tpoint modeling option that states:

" A pointing model does not take into account problems independent of the instrument such as the atmospheric refraction of the star, the proper motion of the star, the correction of precession and nutation, the taking into account of the annual aberration: these last parameters are automatically corrected when PRiSM sends the coordinates to the instrument (PRiSM does not directly send the 2000.0 coordinates of the object but the rectified coordinates of all these parameters). Therefore, all internal corrections of the mount must be deactivated when the latter is connected to PRiSM, in order to prevent these corrections from occurring twice!"

From this I understand that Nutate coords and Aberation coords should be left unchecked in Sitech.exe if you plan to use it with Prism. 
 


Re: Pec shape

Don W
 

Hi Glauco,

I am not an expert with AutoPEC, but I would say that the red ave=0 is bad.  I think you need to run the autoPEC again and follow the instructions exactly.  Each cycle through the PEC will be slightly different, but they should combine into a good average of all the curves.

Don W


Re: Precession before sending J2000 coordinates to SiTech with ASCOM

Don W
 

Hi Bruce,

Where are you getting the coordinates that you send to SiTech via ASCOM?  I suggest you go to the ChangeConfig/Misc tab and read the help file about Nutate and Aberraste Coordinates.

Don W

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