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Polemaster and a tree near Polaris ... what to do?

Equipment Imaging Mount Polar Alignment
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#1 jeffcrilly2

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Posted 01 March 2021 - 02:56 PM

Recently (past couple months) I have started to use the Polemaster (as opposed to drift aligning).

 

Once I got the Polemaster dialed in , and my brain wrapped around the necessary workflow, I've found Polemaster to do a fantastic job of aligning the mount , which is on a portable pier on a patio that unfortunately has some shift due to clay soil which tends to heave and move when wet , which means I need to double check polar alignment every night.

Also... my neighbor has a fairly large elm tree which is directly north of the mount location.   However Polaris is usually "just above" the tree so polar alignment is indeed possible.

A couple nights ago I noticed the Polemaster was having a hard time with the "precise pole" step.

 

After closer observation it seems to be using Delta Ursae Minoris for the "precise pole" alignment.

 

Unfortunately this star is kinda buried in the tree.   (see attached images.)

Question:  Is it possible to configure Polemaster to use one of the other stars for "precise pole" alignment?
Any other suggestions?

Thx in advance.

-Jeff

 

I've attached a couple images showing the issue.

Btw.. in case you are wondering...
 

- The tree is not mine, so I can't easily just trim it... however I am considering paying the neighbor to have it trimmed (we're on pretty good terms), but it won't be cheap.

- Moving the mount is not quite an option... there are trees to the south also!    If this is problematic I'll actually probably move the mount further north a bit, and drift align.

- Pulling up stakes and moving to a completely different location is the most preferable option but probably won't happen soon.

Attached Thumbnails

  • polemaster-tree-issue-star-locations.jpg
  • polemaster-tree-issue.jpg


#2 Jim Waters

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Posted 01 March 2021 - 03:04 PM

"Is it possible to configure PoleMaster to use one of the other stars for "precise pole" alignment?NO.  Look into using SharpCap polar alignment.  It use plate solving.

 

https://www.youtube....h?v=ivlgbgNIeTU

 

Other options

  • A chainsaw will solve your problems.
  • Move the mount to another location.
  • Drift alignment.

Edited by Jim Waters, 01 March 2021 - 03:06 PM.

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#3 AgilityGuy

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Posted 01 March 2021 - 03:09 PM

Good post.  You've provided some good information.  I image from several places in my yard and one of the sites has exactly the same problem - I polar align through the center of a large oak tree.  It looks like fairly easy fix.  You've already got enough open space to see you've got the proper rotational axis all you need to do is remove a branch or two that obscures the fine adjustment on Polaris.  Admittedly, scale being everything it may be a six inch diameter branch!  In my case I'm able to align the rotational center with several stars somewhat obscured then I site directly through an open spot in the tree for the fine adjustment.  I was able to open a small workable  window in my tree with a pole saw very easily.  Take a branch at a time and see how it works.  If that isn't feasible, you've got a great start visually to then fine tune with drift alignment.


Edited by AgilityGuy, 01 March 2021 - 03:24 PM.


#4 rgsalinger

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Posted 01 March 2021 - 03:59 PM

I suggest simply raising your tripod or putting in some kind of sturdy platform on which to set the mount. Sharpcap is all well and good but learning a whole new application seems a bit rich when you just need a few inches (?) of additional height.

Rgrds-Ross



#5 pyrasanth

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Posted 01 March 2021 - 04:02 PM

The Ioptron mounts deal with this issue by using a technique called iterative polar alignment where 2 stars are used to fine tune the polar position. I don't know if your mount firware has a similar option.



#6 PFitzhorn

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Posted 01 March 2021 - 04:10 PM

I've used a QHYCCD Polemaster for a couple of years with great success through the top part of a cottonwood tree smack in the middle of my neighbor's yard.  My views are similar to yours.  I'm currently using software version 20.6.28.

 

The "precise pole" step asks one to align the green square with the red circle (actual and computed pole).  Since you've gotten to that point by clicking on Polaris a couple of times, and a visible guide star as well, there shouldn't be an issue. If I've mistaken your problem and you cannot double click on Polaris itself, then I don't see how the Polemaster will be useful. I use the same process that's shown in this video:

 

https://www.youtube....h?v=WT0JHa3WrQw


Edited by PFitzhorn, 01 March 2021 - 04:11 PM.


#7 jeffcrilly2

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Posted 01 March 2021 - 06:07 PM

At one point on Saturday night Polaris was also blocked by a branch -- I wasn't able to see it at all.    
(Alignment was still pretty good from the night before tho as I was able to do 10-20 minute unguided exposures.)

The branches on this tree are rather thin (3 inches?) so I think it doesn't take too long for the stars earth to move showing the stars again... but the tree is now starting to get leafy.

 

I suspect in the summer when Delta Ursae Minoris is higher in the sky in early evening (when polar aligning) it will be less of a problem.

> "all you need to do is remove a branch or two"

Unfortunately it is a neighbor tree... and the branches are fairly high up -- I'm guessing about 30 feet.  
The mount is located approximately 100 feet from the base of the tree.
Cutting some branches is definitely a consideration (for multiple reasons), but it will require getting permission and hiring a tree trimming service with a bucket... we had it done before (different part of the tree unfortunately) for $500.

I thought about raising the mount -- but it is an AP1200 on a 56" pier... so pretty tall already (and heavy).   I could also move it to another location... but the current spot on the property is "optimal" given other trees around the property to the SE and SW.    I have about a 75 degree clear sky straight south and can image above a tall redwood to the SE -- if I move further from north to raise Polaris I will be closer to the redwood and I won't get the sky above the redwood anymore.

I could go back to drift alignment ... it just seems polemaster is faster and quite accurate -- I dunno which is better for sure (I've not objectively done a comparison)... tho I would expect drift aligning... but it takes time.

Thx for the pointer to SharpCap.  It seems I might be able to use SharpCap with the PoleMaster -- I really like the idea of a "camera in the axis of the mount".
I'll need to research SharpCap a bit more.
 



#8 PFitzhorn

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Posted 01 March 2021 - 06:46 PM

Again, from what I see on your pictures, Polemaster should work just fine. My tree view isn't quite that bad, but it's not far off.   You only need Polaris and just one of the five or so other stars in the guide circles to do the alignment, which your photo 1 shows. You can use any one of the other stars that are visible in the small circles, like the one to the left of Polaris.  You don't need the one that isn't visible.

 

Your second photo shows the point where you need to move your alt-az bolts to align the green square (where your mount currently is pointing) over the red circle (where the pole actually is). For that step you don't need any stars and it's immaterial that you cannot see one or two of them. In fact, at that point you don't even need to see the sky since the Polemaster software has figured out where your mount pole is pointing with respect to the actual pole and is simulating both in the software display.

 

Can you describe why you think you should use Delta Ursae Minoris?  In my experience with the Polemaster, I've never used that particular star. BTW, for me now, I polar align about once a month or so, at twilight, and it takes about 5 minutes or less. Man do  I love it.

Regards


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#9 1DegreeN

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Posted 01 March 2021 - 09:27 PM

Definitely worth trying Sharpcap. It will work with the PM as the camera and doesn't need Polaris to be visible. However, looking at the photos you posted of your northern horizon, once those trees are in leaf then even Sharpcap may struggle. A solution may be to use your guide scope + guide camera with Sharpcap instead of the polemaster. This gives a much smaller field of view of course but if the clear area above the tree tops is within 5 to 7 degrees of the NCP you should still be able to complete the polar alignment procedure: e.g with the mount rotated east  to near horizonal, move  a little in declination to raise the scope to point just above the trees; the procedure then asks you to rotate the scope west by around 90 degrees - you have to hope that the scope is then still pointing at an area of clear sky. It may take some practice to find the best spot to begin the procedure and how far to rotate. My northern horizon is also blocked by trees and I used Sharpcap PA in this way for a couple of years until the trees got too tall. 



#10 dgpilot

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Posted 01 March 2021 - 10:11 PM

Everyone has different methods which work great. In my experience drift alignment has worked best and quite easy to do. Before doing it I was always afraid of trying it.. but the PHD tutorial makes it quite easy. 

https://openphdguidi...t_Alignment.pdf



#11 jeffcrilly2

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Posted 02 March 2021 - 02:04 PM

 

Can you describe why you think you should use Delta Ursae Minoris?  In my experience with the Polemaster, I've never used that particular star. BTW, for me now, I polar align about once a month or so, at twilight, and it takes about 5 minutes or less. Man do  I love it.

 

Yes.. I am indeed assuming Polemaster is using Delta Ursae Minoris for the "precise alignment" step.  I have not verified this assumption.  
Also.. as far as I can tell , we Polemaster users don't "use that particular star"... it seems to be automatically selected by Polemaster during the "precise alignment" step.

Here's why I think Polemaster is using Delta Ursae Minoris:  

 

Earlier in the winter when the tree had less leaves (and Delta Ursae Minoris was in a different part of the tree at twilight), the "precise alignment" step was totally doable.  

The "precise alignment" box would jump around a bit due to seeing , but really not problem, and alignment was fast and spot on.

 

With Delta Ursae Minoris now hidden by leaves and branches, the "precise alignment" box is jumping all over the place... like bad seeing... but way worse ...
In the second image attached above :  on the "magnified circle" note how far off the "box" is from the circle.. usually when I get to this step the "precise alignment" is almost touching the circle.
 

It almost looks like the polemaster software is confused: at one point I went ahead and adjusted for the "precise alignment" box but it was obviously way off , like more than a degree from the "rough pole".

After looking at the "precise alignment" screen, it appears to me Polemaster is using Delta Ursae Minoris as there is a "tracking box" over that star.
(In the second image I have an arrow pointing to a box...  this is afaik Delta Ursae Minoris.)

If not tracking the position of Delta Ursae Minoris in the image, what is the purpose of the box?

Also... On another subsequent night, Delta Ursae Minoris was more visible (not blotted out by leaves and/or a branch) and the "precise alignment box" was back to normal (jumping around due to seeing) but totally usable.

 

Three additional things to note for clarification...
1) The QHY manual notes there should be three stars (in the north) visible.    It does not state which stars, but from looking at the charts it seem one of these is Delta Ursae Minoris.
2) I'm pretty sure the star down in the tree (I highlighted with the arrow) is Delta Ursae Minoris... I checked this on the charts, and it seems to match up... but I could be wrong.

3) I've not found anything in the manual allowing me to select another star during the "precise alignment" step; I also didn't find a way to do this in the software.  Tho it would be nice if I could as the other stars are visible.   Perhaps there is a good reason for not using any other stars for the "precise alignment" step, tho I would expect using a star higher in the sky would be better as there is less atmospheric refraction, tho my understanding is polemaster can correct for atmospheric refraction.
 

In six months this won't be a problem as Delta Ursae Minoris will be above the tree.

 

thx 

-jeff

Ps.  I suppose I should also ask on the QHY support site.



#12 PFitzhorn

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Posted 03 March 2021 - 11:25 PM

Yep - polar aligned my Losmandy G11 this evening at twilight and saw exactly what you're talking about in the precise alignment part.  Delta Ursae Minoris is well in the cottonwood tree for me at this phase but it must be just visible enough that the Polemaster software sees it and highlights it, as shown in your 2nd photo in your first post.  I've never paid much attention since it always seems to find it and I've been working on fine tuning  my mount at that part. Sorry I threw you off track in the previous posts.  If you figure this out, please post back here - I suspect that as that cottonwood grows I might be right where you are in a couple of years.


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#13 jeffcrilly2

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Posted 04 March 2021 - 05:48 AM

Yep.. no problem... good discussion.. helped me think this through a bit.   I'll have to check with the QHY site.   

 

Thx for confirming you are seeing the same!



#14 lucam

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Posted 04 March 2021 - 06:44 AM

As other posters suggested, SharpCap with your PoleMaster or even your main OTA camera, unless your field of view is too narrow, should be able to handle those trees. SharpCap platesolves the image using all available stars, so if one is partially hidden behind the branches, it doesn't really affect the result. As far as accuracy goes, SharpCap is at least as good as the PoleMaster software.



#15 avarakin

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Posted 04 March 2021 - 11:33 PM

Latest version of Kstars supports alignment without pointing to pole. You will have to use your guiding or main scope for capturing the alignment images.



#16 jeffcrilly2

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Posted 05 March 2021 - 06:01 AM

> Latest version of Kstars supports alignment without pointing to pole. You will have to use your guiding or main scope for capturing the alignment images.

 

I'll keep that in mind.    Presumably Kstars does drift alignment.   At the moment I've moved to unguided imaging (sans guidescope), tho I could use the main camera for drift alignment.

 

thx



#17 jeffcrilly2

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Posted 05 March 2021 - 06:08 AM

Thx for the reminder about SharpCap.  (I forgot all about it!)  

 

SharpCap looks very promising.   Screenshot below.

 

Unfortunately, I cannot run through the full polar alignment routine at the moment (mount is parked for the night and taking darks; It looks like SharpCap wants to rotate the RA 90 degrees and so on.)
The weather is calling for rain / clouds for a few days... I'll pick this up next week.

thx

 

-jeff

 

 

Attached Thumbnails

  • SharpCap+PoleMaster+Tree.jpg


#18 avarakin

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Posted 05 March 2021 - 10:59 PM

> Latest version of Kstars supports alignment without pointing to pole. You will have to use your guiding or main scope for capturing the alignment images.

 

I'll keep that in mind.    Presumably Kstars does drift alignment.   At the moment I've moved to unguided imaging (sans guidescope), tho I could use the main camera for drift alignment.

 

thx

Drift alignment is legacy in Kstars. The current method is using plate solving. 



#19 jeffcrilly2

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Posted 12 March 2021 - 05:06 AM

I just wanted to update this thread with my finding on PolarAlignment with SharpCap and the PoleMaster camera ... It Just Works.   
In fact it is seemingly faster than the PoleMaster algorithm.

 

SharpCap is also able to plate solve stars in between leaves and branches in the tree.

 

Definitely worth $15 for the unlocked SharpCap.

 

Btw.. I did poke around in kstars, but TBH I could not figure out the polar alignment tool there.   I might not have looked long enough tho.

 

Thx all.

 

-jeff




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