Troubleshooting Polar Alignment

Using SharpCap's Polar Alignment feature
User avatar
admin
Site Admin
Posts: 3254
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Troubleshooting Polar Alignment

Post by admin » Tue Feb 21, 2017 10:23 pm

The most likely cause of problems with polar alignment is the plate solving failing due to not enough stars being detected. If you find this happening, here are some things you can try:

* Make sure you have decent focus - stars that are too blurry won't be picked up
* Turn up the exposure to 2-4s and possibly turn up the gain too
* Adjust the star detection controls on the first polar alignment screen.
* If you have problems with hot pixels being detected as stars, turn up the noise reduction or minimum star width
* If you are still having problems getting enough stars detected (you need 10-15 or more) turn up the digital gain.

If all of these fail to get plate solving working and you can see a decent selection of stars in the frame then please report a bug as follows:

* Save a frame in each of the two orientations of the RA axis that you have been using (save as PNG if possible - there should be no need for FITS)
* If you are getting plate solving results but they seem wrong, also save a screenshot showing each stage of the solving process.
* Post in this forum and include links to the images that you have saved and along with a description of the problem.

Saving frames of the polar field of view when you have a problem is the key to me being able to reproduce and hopefully fix any issues, so please don't forget!

cheers,

Robin

User avatar
admin
Site Admin
Posts: 3254
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: Troubleshooting Polar Alignment

Post by admin » Fri Mar 03, 2017 5:35 pm

Here is an example of a problem in polar alignment caused by too few stars. The image below was taken with a Lodestar X2 mono using 8s exposures by a SharpCap user on CloudyNights.
Field_1_Capture_0001.jpg
Field_1_Capture_0001.jpg (12.21 KiB) Viewed 6182 times
Although stars are visible in this image, they are too dim for SharpCap to spot them without making adjustments to the star detection settings. Note that if possible you should try to brighten the stars by adjusting the camera settings first (for example if you have a gain control for the camera, turn that up to inrease the brightness).

The above frame will not solve at all in SharpCap 2.9, but the star detection code has been improved in SharpCap 2.10 and that improvement along with some tweaks to the star detection settings is enough to make this frame solve correctly. In this case the critical settings for making the plate solving work are

Digital Gain : 2x
Noise Reduction : 1.0
Minimum Star Width : 1.0
(The black level threshold and maximum star widths are less important in this case).

It's worth knowing that you can test out the polar alignment plate solving yourself on an existing saved image file by following these steps:

* Select 'Test Camera 1 (Deep Sky)' from the cameras menu
* In the 'Testing Controls' group find the 'Image' control and press the Browse button (Properties button in 2.9)
* Select the saved image that you want to test.
* Once the image appears on the SharpCap display, activate Polar Alignment
* Now you can test out the polar alignment procedure on that image - you can even browse for and load a second image to move to step 2, as long as it has the same resolution as the first image.

cheers,

Robin

chris.cassford
Posts: 2
Joined: Thu Jun 15, 2017 4:00 pm

Re: Troubleshooting Polar Alignment

Post by chris.cassford » Thu Jun 15, 2017 4:21 pm

hi if this is an image using a loadstar and sharpcap how did they get Sharpcap to recognise the camera ?
i use a loadstar x2 and sharpcap wont recognise the camera?

User avatar
admin
Site Admin
Posts: 3254
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: Troubleshooting Polar Alignment

Post by admin » Thu Jun 15, 2017 8:05 pm

Right now you can only use Starlight Express cameras by installing the SX ASCOM driver and using that. However I expect to support SX cameras fully in the near future (next month or so).

cheers,

Robin

Surfer4329
Posts: 1
Joined: Mon Apr 29, 2019 1:10 am

Re: Troubleshooting Polar Alignment

Post by Surfer4329 » Mon Apr 29, 2019 1:25 am

I’m having trouble polar aligning with my zwo asi224mc mounted to my Orion 8” astrograph (800mm focal length). Sometimes it works fine and sometimes the software cannot plate solve as I’m aligning. In other words I can get the software to solve>click next>rotate RA axis>software solves (sometimes)>begin adjusting for polar alignment and software stops being able to solve. I’m wondering if my field of view is too small with this setup. However, i find that when I am able to successfully polar align with this setup my polar alignment is INCREDIBLY accurate. Maybe i need to up my exposure length to hit 15 or more stars in the field of view?

HeavyT
Posts: 3
Joined: Sun Nov 17, 2019 1:34 am

Re: Troubleshooting Polar Alignment

Post by HeavyT » Sun Nov 17, 2019 1:42 am

Hi all

Let me start by saying: I love Sharpcap

OK, so I have been using Sharpcap for polar alignment for about 4 months, absolute game changer. At home, I get aligned in about 90 seconds - rough in the mount orientation, get guidecam focused, PA routine, done.

Away from home I've encountered issues. I have successfully polar aligned with Sharpcap a couple of times away from home. Perhaps 2/3 of the time though I find it using 15 stars out of the 50 it registers, and still can't plate solve. Same exposure and gain and noise reduction settings.

I do update the location coordinates every time I'm in a new location.

I am currently attributing this to poor seeing, though I don't know why seeing that is good enough to register stars would not be good enough to plate solve?

Has anyone else encountered this problem?
Any advice would be much appreciated, thanks and clear skies👍

HeavyT

User avatar
admin
Site Admin
Posts: 3254
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: Troubleshooting Polar Alignment

Post by admin » Sun Nov 17, 2019 5:17 pm

Hi,

If you are using the same equipment – camera, guide scope etc. and the same camera settings and plenty of stars are being detected then one of the things to consider is whether your initial position is actually close enough to the pole when you are trying this when out and about. It's probably easier to get the initial position right in the familiar environment of your garden at home than it is in an unfamiliar environment.

One trick you can use to either confirm this is the problem or eliminate this is a problem is to save a couple of frames from the camera by using the snapshot button while you are trying to polar line and then later upload those to the plate solving website at http://nova.astrometry.net/upload to see what RA and declination you were pointing at when you were trying to run the polar alignment. If you have a local plate solving tool on your computer then you could use that instead of uploading to the website.

Hope this helps, Robin

HeavyT
Posts: 3
Joined: Sun Nov 17, 2019 1:34 am

Re: Troubleshooting Polar Alignment

Post by HeavyT » Mon Nov 18, 2019 9:53 pm

Thanks Robin, I'll definitely try the plate solving next time.
Spent hours on a couple of occasions trying different positions to better rough in the alignment and still just achieved lots of yellow boxed stars with no solving. I use an app to find stars & the pole and this usually works for me.

The other thing I wondered is whether Sharpcap might be trying to verify my product key online, but as I don't hotspot my phone to the laptop, it can't?

Once again, its a brilliant piece of software, thank you.

chongo228
Posts: 50
Joined: Fri Nov 24, 2017 3:34 am

Re: Troubleshooting Polar Alignment

Post by chongo228 » Mon Nov 18, 2019 11:56 pm

Does SC use the mini-histo stretch to plate solve?

Just curious because I can use 2-3 second exposures to plate solve but All sky plate solver needs 8 to 12 seconds to find enough stars. I've guessed SC is using the mini strecht I turn on and ASPS is using raw data.

I also think I read this someplace.....might help SC find stars if it's true.

User avatar
admin
Site Admin
Posts: 3254
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: Troubleshooting Polar Alignment

Post by admin » Tue Nov 19, 2019 8:16 pm

Hi,

No, SharpCap doesn't use the stretch functionality in the mini histogram for the star detection for plate solving, but there is an option to use digital gain in addition to the normal camera again if you need that. Normally I find a mono camera manages at 1 to 2 seconds exposure if you set the gain to a reasonably high level.

Also, the licence check for the licence key is completely off-line – there is no need for SharpCap to contact the Internet to check the key is valid.

Cheers, Robin

Post Reply

Who is online

Users browsing this forum: No registered users and 3 guests