Sunday, December 15, 2019

made 3D plots for analyses

Did some learning.

Trying to analyse my images, particularly those of double stars, to ensure they are not overexposed. Thanks to Steve, I have a good handle on the Expanded Histogram in Photoshop. I can easily know the number of pixels saturated.

I found similar information in Digital Photo Professional.

But I still wonder if I can't use Iris 5.59 for this. So I played around a bit... Figured out the Palette options in the Threshold dialog. Cool! Found the 3D function.

Both images are of the calibration star HD 148979 from my imaging run on 15 Jul '15. Exposures ranged from 15 seconds to 1.

3D visualisation of a double star overexposed

From IMG_5138.CR2 at 15 seconds. The right star, the bright one, is flat-topped, like a mesa. Overexposed. Over-saturated.

3D plot of double properly exposed

From IMG_5148.CR2 at 10 seconds. That's better. Rounded top. Properly exposed with little or no over-saturation.

So, clearly this is useful from an analysis point of view, while still requiring visual interpretation of the results. I can demonstrate that the second image is not overexposed. Happily, this is the one I chose at the time as the best. I guess I have a good eye.

I will continue searching for some sort of report function. I still want some hard numbers.... Maybe the aperture photometry feature in Iris will help.

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