Plate Solving during Polar Alignment not successful

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Savari
Posts: 2
Joined: Sun Apr 14, 2019 2:13 pm

Plate Solving during Polar Alignment not successful

Post by Savari » Sun Apr 14, 2019 2:38 pm

SharpCap is finding enough stars but plate solving is in most cases not successful:

Camera: Lodestar
Guiding Scope: 60 * 240

I have checked the following preconditions:
- My telescope aimes near the pole. The deviation is within 5 degrees.
- The FOV seems ok.
- SharpCap finds more than 15 stars and displays them in yellow and red.
see https://drive.google.com/file/d/1jYkG-f ... sp=sharing

Nevertheless the plate solving is not successful.
I played with several settings, but the situation did not improve.
Astrometry.net can solve the picture.

See here an example Picture:
https://drive.google.com/file/d/1Pe1Ewv ... sp=sharing

In rare cases the solving is successful, but the time i consume for the polar alignment is far too long.
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Log_2019-04-12T21_19_36-6272.log
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Re: Plate Solving during Polar Alignment not successful

Post by admin » Sun Apr 14, 2019 8:36 pm

Hi,

I managed to get the image that you shared to solve for the polar alignment with the following settings

Noise reduction 0.5
minimum star with one pixel
maximum star with 24 pixels
black level threshold 1
Digital gain off

However the fact that such a specific set of settings is required may well mean that other frames would have trouble solving. There are a couple of things that make that particular image harder than average to solve. Firstly Polaris is very large in the image and without setting the maximum star width to 24, it doesn't get picked up as a star. Secondly there are a number of hot pixels which can be mistaken for stars. Usually the correct way to deal with hot pixels is to increase either the minimum star width or the noise reduction values, but in this case that reduces the number of stars being detected too far.

I would suggest trying adding 50% to or even doubling the exposure to get more lighting from the stars, which may allow you to then increase the noise reduction or minimum star width values to eliminate the hot pixels. Also set the maximum star width to 24 or more so that Polaris can be used as part of the plate solving procedure.

Hope this helps, Robin

Savari
Posts: 2
Joined: Sun Apr 14, 2019 2:13 pm

Re: Plate Solving during Polar Alignment not successful

Post by Savari » Mon Apr 15, 2019 4:05 am

Hi Robin,

Thank you for your quick response. I will try your suggestion on the next opportunity.

Best regards,
Dörte

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