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INDI Library v2.0.6 is Released (02 Feb 2024)

Bi-monthly release with minor bug fixes and improvements

FITS files and Plate Solving

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This past week I got serious about orienting my camera so that the image results in NCP:Up and East:Left. I snapped an image of Albireo and asked astrometry.net and All Sky Plate Solver for its opinion. You can see my image here .

Both astrometry.net and ASPS agreed with the orientation: "Up is -178 degrees E of N". I thought: what? I worked hard to ensure that North was Up. Why are you telling me that South is Up? I uploaded a JPG file not a FITS file, so my theory is that the plate solvers assumed that my telescope optics inverted the image. OK I can understand that.

Information is not easy to come by on the Internet about this topic, so I thought long and hard about it. Perhaps when the plate solvers refer to "UP" they are not referring to the top of the image -- instead they are referring to the top of the sensor. Does that make sense?

Also, FITS files contain metadata whereas JPG and PNG files do not. I am wondering if I should expect different results from the plate solvers if I capture my images in FITS files instead. I can certainly understand that getting the orientation of the sensor is important when applying darks, flats, and bias frames.

Would you recommend that I always capture to FITS?
6 years 8 months ago #17898

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Replied by Paul on topic FITS files and Plate Solving

I have also started testing plate solving recently and I believe INDI always sends a jpeg version.

Is it important to know what is referred to as up? To me that would depend on which way I was facing.

As they only have a jpeg to work with I would say it would be the top of the jpeg, as defined by the file.

Regards

Paul
6 years 8 months ago #17903

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Interesting. I captured an image to FITS. I submitted it to All Sky Plate Solver. It replied that Camera Angle was 2 degrees. Then I captured an image to PNG. But to view the PNG correctly I needed to rotate the image 180 degrees for North to be up. Interesting. This requires more experimentation. It may require a letter to be sent to NASA.
6 years 8 months ago #17909

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