Olympus-OM
[Top] [All Lists]

Re: [OM] IMG: celestial show (Eureka!)

Subject: Re: [OM] IMG: celestial show (Eureka!)
From: Ralf Loi <ralf_loi@xxxxxxxxxx>
Date: Tue, 23 Jun 2015 13:19:20 +0200
<<
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
-- 
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/

<Prev in Thread] Current Thread [Next in Thread>
Sponsored by Tako
Impressum | Datenschutz