Polar alignment isn't correct even though Sharpap Says excellent

Using SharpCap's Polar Alignment feature
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backyardastrokiwi
Posts: 5
Joined: Sat Apr 18, 2020 12:55 am

Polar alignment isn't correct even though Sharpap Says excellent

Post by backyardastrokiwi »

Polar alignment was out by up to 10 arc minutes even though Sharpcap said it was excellent 3 nights in a row now. I noticed this issue because drift was bad even at 5 minute exposures. After doing a PHD2 drift alignment the issue was fixed, however sharpcap still showed the same results.

One other thing that I noticed was that the SSP was not centered in the image when Sharpcap said it was excellent even though my gear was perfectly aligned, shouldn't it be? It was on the far left lower part of the frame.

I've been using PA routine in Sharpcap for quite some time now and haven't had any issues until recently.

Any help would be much appreciated.
gregm
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Location: Sydney, Australia
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Re: Polar alignment isn't correct even though Sharpap Says excellent

Post by gregm »

I'm curious to know what latitude as that indicates how low the pole is and if you had the atmospheric correction box ticked (just going on memory re the name of the tick box)
I've wondered how the accuracy compares with drift alignment as well as polemaster (and sharpcap with polemaster camera)
chongo228
Posts: 136
Joined: Fri Nov 24, 2017 3:34 am

Re: Polar alignment isn't correct even though Sharpap Says excellent

Post by chongo228 »

backyardastrokiwi wrote:
Thu May 07, 2020 4:10 am

I've been using PA routine in Sharpcap for quite some time now and haven't had any issues until recently.

Any help would be much appreciated.
You could go back and try an older version that worked for you in the past and compare those readings to the newest SC version.
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admin
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Re: Polar alignment isn't correct even though Sharpap Says excellent

Post by admin »

Hi,

Atmospheric refraction will not account for an error that is that big – even at 30° latitude it's about two minutes of arc from memory. What will easily cause a problem like that though is something making the camera or guide scope move slightly as the telescope is rotated. Hanging USB cable that is putting weight on the back of the camera is quite enough to cause this effect (maybe not quite this magnitude though). Check out the polar alignment troubleshooting page here to see if any of the suggestions help

https://www.sharpcap.co.uk/sharpcap/fea ... leshooting

Cheers, Robin
backyardastrokiwi
Posts: 5
Joined: Sat Apr 18, 2020 12:55 am

Re: Polar alignment isn't correct even though Sharpap Says excellent

Post by backyardastrokiwi »

Thank you I will try these steps.
AussieHowie
Posts: 25
Joined: Fri Aug 11, 2017 12:23 am

Re: Polar alignment isn't correct even though Sharpap Says excellent

Post by AussieHowie »

Perhaps also check File>Settings>Polar Alignment tab where by default the lat and long used is set from your pc's timezone and stuff. If your pc clock etc has been changed by software update or something at that time has made the pc go nuts, then it could be incorrectly set from the pc. If you set by ascom using the mounts info or manually then the manual has info on this too and how it applies within that Settings tab for PA.

My workflow is to always manually enter the lat and long into that setting just to be sure it is correct.

BTW the online manual section is https://docs.sharpcap.co.uk/3.2/#General%20Tab
... scroll down to Polar Alignment settings.
jdaliix
Posts: 12
Joined: Mon Jun 11, 2018 2:01 am

Re: Polar alignment isn't correct even though Sharpap Says excellent

Post by jdaliix »

I also had this problem, but only recently. Last time out, in fact, when I've been using SC's polar alignment tool for three years. I had it at Excellent, literally as good as it can get. I use CPWI, and when I was finished with the alignment, CPWI told me the south and maybe east polar alignments were out by 40'. I would normally trust SC, but I think that CPWI thinking it was that far out was causing the tracking to be so poor the telescope was unusable that night. And there wasn't anything I could do to fix it, because I also don't have a great deal of luck with Celestron's All Star Polar Align utility through CPWI, and I don't want to have to undergo two full alignment and ASPA procedures.

I have 112.1 W 41 in Use This Location in the Settings, which is close enough, although I don't know enough about this to understand why it won't accept -112.1.

Anybody got any ideas? And thanks.

-- Jason
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