Topics

Precise polar alignment of the azimuth axis


Roland Christen
 

Hi Astronuts,

This first post will describe a precise way to polar align the mount's azimuth. Once that is done, it will not require any further adjustment.The idea is to use the natural geometry of the sky with respect to an earth bound mount to produce a perfectly aligned azimuth. That's the axis that rotates the bottom of the RA axis east and West.

Concept #1) If the scope is pointed straight at the zenith on either the west or east side of the mount, that point will remain stationary as you rotate the azimuth axis. So, if a star is in the eyepiece at that point and you bring it to the center of a crosshair, you can rotate the azimuth axis and the star will stay on the crosshair - at least for some minutes if you are tracking it. However, if you then slew to a star down south along the meridian line, it will deviate either east or west depending if the azimuth axis is too far west or east. The star at the zenith is then a pivot point, and the star down toward the south is your calibration star (or azimuth adjustment star). Bring that one to the crosshair by turning the azimuth adjusters and you are theoretically perfectly polar aligned.

So, the simple routine goes something like this:

1) Using your planetarium program, pick a star near the zenith on one side of the meridian. I like to use a star in the west with scope on the east side. That way it won't migrate across the meridian while doing this alignment step.
2) Bring the star to the center of a crosshair and do a Recal or Sync. MaximDL has a nice crosshair if you want to use an imaging camera for this alignment.
3) Now pick a star down toward the south on the SAME SIDE of the meridian (or north if you are in an upside down hemisphere), and slew to it. The star will appear either east or west of the crosshair, so now just turn the azimuth adjuster until the star is on the centerline of your crosshair. It may or may not be aligned N-S but that is of no consequence. No Recal or Sync is necessary because you did not move it via the motors.

Basically you are done with azimuth, but you can re-check by slewing back to the first star and do these 3 steps again for more precise alignment.

Next post - How to align the altitude axis.

Rolando





John
 

Aloha All,

  Well, I was able to get the new Mach 2 out for the first time over the weekend.  So far so good!  Still re-learning the ropes.

  I need to make a slight adjustment to the RAPAS, plus I wanted to check my current polar alignment using "Roland's GTO Quick Star Drift Method" (which can also be found in the  Mach 2 User Guide, Appendix C, pg 41 [dated Aug 2020]).  I used Sharpcap's polar align routine on my C8 Edge at F/7 with an ASI 1600 camera which puts the image scale at 0.55 arc/sec per pixel.  Last night (and Sat night) as a test, I was actually able to get 8 min unguided images without any oblong stars!  Sharpcap says I'm within 0.5 arcsecs of the pole, but I don't trust it too much due to possible orthogonality issues (or cone error) with the C8 edge.  Not sure if that's the same thing.

  Anyway tonight, I was hoping to check my current polar alignment with the Quick Star Drift Method, but I'm a little confused as to which calibration star to pick (for the AZ adjust part).  I was planning on using Alpheratz for the first star near the Zenith, when it is on the West side of the Meridian.  But when I push the scope South, towards the second 'calibration star,' I'm having trouble visualizing which star to pick.  Do I pick a star that has the same RA coordinates as Alpheratz?  Also, when moving the scope to the second star in the South, does it matter if I manually push the scope there or can the keypad be used to slew it there? 

  Once I get this done, I might try the other "drift alignment - ra correction method" that's mentioned on page 40.  All I'm trying to do now, is get the RAPAS really dialed in. So in the future, I'm hoping I can get polar aligned with just the RAPAS and then jump right into the modeling!  Thanks any sorry for the long email!

      John


Roland Christen
 

The Daytime alignment is not precise enough to use for aligning the RAPAS. Drift alignment is the best way. It takes a bit of time but once it is done, you don't have to do it ever again after aligning your RAPAS.

Rolando



-----Original Message-----
From: John <obee11@...>
To: main@ap-gto.groups.io
Sent: Mon, Dec 21, 2020 3:40 pm
Subject: Re: [ap-gto] Precise polar alignment of the azimuth axis

Aloha All,

  Well, I was able to get the new Mach 2 out for the first time over the weekend.  So far so good!  Still re-learning the ropes.

  I need to make a slight adjustment to the RAPAS, plus I wanted to check my current polar alignment using "Roland's GTO Quick Star Drift Method" (which can also be found in the  Mach 2 User Guide, Appendix C, pg 41 [dated Aug 2020]).  I used Sharpcap's polar align routine on my C8 Edge at F/7 with an ASI 1600 camera which puts the image scale at 0.55 arc/sec per pixel.  Last night (and Sat night) as a test, I was actually able to get 8 min unguided images without any oblong stars!  Sharpcap says I'm within 0.5 arcsecs of the pole, but I don't trust it too much due to possible orthogonality issues (or cone error) with the C8 edge.  Not sure if that's the same thing.

  Anyway tonight, I was hoping to check my current polar alignment with the Quick Star Drift Method, but I'm a little confused as to which calibration star to pick (for the AZ adjust part).  I was planning on using Alpheratz for the first star near the Zenith, when it is on the West side of the Meridian.  But when I push the scope South, towards the second 'calibration star,' I'm having trouble visualizing which star to pick.  Do I pick a star that has the same RA coordinates as Alpheratz?  Also, when moving the scope to the second star in the South, does it matter if I manually push the scope there or can the keypad be used to slew it there? 

  Once I get this done, I might try the other "drift alignment - ra correction method" that's mentioned on page 40.  All I'm trying to do now, is get the RAPAS really dialed in. So in the future, I'm hoping I can get polar aligned with just the RAPAS and then jump right into the modeling!  Thanks any sorry for the long email!

      John

--
Roland Christen
Astro-Physics


John
 

Aloha Roland,

  ok, thanks!  I need to read up on that drift align procedure a couple more times.  I'm going to adjust the RAPAS to what I have now and then double check more polar alignments

  I'm hoping to get to the keypad modeling next and then move on to the apcc modeling (with Thum) in a couple months.

  The Mach 2 seems to be a great mount!  I was a little over whelmed at first.  And I can carry the mount attached to the ats pier at the same time!  As long as I don't trip I should be ok!  :)

      John


Roland Christen
 

You can use an app like Pempro or PHD2 to do basic drift alignment. They are both good at what they do, although PEMPro is really the standard.

Azimuth alignment:
Since I'm always looking for ways to use new ways to get perfect polar alignment, I have come up with a nifty way (for me) to do the azimuth align. Using MaximDL, I turn on the crosshairs and place a star near the meridian at around Dec = 0 on the center of the crosshairs (using the buttons). I walk away for 10 minutes and take another exposure to see which way the star has drifted and how far. In my case the RA direction is Left to Right, so the star will drift up or down in Dec. I ignore any RA drift at this point, but measure how many pixels the star has moved in that time period and the direction. I usually take an image for reference.

I then put the star back on the crosshairs via the keypad buttons but then move it either left or right along the RA line in the direction of +- declination. Using the azimuth adjuster, I move it near to the right edge to see which direction it drifts. If it drifts in the same direction as before, only faster, I know that I need to place the star on the left side of the center via the azimuth adjuster. I let it drift for 10 minutes again and take a second exposure. Using the two drift positions I can draw a line between the two star positions, and where they intersect is where I need to move the star via the azimuth adjuster.

As an example, let's say that the star drifts 10 pixels north when it is centered, and 20 pixels south when it is near the left edge. That means then that the intersection of a straight line will cross the horizontal crosshair line at about 1/3 of the way from center. And that is where I move the star using the azimuth adjusters. I did this recently with my observatory Mach2 mount and nailed the azimuth so accurately in the first try that I got no drift in Dec for over 30 minutes near the meridian.

Altitude alignment:
For the altitude I have another quick method also, which is quite accurate. I pick a star near Dec = 0, near the meridian (within 1/2 hour or so) and center it on the crosshairs. Can even be the same star as above. I press Rcal to nail it as a reference. Then i simply press Flip Scope. The mount will pick up the star on the opposite side, but offset from the center. I don't worry about left-right offset because that's simply the orthogonal error. I note the amount of N-S error, then move the star using the altitude adjuster until it is exactly 1/2 way to the RA centerline. Then I move it to the crosshair center via the buttons and press Rcal. You can then flip the scope back to the 1st side and repeat the process on that side. A couple of iteration will take maybe 5 minutes and you should be able to go to the RA centerline on each side (ignore the left-right offset). All this assumes that your camera chip is set to line up N-S and E-W and not set at an angle.

Rolando



-----Original Message-----
From: John <obee11@...>
To: main@ap-gto.groups.io
Sent: Mon, Dec 21, 2020 5:47 pm
Subject: Re: [ap-gto] Precise polar alignment of the azimuth axis

Aloha Roland,

  ok, thanks!  I need to read up on that drift align procedure a couple more times.  I'm going to adjust the RAPAS to what I have now and then double check more polar alignments

  I'm hoping to get to the keypad modeling next and then move on to the apcc modeling (with Thum) in a couple months.

  The Mach 2 seems to be a great mount!  I was a little over whelmed at first.  And I can carry the mount attached to the ats pier at the same time!  As long as I don't trip I should be ok!  :)
      John

--
Roland Christen
Astro-Physics


Peter Nagy
 

Hi Rolando, 

This almost looks like Quick Star Drift Method for use with a finder scope using Meridian Delay as described in

https://astro-physics.info/tech_support/mounts/keypad/keypad-manual.pdf

See page 26.

I used to use this method before PoleMaster became available and it worked great. This is good for location that does not have good visible view of Polaris. 

Peter 


John
 

Aloha All,

  I will review all of this, thanks! 

  Somehow I missed the info on page 26 of the pdf file.  That pdf file is for keypad ver 4.19.3 and I was looking in the newer Keypad manual ver 5.x.x.x (dated 11 Nov 2020).
The newer manual is a little different.  No worries!!

  I'm using the Sharpcap polar align tool which is probably similar to the others (ie take an image and rotate the ra axis 90 degrees, take another image, and then adjust the mount to the ncp).
I can do this thru either the guide scope camera on the main C8 camera. But I'm a little worried that I might be introducing some small ortho or cone errors. I guess a Polemaster camera mounted
on front of the Mach 2 would take care of that!  And the modeling will help to (just haven't got to it yet)

    John

 


Steven Panish
 

Look into ConeSharp.  Works REALLY well to eliminate cone error.  From the SharpCap folks.

Steve

On Tue, Dec 22, 2020 at 5:44 PM John <obee11@...> wrote:
Aloha All,

  I will review all of this, thanks! 

  Somehow I missed the info on page 26 of the pdf file.  That pdf file is for keypad ver 4.19.3 and I was looking in the newer Keypad manual ver 5.x.x.x (dated 11 Nov 2020).
The newer manual is a little different.  No worries!!

  I'm using the Sharpcap polar align tool which is probably similar to the others (ie take an image and rotate the ra axis 90 degrees, take another image, and then adjust the mount to the ncp).
I can do this thru either the guide scope camera on the main C8 camera. But I'm a little worried that I might be introducing some small ortho or cone errors. I guess a Polemaster camera mounted
on front of the Mach 2 would take care of that!  And the modeling will help to (just haven't got to it yet)

    John

 


John
 

Aloha Steve,

  Thanks, I will look into that!

  Spent all day (about 7 hrs) looking at drift alignment theory and trying to get my bearings.  I understand it better now.

  Seems like the drift align will be a lot easier sitting down with a camera (then doing it with a cross-hair eyepiece). May start off with PHD2 first
and then try the drift align (first with the star on the meridian/equator followed by the second star close to the horizon.  Then check what the RAPAS is showing.


Steven Panish
 

John,
You might also try the SharpCap polar alignment.  It is simple to do (uses the imaging train) and very accurate as far as I can tell.  I prefer it to drift.

Steve

On Wed, Dec 23, 2020 at 6:40 PM John <obee11@...> wrote:
Aloha Steve,

  Thanks, I will look into that!

  Spent all day (about 7 hrs) looking at drift alignment theory and trying to get my bearings.  I understand it better now.

  Seems like the drift align will be a lot easier sitting down with a camera (then doing it with a cross-hair eyepiece). May start off with PHD2 first
and then try the drift align (first with the star on the meridian/equator followed by the second star close to the horizon.  Then check what the RAPAS is showing.


deonb
 

Steven, I’ve used Sharpcap in the past and have done so with the Mach2GTO as well but I’ve recently discovered that my Sharpcap and Polemaster alignment disagrees with each other by over 4 minutes.

I trust the polemaster more since with that I can do 10 minute unguided at 2800mm with Polemaster alignment and about 2 minutes with Sharpcap alignment.

Obviously I need to look into ConeSharp as a result - just saying the SharpCap method of doing polar alignment shouldn’t be trusted blindly.


John
 

Aloha Steven and Deonb,

  Yes, I have been using the Sharpcap polar align tool and really like it.  And I understand what all is going on now with the az and alt (ie 2 star)
drift alignment.  I'm going to try the PHD2 drift align next and then try another drift align with just a camera (no other software).  And then compare
these various techniques (as what Deonb is doing)...

  I'm kind of curious to see how PHD2 and SharpCap compare (as to what each one is reporting in the way of polar align error).  And then try Roland's method.
I'm sure either method is fine, especially if a little modeling is thrown in afterwards.  Just curious at trying a few different techniques more than anything else.  And I
still need to look into that SharpCap cone error business!

  I was able to get 8 mins unguided exposures the other night in the Pleiades region and ran out of time to try 10 mins.  I did get 10 mins on either Deneb or Sadr,
(on a different night) but you could tell some oblong stars were creeping in to the mix.  One 12 min exposure showed definite oblong stars.  But all without modeling!

    John


Steven Panish
 

10 min. unguided at 2800mm FL is pretty darn good!  Before I used SharpCap's method, I tried various manual drift techniques and only occasionally got it that good.  (C11??)  Now I understand that refraction at different altitudes is an issue - perhaps that was why the PA was never sufficiently reliable for longer unguided exposures.  Additionally my permanent pier is 10" iron pipe and quite tall, so thermally induced dimensional changes are likely an issue.

But although I have not done a new PA since using ConeSharp a few months ago, I earlier found all the procedures to give different results.  Not 4 minutes though.  That's pretty big.  Even when using the SharpCap procedure, redoing it after the 90deg rotation yields a difference  of typically 1minute.  So I split the difference of the two positions and am off about .5min on both.  It is a very quick method, which makes me prefer it over drift. 

Periodically I run the PHD2 guiding assistant, which gives a measure of PA.  It seems very sensitive to sky location, and also varies widely over time, not necessarily settling reliably.  Odd.  After letting it chug along for about 15 minutes it told me the error was 2'.  Sigh.  And with the drift techniques, including semi-automated ones such as in PemPro and PHD2, I found too much interaction when alternating between the Alt and Az settings.  I'd get it perfect on one, do the other, and going back to the first it would be off and/or would never improve with iterations.  That might be better now that the orthogonality is much better.  

At any rate, I gave up on unguided, it's too difficult for a relative newbie like me running at C11 and C9.25 focal lengths.  And I'm doing a lot of 20 min exposures on Sh2 objects.  PHD2 Guiding makes it easy, so I'm just sticking with that until there is some reason not to.  Now my gripe is that I can't get rid of the field curvature with the reducer/correctors.  Well, it's all a learning experience!

Steve

On Sun, Dec 27, 2020 at 1:07 PM John <obee11@...> wrote:
Aloha Steven and Deonb,

  Yes, I have been using the Sharpcap polar align tool and really like it.  And I understand what all is going on now with the az and alt (ie 2 star)
drift alignment.  I'm going to try the PHD2 drift align next and then try another drift align with just a camera (no other software).  And then compare
these various techniques (as what Deonb is doing)...

  I'm kind of curious to see how PHD2 and SharpCap compare (as to what each one is reporting in the way of polar align error).  And then try Roland's method.
I'm sure either method is fine, especially if a little modeling is thrown in afterwards.  Just curious at trying a few different techniques more than anything else.  And I
still need to look into that SharpCap cone error business!

  I was able to get 8 mins unguided exposures the other night in the Pleiades region and ran out of time to try 10 mins.  I did get 10 mins on either Deneb or Sadr,
(on a different night) but you could tell some oblong stars were creeping in to the mix.  One 12 min exposure showed definite oblong stars.  But all without modeling!

    John


Greg McCall
 

Hi,
Re Sharpcap and Polesmaster.
Try the Sharpcap polar align app using the Polemaster camera. 
That works for me and allows setups using Sharpcap without a guide camera.

Greg


Ray Gralak
 

Try the Sharpcap polar align app using the Polemaster camera.
That works for me and allows setups using Sharpcap without a guide camera.
Using the Polemaster camera is the best way to do it.

If a guide camera is used and the entire scope is rotated, there is going to be flexure somewhere, which can affect the calculated polar alignment position.

There is only so much accuracy you are going to get with this method with a guide scope.

-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 Greg McCall
Sent: Tuesday, December 29, 2020 1:53 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Precise polar alignment of the azimuth axis

Hi,
Re Sharpcap and Polesmaster.
Try the Sharpcap polar align app using the Polemaster camera.
That works for me and allows setups using Sharpcap without a guide camera.

Greg


Eric Dreher
 

My image scale is 1.09"/px.  SharpCap works perfectly with my 1600 and 102mm refractor.  Since I use an OAG, I have no guide scope.

One of these nights I plan on doing several PAs with both SharpCap and my Polemaster, using SharpCap and the PM software.  But as rare as clear nights are in my area, I'll only do this when conditions are really bad.


Steven Panish
 

Ray, that is an excellent point.  I use the SharpCap method through the main camera and there is certainly some flexure after the 90 deg rotation in the procedure.  But at any rate, since I'm guiding (through an OAG) the PA is accurate enough, whatever it is exactly.

Steve

On Tue, Dec 29, 2020 at 5:27 PM Ray Gralak <groups3@...> wrote:
> Try the Sharpcap polar align app using the Polemaster camera.
> That works for me and allows setups using Sharpcap without a guide camera.

Using the Polemaster camera is the best way to do it.

If a guide camera is used and the entire scope is rotated, there is going to be flexure somewhere, which can affect the calculated polar alignment position.

There is only so much accuracy you are going to get with this method with a guide scope.

-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 Greg McCall
> Sent: Tuesday, December 29, 2020 1:53 PM
> To: main@ap-gto.groups.io
> Subject: Re: [ap-gto] Precise polar alignment of the azimuth axis
>
> Hi,
> Re Sharpcap and Polesmaster.
> Try the Sharpcap polar align app using the Polemaster camera.
> That works for me and allows setups using Sharpcap without a guide camera.
>
> Greg
>







Cheng-Yang Tan
 

Actually there is a way to see whether your guide scope is flexing w.r.t. the mount with SharpCap (SC):

Do the PA routine in SC as usual with the scope starting at Park 3. Adjust Alt and Az to get your PA to good or excellent. At this point, your scope should be about 90 deg from Park 3. Then in SC hit the restart button. This time, let SC plate solve with the scope at 90 deg from Park 3. Then once SC is done, send the scope back to Park 3. And without touching Alt or Az,  note what what SC reports. It should still be good or excellent to show that flexure is not a problem.

The above routine is described in SC doc:





I use it all the time to make sure that nothing has moved during PA.

IMO, using the guide scope gives a more accurate PA because of its finer image scale. In my workflow, I do a rough PA with PoleMaster (PM) and the PM scope  and then use SC with the guide scope for the final PA. 

Also SC tells you what your PA error is while PM just asks you to eye ball the alignment between the dot in the square and the circle. I think having a PA error allows you to know how precise your PA is.

cytan

P.S. I've never had any success with drift align with PHD2. I think I'm just not patient enough to wait for drift to get the error to a steady value.



On Tuesday, December 29, 2020, 04:27:13 PM CST, Ray Gralak <groups3@...> wrote:


> Try the Sharpcap polar align app using the Polemaster camera.
> That works for me and allows setups using Sharpcap without a guide camera.

Using the Polemaster camera is the best way to do it.

If a guide camera is used and the entire scope is rotated, there is going to be flexure somewhere, which can affect the calculated polar alignment position.

There is only so much accuracy you are going to get with this method with a guide scope.

-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 Greg McCall
> Sent: Tuesday, December 29, 2020 1:53 PM
> To: main@ap-gto.groups.io
> Subject: Re: [ap-gto] Precise polar alignment of the azimuth axis
>
> Hi,
> Re Sharpcap and Polesmaster.
> Try the Sharpcap polar align app using the Polemaster camera.
> That works for me and allows setups using Sharpcap without a guide camera.
>
> Greg
>






Ray Gralak
 

Do the PA routine in SC as usual with the scope starting at Park 3. Adjust Alt and Az to get your PA to good or
excellent. At this point, your scope should be about 90 deg from Park 3. Then in SC hit the restart button. This
time, let SC plate solve with the scope at 90 deg from Park 3. Then once SC is done, send the scope back to Park
3. And without touching Alt or Az, note what what SC reports. It should still be good or excellent to show that
flexure is not a problem.
Because of gravity, there is always flexure. It's just a matter of how much.

The bigger the instrument the more flexure there will be. "Piggy-backed" guide scopes, even if they are light, can be subject to flexure exerted on the rings by the primary scope.

-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 Cheng-Yang Tan via groups.io
Sent: Tuesday, December 29, 2020 4:11 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Precise polar alignment of the azimuth axis

Actually there is a way to see whether your guide scope is flexing w.r.t. the mount with SharpCap (SC):

Do the PA routine in SC as usual with the scope starting at Park 3. Adjust Alt and Az to get your PA to good or
excellent. At this point, your scope should be about 90 deg from Park 3. Then in SC hit the restart button. This
time, let SC plate solve with the scope at 90 deg from Park 3. Then once SC is done, send the scope back to Park
3. And without touching Alt or Az, note what what SC reports. It should still be good or excellent to show that
flexure is not a problem.

The above routine is described in SC doc:

Polar Alignment Troubleshooting – SharpCap – Lunar, Planetary, Solar and Deep Sky Imaging. EAA and Live
Stacking. <https://www.sharpcap.co.uk/sharpcap/features/polar-alignment/polar-alignment-troubleshooting>


<https://www.sharpcap.co.uk/sharpcap/features/polar-alignment/polar-alignment-troubleshooting>

Polar Alignment Troubleshooting – SharpCap – Lunar, Planetary, Solar and...





I use it all the time to make sure that nothing has moved during PA.

IMO, using the guide scope gives a more accurate PA because of its finer image scale. In my workflow, I do a
rough PA with PoleMaster (PM) and the PM scope and then use SC with the guide scope for the final PA.

Also SC tells you what your PA error is while PM just asks you to eye ball the alignment between the dot in the
square and the circle. I think having a PA error allows you to know how precise your PA is.

cytan

P.S. I've never had any success with drift align with PHD2. I think I'm just not patient enough to wait for drift to get
the error to a steady value.



On Tuesday, December 29, 2020, 04:27:13 PM CST, Ray Gralak <groups3@gralak.com> wrote:


Try the Sharpcap polar align app using the Polemaster camera.
That works for me and allows setups using Sharpcap without a guide camera.
Using the Polemaster camera is the best way to do it.

If a guide camera is used and the entire scope is rotated, there is going to be flexure somewhere, which can affect
the calculated polar alignment position.

There is only so much accuracy you are going to get with this method with a guide scope.

-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 Greg McCall
Sent: Tuesday, December 29, 2020 1:53 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Precise polar alignment of the azimuth axis

Hi,
Re Sharpcap and Polesmaster.
Try the Sharpcap polar align app using the Polemaster camera.
That works for me and allows setups using Sharpcap without a guide camera.

Greg






Mike Dodd
 

Because of gravity, there is always flexure. It's just a matter of
how much.

"Piggy-backed" guide scopes, even if they are light, can be subject
to flexure exerted on the rings by the primary scope.
or, if the primary scope rings are lined with felt or other soft material, the primary scope ITSELF could be moving relative to the guide scope.

I replaced the felt in my 130mm APO rings with solid styrene, as seen here: <http://astronomy.mdodd.com/flexure.html#RingLiner>

That page shows seven things I did to vanquish flexure in my system. You can never pay too much attention to tracking down flexure!

--- Mike
http:// astronomy.mdodd.com