Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

New PHD2 static polar alignment tool

  • Please log in to reply
61 replies to this topic

#1 KenS

KenS

    Apollo

  • *****
  • topic starter
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 27 September 2017 - 05:22 PM

It's been 18 months since I first started working on a tool to polar align from the polar region using a guidescope.

Now it's a tool within PHD2 and available in the latest dev release. Documentation will follow shortly.
Why static alignment? No reason other than to distinguish from the various forms of drift alignment.
This tool lets you polar align by pointing at the pole rather than the equator and in my testing so far is pretty quick. It works particularly well in the Southern Hemisphere due the availability of several identifiable stars near the pole.
Feedback welcome.


  • Iver, DuncanM, Merc and 10 others like this

#2 AndrewXnn

AndrewXnn

    Ranger 4

  • -----
  • Posts: 306
  • Joined: 29 Aug 2015
  • Loc: Mexico, NY

Posted 27 September 2017 - 05:48 PM

Polaris is available for alignment in the Northern Hemisphere.

 

Is there something I'm missing?


Edited by AndrewXnn, 27 September 2017 - 05:48 PM.

  • mr1337 likes this

#3 Goofi

Goofi

    Cosmos

  • *****
  • In Memoriam
  • Posts: 8,137
  • Joined: 03 May 2013
  • Loc: Coastal Southern California

Posted 27 September 2017 - 05:52 PM

Thanks for the update Ken .... now if only I could see Polaris from my location.  Are there any particular specs needed on camera/field of view?


  • isoplut and xiando like this

#4 KenS

KenS

    Apollo

  • *****
  • topic starter
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 28 September 2017 - 02:26 AM

Polaris is one of the stars one can align with. There are 6 coded into the tool (easily added to) and they are all closer to the pole than Polaris. However they are fainter at mag 9 to mag 10. It can work at up to 5 degrees from the pole if extra alignment stars are added. Hopefully some live testing will help identify some. Note that only 1 alignment star is needed. There's no real limit on FOV. I tested with FOV of 36'x24' and it was fine. Larger is generally easier as the alignment stars are easier to find.

In the Southern Hemisphere there are numerous mag 7 and 8 stars less than 30' from the pole.



#5 KenS

KenS

    Apollo

  • *****
  • topic starter
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 28 September 2017 - 03:25 AM

Here's a screen shot of what to expect:
TEST03.png
The window shows the positions of the alignment stars as they should appear in your FOV. The mount rotates on command to select two points and calculates the centre of the arc. The two points are shown on the main display as small blue circles. You can see how small a slew distance is needed to calculate the magenta circle. The red and blue lines show the alt and azimuth adjustments needed to bring the centre of rotation to the pole. The main adjustment needed here was in azimuth (blue).


  • mclewis1, kingjamez, Guest7564635 and 2 others like this

#6 George Simon

George Simon

    Viking 1

  • *****
  • Posts: 708
  • Joined: 01 Jul 2008
  • Loc: Chesnee, SC

Posted 28 September 2017 - 10:42 AM

This tool sounds very interesting and promising. Have you done any testing to quantify how close it brings you to perfect PA?



#7 kingjamez

kingjamez

    Vanguard

  • *****
  • Posts: 2,310
  • Joined: 03 Oct 2006
  • Loc: Fairfax, VA

Posted 28 September 2017 - 10:46 AM

Looking forward to giving this a try! So PHD moves the mount rather than the user (as Sharpcap does)?

 

-Jim



#8 Guest7564635

Guest7564635

    Viking 1

  • ****-
  • Posts: 500
  • Joined: 08 Nov 2013

Posted 28 September 2017 - 12:55 PM

interestingsmirk.gif  Thanks for the update



#9 George Simon

George Simon

    Viking 1

  • *****
  • Posts: 708
  • Joined: 01 Jul 2008
  • Loc: Chesnee, SC

Posted 28 September 2017 - 02:17 PM

Question: Will this tool work if PHD is connected via "On Mount" rather than via ASCOM-enabled software?



#10 KenS

KenS

    Apollo

  • *****
  • topic starter
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 28 September 2017 - 05:36 PM

This tool sounds very interesting and promising. Have you done any testing to quantify how close it brings you to perfect PA?

Only by eyeballing the display. In the southern hemisphere there is a distinctive set of pointer stars pointing to the SCP and only about 2 arcminutes away so checking polar alignment is pretty easy to within an arcminute. I wasn't able to check with a drift alignment due to clouds. Subsequent imaging sessions showed very little drift in dec. One of the aims of beta testing is to establish the accuracy as some settins can be tweaked.

 

Looking forward to giving this a try! So PHD moves the mount rather than the user (as Sharpcap does)?

 

-Jim

In auto mode yes. It works out how far it needs to slew and uses PHD2's guiding ability to track the star as the mount slews. A further benefit is that it only needs two positions as it knows how far it has moved and in what direction.

 

Question: Will this tool work if PHD is connected via "On Mount" rather than via ASCOM-enabled software?

Yes. The tool detects when the mount cannot slew under computer control and enters manual mode. That is much more like SharpCap as you need to move the mount manually and click a button at each of three positions. Since the tool does not know where the mount is pointing all displays assume that you are at the home position. It means you need to place three stars onto their respective "orbits" to align.



#11 kingjamez

kingjamez

    Vanguard

  • *****
  • Posts: 2,310
  • Joined: 03 Oct 2006
  • Loc: Fairfax, VA

Posted 28 September 2017 - 10:11 PM

I gave it a go tonight. I have my mount on a pier and I know that my polar alignment is good.

 

When in the alignment tool, it wants you to click on the star that you choose in the main guiding window. I found that you have to close the tool in order to be able to click on a star. It'd be nice if you didn't have to do that. 

 

From there, the star kept getting lost as soon as the mount started to move. I tried re-clicking on the star after movement, no luck.

 

One time it did work, but the circles where waaaay off screen so something wasn't valid.

 

Not to pile it on (because this can be AWESOME), but I don't really get the "green" and "orange" in the description. It "seems" to me like it's the red and the blue lines that I need to look at, but maybe I'm just not understanding the feedback mechanism.

 

Again, this is going to be great! Thank you for putting it into PHD!

 

-Jim



#12 KenS

KenS

    Apollo

  • *****
  • topic starter
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 30 September 2017 - 04:22 AM

I gave it a go tonight. I have my mount on a pier and I know that my polar alignment is good.

 

When in the alignment tool, it wants you to click on the star that you choose in the main guiding window. I found that you have to close the tool in order to be able to click on a star. It'd be nice if you didn't have to do that. 

 

From there, the star kept getting lost as soon as the mount started to move. I tried re-clicking on the star after movement, no luck.

 

One time it did work, but the circles where waaaay off screen so something wasn't valid.

 

Not to pile it on (because this can be AWESOME), but I don't really get the "green" and "orange" in the description. It "seems" to me like it's the red and the blue lines that I need to look at, but maybe I'm just not understanding the feedback mechanism.

 

Again, this is going to be great! Thank you for putting it into PHD!

 

-Jim

Thanks for the feedback Jim. Which version of Windows are you running? It should be possible to select a star without closing the window so I wonder if it is OS dependent?

If the automatic slew has problems you can try manual mode. If the points it reads have problems that would explain the strange display.

You are right about the green/orange. I changed the code but forgot to change the instructions. That has been corrected and wil be in the next release.

If you get a chance to get a screen shot that would be very helpful as I've no idea how it looks in the northern hemisphere.

The help documentation is in progress right now so hopefully that will help everyone.



#13 kingjamez

kingjamez

    Vanguard

  • *****
  • Posts: 2,310
  • Joined: 03 Oct 2006
  • Loc: Fairfax, VA

Posted 30 September 2017 - 05:39 AM

Thanks again Ken!

 

I gave it a go this morning again and indeed, I messed something up and can now click on a star with the tool window up. That problem happened to me 4-5 times on the previous run, I wonder what I was doing wrong?

 

Unfortunately, when I read this the sun was just coming up and the sky too bright to try to polar align. I'll give it a go again as soon as I can.

 

-Jim



#14 Charlie B

Charlie B

    Surveyor 1

  • -----
  • Posts: 1,504
  • Joined: 22 Mar 2008
  • Loc: Sterling, Virginia

Posted 30 September 2017 - 05:12 PM

Here's a screen shot of what to expect:
attachicon.gifTEST03.png
The window shows the positions of the alignment stars as they should appear in your FOV. The mount rotates on command to select two points and calculates the centre of the arc. The two points are shown on the main display as small blue circles. You can see how small a slew distance is needed to calculate the magenta circle. The red and blue lines show the alt and azimuth adjustments needed to bring the centre of rotation to the pole. The main adjustment needed here was in azimuth (blue).

I gave this a try last night.  My only issue was that I could not scroll the instructions in the window.  My observatory computer is a HP 360 laptop/tablet.

 

Regards,

 

Charlie B



#15 KenS

KenS

    Apollo

  • *****
  • topic starter
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 30 September 2017 - 11:00 PM

 

Here's a screen shot of what to expect:
attachicon.gifTEST03.png
The window shows the positions of the alignment stars as they should appear in your FOV. The mount rotates on command to select two points and calculates the centre of the arc. The two points are shown on the main display as small blue circles. You can see how small a slew distance is needed to calculate the magenta circle. The red and blue lines show the alt and azimuth adjustments needed to bring the centre of rotation to the pole. The main adjustment needed here was in azimuth (blue).

I gave this a try last night.  My only issue was that I could not scroll the instructions in the window.  My observatory computer is a HP 360 laptop/tablet.

 

Regards,

 

Charlie B

 

Thanks Charlie. That should be easy to fix if wxWidgets cooperates. So did you get a reasonable polar alignment?



#16 KenS

KenS

    Apollo

  • *****
  • topic starter
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 30 September 2017 - 11:03 PM

Thanks again Ken!

 

I gave it a go this morning again and indeed, I messed something up and can now click on a star with the tool window up. That problem happened to me 4-5 times on the previous run, I wonder what I was doing wrong?

 

Unfortunately, when I read this the sun was just coming up and the sky too bright to try to polar align. I'll give it a go again as soon as I can.

 

-Jim

I'll see if I can find a way to either minimise the window or make it smaller and easily enlarge it again. I was trying it out with a smaller screen and it does get in the way. Plus if I minimise the window there's no icon to bring it back so I had to minimise the main window then maximise it to bring everything back.



#17 Charlie B

Charlie B

    Surveyor 1

  • -----
  • Posts: 1,504
  • Joined: 22 Mar 2008
  • Loc: Sterling, Virginia

Posted 01 October 2017 - 09:34 AM

 

 

Here's a screen shot of what to expect:
attachicon.gifTEST03.png
The window shows the positions of the alignment stars as they should appear in your FOV. The mount rotates on command to select two points and calculates the centre of the arc. The two points are shown on the main display as small blue circles. You can see how small a slew distance is needed to calculate the magenta circle. The red and blue lines show the alt and azimuth adjustments needed to bring the centre of rotation to the pole. The main adjustment needed here was in azimuth (blue).

I gave this a try last night.  My only issue was that I could not scroll the instructions in the window.  My observatory computer is a HP 360 laptop/tablet.

 

Regards,

 

Charlie B

 

Thanks Charlie. That should be easy to fix if wxWidgets cooperates. So did you get a reasonable polar alignment?

 

Actually, I'm on a pier and had a good alignment.  I wanted to see how the PHD2 static alignment worked.

 

Regards,

 

Charlie B



#18 KenS

KenS

    Apollo

  • *****
  • topic starter
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 01 October 2017 - 07:26 PM

Hopefully it confirmed that your alignment was correct :) 



#19 kingjamez

kingjamez

    Vanguard

  • *****
  • Posts: 2,310
  • Joined: 03 Oct 2006
  • Loc: Fairfax, VA

Posted 01 October 2017 - 07:54 PM

How can I alter how much it moves the mount? I tried again tonight and every time it moves the mount the star gets lost. I tried upping the search box size to 50, don't know if that would help or not, but it didn't. Even so, the star moved outside of the search box every time anyway. 

 

I know I can do it manually, but just providing feedback on the motorized method.

 

-Jim



#20 KenS

KenS

    Apollo

  • *****
  • topic starter
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 01 October 2017 - 08:21 PM

How can I alter how much it moves the mount? I tried again tonight and every time it moves the mount the star gets lost. I tried upping the search box size to 50, don't know if that would help or not, but it didn't. Even so, the star moved outside of the search box every time anyway. 

 

I know I can do it manually, but just providing feedback on the motorized method.

 

-Jim

The tool calculates how much to move based on a hard coded parameter and the search box size. It should stay well within the box at al times. Can you send me the PHD2 Debug log so I can work out why it is moving too far? 



#21 Iver

Iver

    Mariner 2

  • *****
  • Posts: 275
  • Joined: 12 Oct 2007
  • Loc: Monterey County,Ca.

Posted 01 October 2017 - 08:45 PM

              Hi Ken, I tried your app. last night! Everything went well until I attempted to adjust the Alt. and Az. The adjustments didn't move the star along the Red and Blue lines, the Az. Adj. moved the star down the Grey line so that is what I did. I don't think that was what I should have done since I ended up with a lot of Dec. drift. Any Idea what I may have done wrong?

 

Capture 2.JPG



#22 KenS

KenS

    Apollo

  • *****
  • topic starter
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 02 October 2017 - 05:52 AM

              Hi Ken, I tried your app. last night! Everything went well until I attempted to adjust the Alt. and Az. The adjustments didn't move the star along the Red and Blue lines, the Az. Adj. moved the star down the Grey line so that is what I did. I don't think that was what I should have done since I ended up with a lot of Dec. drift. Any Idea what I may have done wrong?

 

Hi Iver, It looks like you did everything right. just looking at the screen shot the first odd thing I notice is the location of the grey cross which is supposed to be at the centre of the sensor. So there may be something going on with the pixel scale and/or camera angle readings

The good news is that it looks like the tool has correctly calculated the centre of rotation. I'm assuming your reference star is Polaris based on its brightness.

 

Can you confirm that the pixel scale and camera angle are correct. That can be done anytime by starting PHD2, connecting to the camera and mount and opening the Static PA tool. The Pixel scale and camera angle are displayed on the screen. Let me know what it says.

What I'd like to check is where Polaris should have been in relation to the pole when you did the alignment. Its possible I've got a directional error in the northern hemisphere calculation. So if you can say roughly what local time you were doing the alignment that will help. 

Or send me the Debug log and I can work it all out.



#23 Iver

Iver

    Mariner 2

  • *****
  • Posts: 275
  • Joined: 12 Oct 2007
  • Loc: Monterey County,Ca.

Posted 03 October 2017 - 12:25 AM

          Ken, it was about 10:00 PM Pacific daylight savings time when I tried your app. I have two 50mm guide scopes I was using the 180mm fl scope but I had the 200mm as the fl in the guide tab. Not sure how the +0.000 camera angle is arrived at?  I think I took the screen shot of the full PHD2 window but it's possible I only captured what I felt was needed.

 

 

 

Capture3.JPG


Edited by Iver, 03 October 2017 - 12:31 AM.


#24 KenS

KenS

    Apollo

  • *****
  • topic starter
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 03 October 2017 - 01:12 AM

          Ken, it was about 10:00 PM Pacific daylight savings time when I tried your app. I have two 50mm guide scopes I was using the 180mm fl scope but I had the 200mm as the fl in the guide tab. Not sure how the +0.000 camera angle is arrived at?  I think I took the screen shot of the full PHD2 window but it's possible I only captured what I felt was needed.

 

 

 

attachicon.gifCapture3.JPG

The dfference in focal length will have a bit of an impact as it is used to work out the pixel scale which in turn affects the drawing of the graphics overlay. It may be enough difference to account for the error in alt/az corrections.

The camera angle comes from the calibration data but requires a mount to be connected to be accessible. An angle of 0 means your sensor X-axis is aligned to East but can also indicate that a mount is not connected.

I'm pushing through a bug fix after I do some testing tonight. It might also addres syour problem but I think the focal length is the main cause.



#25 KenS

KenS

    Apollo

  • *****
  • topic starter
  • Posts: 1,091
  • Joined: 10 Jan 2015
  • Loc: Melbourne, Australia

Posted 03 October 2017 - 06:36 AM

 

How can I alter how much it moves the mount? I tried again tonight and every time it moves the mount the star gets lost. I tried upping the search box size to 50, don't know if that would help or not, but it didn't. Even so, the star moved outside of the search box every time anyway. 

 

I know I can do it manually, but just providing feedback on the motorized method.

 

-Jim

As an afterthought, it could be that the focal length or pixel size entered into PHD2 is incorrect. The clue came from Iver's post earlier. Currently I show the pixel scale on the screen but I suspect that showing the focal length and pixel size could be more intuitive.

Tonight was clear enough for testing so I did a number of tests at different focal lengths, different reference stars and at many distances from the pole inclduing one where it was several FOVs away. I've just submitted a bug fix plus a few useability changes which shoudl become available in the next dev release.


  • George Simon and Merc like this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics