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Looking for beta testers of new Polar Alignment utility.


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5 hours ago, themos said:

PPA measures the Polar Alignment error in angular displacement in Azimuth and Altitude. It does not require a Goto mount or a LiveView capable camera (because I wanted it to be useful even with basic quipment, like barn tracker mounts and compact cameras).

These error numbers are exactly what  PoleFocus requires to help you correct the error (by adjusting the direction your Polar Axis is pointing). It requires Goto capability and LiveView.

So each bit of software does a different job. AstroTortilla also calculates the Polar Alignment Error but people have had mixed results with it (AT uses GoTo) and development of AT seems to have stopped.

I can't say that they are throwing away 300Euros. I can say that PPA, for me (and a few others) works just fine. The extra hassle is that I have to mount my DSLR with a 135mm lens, piggy-back on the scope, for polar alignment and then take it back to prime focus of the telescope, but it's not a deal-breaker! And I need to carry enough plate-solving software on the laptop, but again it's not too bad. 

thank you for taking the time to clarify this :)  I'll look into your software as it looks really good from what I gather reading this thread.

Nice to see that there are still people trying to improve on this process as it can be confusing to the newcomers. I still see on a regular basis people starting threads on PA and confusing 3 stars alignment with polar alignment. In my case, it has always been the issue of what to do when polaris is not visible... learning an alternate method has saved my night a couple of time ;)

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Hello, if you would like to volunteer to try out a new Polar Alignment method, please let me know. The requirements are: You can see the Polaris/NCP region from where you usually set up. (S

Sounds good.  Unfortunately at the moment it looks as though I will be unable to help for a while.  Unless it's possible to polar align without being able to see any stars whatsoever.  For weeks Jame

YES!!! Now that I have the camera oriented as described above the "move" instructions make sense and I now have a polar alignment error of 0.54 arc min. I then started all over again, deleted my image

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15 hours ago, Vox45 said:

I still see on a regular basis people starting threads on PA and confusing 3 stars alignment with polar alignment.

one-star, two-star, 3-star procedures should always be called Syncs, not alignments.

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  • 2 weeks later...

I haven't had a chance to read this entire thread yet, but it sounds fascinating.  If you still need beta testers, please let me know. I am an experienced developer and astrophotographer.

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question The distannce to the NCP differents year by  year, Even the polemaster is not corrected on this i understood new update of the software must correct this. How is this corrected in this program and is it in 5 a 10 years still correct. Can some explain how this is working

 

Chris

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Hoi  themos

I like to have option that the popup with the picture is disabled after clicking "Find Polar Axis" or "show improvement" but the calculation is still done i think the change of values are the most inportant of you program. Although the pictures makes the program complete and visable what is going on.

Any posibility in the settings screen for this?  and if possible  the before and after values,  i lke to have  in the screen  ;-) Sorry 

Iam a newbie in python i am not yet able to do it my self.

Chris

 

 

 

 

Edited by calberts
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6 hours ago, calberts said:

Hoi  themos

I like to have option that the popup with the picture is disabled after clicking "Find Polar Axis" or "show improvement" but the calculation is still done i think the change of values are the most inportant of you program. Although the pictures makes the program complete and visable what is going on.

Any posibility in the settings screen for this?  and if possible  the before and after values,  i lke to have  in the screen  ;-) Sorry 

Iam a newbie in python i am not yet able to do it my self.

Chris

 

 

 

 

Open PPA.py in Notepad and find the lines like 

self.create_imgwin

and turn them into comments, like this.

#self.create_imgwin

Then , find the function update_display and add the last line "print inst" so that it lines up with the previous line

    self.wvar9.configure(text=inst)
    print inst

The picture serves as a visual check, by the way. You are supposed to check that there's stars (and the right stars!) in the centre of the circles.

Edited by themos
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On 20 May 2016 at 21:44, themos said:

The bottom line is "don't sweat the small stuff"

Polar axis alignment requirements for astronomical photography

http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1989JBAA...99...19H&db_key=AST&page_ind=0&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES

An interesting article thanks.   Reference 1 also looks like a fascinating read  https://archive.org/details/AmateurAstronomersHandbook

Andy

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18 hours ago, themos said:

Open PPA.py in Notepad and find the lines like 


self.create_imgwin

and turn them into comments, like this.


#self.create_imgwin

Then , find the function update_display and add the last line "print inst" so that it lines up with the previous line


    self.wvar9.configure(text=inst)
    print inst

The picture serves as a visual check, by the way. You are supposed to check that there's stars (and the right stars!) in the centre of the circles.

works partly the windows with the images i modified that with succes.

but te before and after value didn't  work  (print inst)

i had the idea like

                  Find Polaris Value            = Right 00:04:01 UP 00:00:05

                  Improved Polaris Value    = Right 00:00:08 UP 00:00:20

Because the iterations are only based on the horizontal images

I understand you qoute "The picture serves as a visual check, by the way. You are supposed to check that there's stars (and the right stars!) in the centre of the circles."

 

 

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Hello calberts,

I think you would like the new numbers to appear on the GUI window, but below earlier values, is that right? By the way, the numbers (and directions) do not refer to Polaris as such, but to how you should move the mount's polar axis (imagined as a point on the celestial sphere).  

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7 minutes ago, themos said:

Hello calberts,

I think you would like the new numbers to appear on the GUI window, but below earlier values, is that right? By the way, the numbers (and directions) do not refer to Polaris as such, but to how you should move the mount's polar axis (imagined as a point on the celestial sphere).  

Yep thats correct i understood that.

Also question, if  i am correct when you take your V.images and Your H.images the only what differents during the whole session tunning the mount is the i.image

 

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Yes, I take just one vertical image and then, after the first horizontal image, I find the polar axis (left button). All images after that are horizontal and each can be used to show the improvement (right button). At the end, I confirm the alignment with another vertical/horizontal pair.

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6 hours ago, themos said:

 At the end, I confirm the alignment with another vertical/horizontal pair.

Do you actually take 2 images or do you reuse the last horizontal image as it has already been solved?

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I take both a vertical and horizontal at the end, mainly because I like to rotate the mount through large angles to make sure it's settled. I usually do this with light portable mounts, not so much with my EQ6.

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10 hours ago, themos said:

I take both a vertical and horizontal at the end, mainly because I like to rotate the mount through large angles to make sure it's settled. I usually do this with light portable mounts, not so much with my EQ6.

Thanks.

I will be taking my  Astrotrac & pier to Cape Verde later this month so I will try that and see what the outcome is.

I am hoping not to have to drift align the Astrotrac as that generally takes hours :( 

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  • 2 months later...
On 22/08/2016 at 11:27, Fraleo62 said:

I just diacovered this topic and read the original pdf....with the math

I dont understand the need of the initial rotation to the zenith..

Can someone clarify ??

Thx

Franco 

Hello Franco, I am not sure which pdf file you mean. 

Themos

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  • 1 year later...

Hi Guys, 

I'm just trying to use PPA.  Here are my inputs and outputs.

In This photo:

cv25.png.deb023b14b7955e7f60d2bce33b5bdb9.png

What are "5" and "10"? If they are minutes, could they be labelled 5' & 10'?  Is the green cross NCP?  Again, could it be labelled?  I assume the red cross is my actual alignment.  Could it be labelled?  I'm not sure what with, because everything I think of is too long (Like X - actual polar alignment), maybe actually a legend would be better.  Not sure about this.

UPDATE: Ok, I've looked at the code.  They are indeed minutes.  Here is a suggested update at line 640

        # text in arcminutes
        draw.text((ax1 + (rad*26)/36, ay1 + (rad*26/36)), str(i)+"'",
                  font=font)
    # Label ncp
    font = ImageFont.load('helvR10.pil')  # Download helvR10.pil & helvR10.pbm from https://github.com
    draw.text((ax1 + 5, ay1 - 20), "ncp", font=font)
    font = ImageFont.load('helvR24.pil')

Showing this:

cv27.png.2fb820077d60f1366cd18b8c63bfdfe3.png

Then I have this:

cv26.png.d5df338a155b2836bab079e3317b57be.png

Right 00:03:51 Down 00:08:44.  I'd like to know how many turns of the screw is this.  It probably varies with each mount, but it would be nice to know how to put this info into practice rather than trial and error.  I guess I could measure the thread on my screw, calculate what one turn would give me in arc minutes and use that.  Maybe a small table of common threads or common mounts?  Anyway it probably amounts to a very small amount.

Finally, when I calculate it by hand I get 14' deviation.  It's possible that my calculation is wrong, I can post it here later, but either way my polaris is in the tiny circle on my polar scope, and this seems an infeasibly large deviation in comparison.  Maybe my polar scope is not straight, I should look again.  UPDATE: However, it seems to me that Polaris is at 44 min off ncp not 40 min as shown on pic, so not everything is correct

In any case, this is a great product, I'll continue to play with it.

Regards

Steve

DSC_3591.jpg

DSC_3592.jpg

Edited by SteveBz
typo
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Hello,

I've added your ideas in the GitHub Issues. I am not sure when I will find time to add these but they are there in case anyone is tempted to implement them and do a pull request. Polaris was at ~44 minutes in J2000 but not now! PPA does adjust for the wandering of the Earth's axis (precession).

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8 hours ago, themos said:

Hello,

I've added your ideas in the GitHub Issues. I am not sure when I will find time to add these but they are there in case anyone is tempted to implement them and do a pull request. Polaris was at ~44 minutes in J2000 but not now! PPA does adjust for the wandering of the Earth's axis (precession).

OK, well tell me what to do and I'll do it.

I'll check where I got the RA and Dec for Polaris from, I thought it was Stellarium, but anyhow I'll chase it through.  Maybe that's the source of the discrepency in my own calculation (14' vs 9.6' from PPA).  It's about the same magnitude.

Steve

Edited by SteveBz
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2 hours ago, SteveBz said:

I'll check where I got the RA and Dec for Polaris from, I thought it was Stellarium, but anyhow I'll chase it through.  Maybe that's the source of the discrepency in my own calculation (14' vs 9.6' from PPA).  It's about the same magnitude.

I can see that you are correcting using AstroPy, so it should be correct.  However, I looked at Stellarium and it says it's 'Current date'.  RA & Dec (Current date) are (43:78, 89:34).  89:34 is 26' off NCP, so it would seem to be the just past the 20' circle not on the 40' circle.  Have I got that right?

Steve

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I would also like it to operate more remotely.  I don't have a goto scope, so I can't slew at speed, but I can probably slew 30 degs in RA in under ten minutes, which is acceptable.  Would a 30 degree separation in planes be enough to polar align, do you think?  Obviously I still need to go outside to twist the alignment screws.

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