Polar align failure with ZWO mini scope

Using SharpCap's Polar Alignment feature
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stbkaiser
Posts: 152
Joined: Wed Aug 15, 2018 2:57 pm

Polar align failure with ZWO mini scope

#1

Post by stbkaiser »

Hi
I am trying to use the PA feature in sharpcap Pro v 4.0.7995.0 with my ZWO mini guide scope setup.
Zwo 30mm f/4 FL=120mm ,miniguide scope FOV=2.29 x 1.72deg,
ASI 120MM , 1280 x 960 pix, Sensor1/3"

I setup the CGX mount Level and within a few degs of NCP
When I run sharpcap and set it for AUTO Advance , it finds plenty of stars and gets past step 1
I rotate the mount (CGX) by hand 90deg.
Sharpcap now finds and highlights 45-60 stars and generates the concentric circles with stars highlighted
It shows the Center bullseye ring on the edge of the screen.
Now it displays SOLVING but it never completes the solve.

I have tried multiple times and it never solves.
If I run PA with my ASIAIR pro with the same camera-scope setup, it gives me a solution.

I can run Sharpcap with my 60mm F/4 guide scope , same camera and it Solves and gives me the calculated solution to Polar align.

According to your documentation , The ZWO mini guide scope should be able to give a solution for polar alignment.
"A field of view in the camera of between about 0.5 degrees and about 2.5 degrees. "
Per Astrometry.net analysis of the image from the ZWO mini guide scope FOV=2.29 x 1.72deg.

Do you think there is any way to fix this issue.
Thanks
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admin
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Re: Polar align failure with ZWO mini scope

#2

Post by admin »

Hi,

can you share a polar image captured using the ZWO mini scope? I know a lot of people use these scopes successfully, so there is nothing fundamental stopping it from working, perhaps just a need to adjust settings?

If you have not already, check out the troubleshooting guide - https://docs.sharpcap.co.uk/4.0/#Troubl ... 0Alignment

cheers,

Robin
stbkaiser
Posts: 152
Joined: Wed Aug 15, 2018 2:57 pm

Re: Polar align failure with ZWO mini scope

#3

Post by stbkaiser »

Hi Robin
Yes, I was planning on getting some snapshots at the zero and 90 deg positions for study.
After reading about PA on this forum, I also plan on starting the PA at 90 deg rotation to see if it will solve. I didn’t realize too many stars can cause a failure.
Nice to know others have used the ASI mini scope for PA with sharpcap.
I was worried it might have too small of FOV.

I left my mount setup from last night ( used ASIAIR PA); so if sharpcap has issues, it’s something with my settings.
I’ll let you know what happens.
Thanks for checking in with me.
Take care
Steve
stbkaiser
Posts: 152
Joined: Wed Aug 15, 2018 2:57 pm

Re: Polar align failure with ZWO mini scope

#4

Post by stbkaiser »

PA worked just fine this evening with the ASI ZWO mini scope setup.
I believe I had the gain set too high and it was finding too many stars.
I did run Sharpcap PA and tweaked the mount down to Excellent . (down in the 10-20" range on DEC & RA)
I then connected the ASIAIR Pro to the ZWO and ran it's PA routine.
It gave me a reading that the scope was out by more than 7' RA & 5' DEC
Now I'm worried about the accuracy of the ASIAIR .
I rely on it most of the time because where I usually setup my mount, My scope does not have a view within 5deg of the pole.
ASIAIR will give me a PA solution at that location.

I know there will always be differences between PA software but hoped it would be closer than this.
I guess as long as the PA solution gets the scope closer than a 0.5deg or so, the guide scope & PHD2 can handle the guiding.
Take care
Steve
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Re: Polar align failure with ZWO mini scope

#5

Post by admin »

Hi Steve,

I don't know about ASIAir, but the thing that SharpCap PA is most sensitive to in terms of errors is any sort of shift of the guide scope/camera relative to the RA axis as you rotate. Even a dangling USB cable can be enough to pull on the back of the camera and cause it to shift slightly as you rotate - there's more on this (and how to tell if it is happening) in the troubleshooting guide.

There was also a post on here a week or two back that linked to a page which would calculate how close your polar alignment needed to be based on various factors like sub length, etc. I just can't find that post again right now :(

cheers,

Robin
stbkaiser
Posts: 152
Joined: Wed Aug 15, 2018 2:57 pm

Re: Polar align failure with ZWO mini scope

#6

Post by stbkaiser »

Thanks for the suggestion on cable drag.
If the weather ever gives me a break, I will be a lot more conscience of how the guide cable is routed to ensure no deflections on the camera as I rotate.
It's easy for me to switch the camera between SC and ASIAIR without disturbing the camera setup.
For my own curiosity, I will do 3 -4 PAs , switching between Sharpcap and ASIAIR to see how repeatable they are and how they compare in readings.

As I explained , the locations where I can place my mount limit my options for Polar Alignment.
If I setup for a "Northern view", I have easy view of Polaris zone +/- 10 deg but not much else. So Sharpcap is Nice for PA
If I setup to give a view from S through W , I can' get within about9 deg of the pole. So I use the ASIAIR.
The joys of living with trees.

I will report back here on my findings.
Take care
Steve
zerolatitude
Posts: 156
Joined: Mon Mar 01, 2021 5:24 am

Re: Polar align failure with ZWO mini scope

#7

Post by zerolatitude »

admin wrote: Mon Jul 26, 2021 5:52 pm Hi Steve,

I don't know about ASIAir, but the thing that SharpCap PA is most sensitive to in terms of errors is any sort of shift of the guide scope/camera relative to the RA axis as you rotate. Even a dangling USB cable can be enough to pull on the back of the camera and cause it to shift slightly as you rotate - there's more on this (and how to tell if it is happening) in the troubleshooting guide.

There was also a post on here a week or two back that linked to a page which would calculate how close your polar alignment needed to be based on various factors like sub length, etc. I just can't find that post again right now :(

cheers,

Robin
This one? :-)

viewtopic.php?p=23403#p23403
zerolatitude
Posts: 156
Joined: Mon Mar 01, 2021 5:24 am

Re: Polar align failure with ZWO mini scope

#8

Post by zerolatitude »

stbkaiser wrote: Thu Aug 05, 2021 1:53 am As I explained , the locations where I can place my mount limit my options for Polar Alignment.
If I setup for a "Northern view", I have easy view of Polaris zone +/- 10 deg but not much else. So Sharpcap is Nice for PA
If I setup to give a view from S through W , I can' get within about9 deg of the pole. So I use the ASIAIR.
The joys of living with trees.
You can also polar align without a view of a CP.

1. Drift align with PHD2. Works, but longwinded
2. Use Norman's script for Sharpcap. Thread at viewtopic.php?f=14&t=2331
The first time setup is a little long, but explained in the thread. Once set up, its easy and quick without the need to see Polaris or SCP.
3. Nina nightly 1.11 build 119 (just out) has a new plugin for 3 point polar align. Its working is similar to 2, but the feedback mechanism is different.

If you are also guiding, the PA alignment accuracy required may not be as much as is commonly assumed. Link to calculator is in post above.
stbkaiser
Posts: 152
Joined: Wed Aug 15, 2018 2:57 pm

Re: Polar align failure with ZWO mini scope

#9

Post by stbkaiser »

Thanks for information.
I have done some drift alignment manually in the past.
Have not tried the PHD2 function yet.
Both ASIAIR pro and sharpcap polar alignment seem to work for what I need, and give fast results.
I have read from other discussions, that if a person is guiding, it may actually help to NOT be too accurate in the polar alignment so the guiding gives most commands in one direction.
But being an engineer, I always like to know if something ( hardware or software) is working properly ( accurately).
Take care
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