Troubleshooting Polar Alignment

Using SharpCap's Polar Alignment feature
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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

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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 585 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

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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?

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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

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