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Old 29-11-2020, 02:32 PM
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OneCosmos (Chris)
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Am I really PolarAligned?

I have PoleAlignMaster from QHY and I have found it extremely easy to follow the specified routine perfectly so in theory I'm perfectly polar aligned, but I don't really know because I don't see that PoleMaster tells you how good your alignment really is.


Once I finished the routine therefore I saved the view the camera sees and took it in to SG Pro to platesolve, expecting to see numbers that were very close to the pole. What I actually got surprised me:


RA 18:44:33
DEC -88 59 22
Angle 122.26
Scale 24.69
Confidence: 100


Now that suggests that on the surface, i'm close but still not very close in DEC and way off in RA, but how can that be? Everyone raves about PoleAlignMax and so long as you follow the steps carefully you should be pretty accurately polar aligned at the end of it.


Am I right in thinking the DEC should indeed be saying 90 and RA should be?? 0? 24? - Anyway, anything surely but 18? Remember the camera isn't in the telescope it is attached to the polar axis so should really be viewing dead on the pole? Am I missing something or is PoleAlignMaster simply not all that accurate?


Chris
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Old 29-11-2020, 03:15 PM
glend (Glen)
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Can you get it to display Alt and Az? Which should be simply your latitude and 180 degrees.

It maybe working off the RA and Dec for one of the stars of near the SCP, like Sigma Octanis.

Regardless of what that tool tells you, you may need to add calibration stars to your mount alignment. If you slew to target stars either side of the Meridian, near the equator, are they dead centre in the field of your chosen scope? Then you have possible scope cone error as well.

Last edited by glend; 29-11-2020 at 03:26 PM.
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Old 29-11-2020, 05:13 PM
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Hi Chris,
put a camera in your focuser.
Point the telescope at about 45 degrees altitude facing North.
Start taking an exposure while pressing the West button X1 speed on you hand control for 40 seconds.
Then Press East X1 speed for 40 seconds.
Then stop.
Finish the exposure.
Check that you have a straight line back and forth on the camera picture.
If you have a V shaped line you're not polar aligned.
Adjust the mount rotation screws left or right and repeat until

you get a straight line.



cheers
Allan
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Old 29-11-2020, 05:40 PM
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OneCosmos (Chris)
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Quote:
Originally Posted by glend View Post
Can you get it to display Alt and Az? Which should be simply your latitude and 180 degrees.

It maybe working off the RA and Dec for one of the stars of near the SCP, like Sigma Octanis.

Regardless of what that tool tells you, you may need to add calibration stars to your mount alignment. If you slew to target stars either side of the Meridian, near the equator, are they dead centre in the field of your chosen scope? Then you have possible scope cone error as well.
Well, it is very new and Ive only used it once as a test but when I did a GoTo to M42 yes it smack in the middle of the EP but were not talking high magnification - Ethos 13mm in a 450mm scope for 34x, but still, in the middle.
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Old 29-11-2020, 10:11 PM
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OneCosmos (Chris)
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Perhaps someone also using polemaster can do as I did and platesolve the view from the camera after running the routine and let me know the numbers they get?
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Old 30-11-2020, 01:59 AM
Zuts
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Quote:
Originally Posted by OneCosmos View Post
Perhaps someone also using polemaster can do as I did and platesolve the view from the camera after running the routine and let me know the numbers they get?
I am not an expert but as Glen said. The camera is on the mount and the scope is not 100% aligned with the polemaster camera. So when you plate solve from an image from the scope how do you know it is exactly pointing where the polemaster is pointing.

In any case, given your comment about M42, it works , and is good enough for viewing and imaging.
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Old 30-11-2020, 07:44 AM
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The step in the Polemaster routine where you pick a star, rotate, pick it again, then rotate and pick it again is for the software to work out where the center of rotation is in the images produced by the Polemaster. That is the aim point of the RA axis of the mount and the point that you are trying to line up with the pole but it may not necessarily be the center of the Polemaster field of view, which is why you need to go through the steps to determine it. I am assuming here that the camera view you were plate solving was the Polemaster? If it was the view through the main scope then you have probably got even more errors to contend with.

What that means is that you can't just plate solve the Polemaster image and trust that as being your error form the pole. If you plate solve one with the scope to the west and counterweight bar horizontal, then plate solve another with the scope to the east and counterweight bar level, half the difference in Dec reading would be your error, but it is likely to be so small an error that it probably is not a great way to check it. You would be better off with a drift align check in PHD2 or the DARV check that Allan described.
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