<<
It turns out that I had not burnt in the planets in the June 20
"triangle" formation, as I had thought. I did that for the June 21
picture, but not for the 20th. So why the heck was Jupiter coming out
almost as big and bright as Venus? I tried to get the planets
displaying their size and brightness with reasonable accuracy. It
wasn't easy. I had to turn off all sharpening, "clarity" (local
contrast), and believe it or not, noise reduction. Only then did the web
JPGs turn out as the image looked on the screen in Capture One. And then
I had to mask and re-sharpen the moon a bit.
Here's the result:
<http://gallery.leica-users.org/v/pklein/temp/P6200521+_7_+.jpg.html>
Here's the original processing:
<
https://www.flickr.com/photos/24844563@N04/18391108174/in/dateposted-public/
>
Lesson learned: Digital image editing is like quantum mechanics. When
things get small enough, really weird stuff starts to happen. :-)
>>
I checked the ephemerides for both planets. Jupiter has a magnitude of
-1.8 and Venus is -4.4. As a difference in one magnitude is a difference
in brightness of 2.512 times, the difference in brightness in these days
between the planets is roughly 11 times.
As for the apparent diameter, actually now Jupiter is slighlty bigger at
33" compared to the 28" of Venus, but the end result is roughly the same
because too little pixel have been involved. As an example with a 50mm
focal lenght:
Dia(mm) = Dia(arcsec) * focal / 206265 = 30 * 50 / 206265 = 0.007 mm = 7
micron (2 pixels on a E-M1)
I remember doing stars magnitude calculation from a CCD image some 25
years ago, but it was a sensor with big bit depth, and any pixel should
not be clipped.
Ralf
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