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Incorrect magnitude of Mercury in Stellarium

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#1 skysurfer

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Posted 31 May 2020 - 09:37 AM

Using Stellarium I checked the magnitude of Mercury as we on Earth see it, which appears to be correct.

At its superior conjunction it is at its brightest, e.g. on the last one on May 5 it was -2.42 at 1.325 AU from Earth.

 

Now I 'move' to Venus, so as seen from Venus on the same date (May 5) from where it is also almost behind the Sun.

But then Stellarium shows -1.71 while being closer (1.028 AU from Venus) and the phase is also (almost) full: 98.8%.

This cannot be correct.

 

On the next superior conjunction (Aug 16) it is, as seen from Earth, about the same distance (1.348 AU), but quoted much fainter (2.02).

The phase is obviously the same, at any superior conjunction it is (almost) 100%.

 

This cannot be correct either.



#2 csa/montana

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Posted 31 May 2020 - 10:03 AM

Moved to Astro Software & Computers for better fit.


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#3 Alexander Wolf

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Posted 03 June 2020 - 02:21 PM

It's interesting for me: what value of magnitude for Mercury you are expected to see from the Venus?

 

Just for understanding: on Earth you are using (by default) model of planetary brightness, which published in Explanatory Supplement to Astronomical Almanac (2013), who based on real observations (light curve is defined by polynominal equation to fitting model to real data) and "generic model", who using on all Solar system bodies (except the Earth, but you may use it here too) and compute visual magnitude based on phase angle and albedo.

 

So, you compare model 1 and model 2 for planetary brightness and of course different models will give different data.


Edited by Alexander Wolf, 03 June 2020 - 02:23 PM.

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