All Sky Plate Solver

Discussions on extending SharpCap using the built in Python scripting functionality
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oopfan
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All Sky Plate Solver

Post by oopfan » Fri Jul 14, 2017 4:31 pm

Hi Robin,

I downloaded All Sky Plate Solver and loaded the index files for my set up. I used it last weekend to get the orientation of my camera right (north up, east left). Is there any way that I can automate this with a script?

Sorry for all the posts. I guarantee that I will reach a level of knowledge and then it will all fall into place!

Thanks,
Brian

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Re: All Sky Plate Solver

Post by oopfan » Fri Jul 14, 2017 7:20 pm

I see that ASPS has a COM interface described here.
OK, it should be a simple matter to figure out how to call it.

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Re: All Sky Plate Solver

Post by oopfan » Fri Jul 14, 2017 7:31 pm

I am trying to understand why ASPS reports "Position Angle" (PosAngle) of 180 degrees when I am very certain that the image I give it is North:up and East:left. I crossed compared it to star charts, and even used ASPS's coordinate inspector feature by mouse-clicking around the image: declination increases going up, right ascension increases going left. Despite this, ASPS reports Position Angle of 180 degrees.

Their docs say:
"Reports the image rotation respect the celestial pole.
Clockwise rotation: 0° to 360°"

Not very clear or helpful. I tried emailing the developers a week ago. It appears as if no one is supporting the product anymore.

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Re: All Sky Plate Solver

Post by admin » Fri Jul 14, 2017 7:35 pm

I would be tempted to feed a few images to both a plate solver you can trust (ie nova.astrometry.net) and ASPS and see if you can see some correlation between the angles they give you to work out if there is a constant offset or a mirror or something.

cheers,

Robin

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Re: All Sky Plate Solver

Post by oopfan » Fri Jul 14, 2017 8:24 pm

Well, nova.astrometry.net's "Orientation" agreed with ASPS's "Position Angle". I am going to dig into astrometry.net's docs and get an explanation.

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Re: All Sky Plate Solver

Post by oopfan » Fri Jul 14, 2017 9:18 pm

astronomy.net says: "Up is -178 degrees E of N". It would make sense to me if it said "Down is -178 degrees E of N".
http://nova.astrometry.net/user_images/ ... #annotated

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Re: All Sky Plate Solver

Post by admin » Fri Jul 14, 2017 9:20 pm

Are fits files flipped vertically compared to PNG captures and the on-screen preview? I think they may be.

cheers,

Robin

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Re: All Sky Plate Solver

Post by oopfan » Sat Jul 15, 2017 1:11 pm

Robin,

I think you may be right. Welcome to the world of FITS! My educated guess is that a FITS file has embedded metadata whereas JPG does not, so astrometry.net makes the assumption that the JPG image is inverted due to the optics. That explains that but I am still perplexed as to why it just cannot take my JPG on face value and see that UP clearly points towards the North Celestial Pole! Then, in the wee hours of the morning, I thought to myself that this talk of "UP" is actually describing the sensor's reference frame. I think that is the answer.

If the weather cooperates ever again I will have to experiment with saving captures directly to FITS files, and then uploading to astrometry.net to see if any of this makes sense.

Thanks,
Brian

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