Visual magnitude of Mercury is wrong

How exactly you are measured photometry of Mercury? Which algorithm of prediction of brightness for major planets of Solar system in Stellarium you used?

Okey let's try that on Thunderbird!

m = m_0 + 5*log_10 (r*Δ)

where:

r = distance sun to planet (in AE)

Δ = distance earth to planet (in AE)

m_0 = -0,42^mag + 3,8^mag *(i/100°)-2,73^mag *(i/100°)^2 + 2^mag *(i/100°)³

where:

i = phase angle

This is for Mercury.

I hope you can use it. If you use this you get +3,0 magnitudo on 1st of
january 2017 (0h UTC) instead of 3,85 mag. (Stellarium). As far as i
know this method is based on VSOP87.

Kind regards,

Christian Bucher

Am 17.12.2016 um 14:59 schrieb Alexander Wolf:
> How exactly you are measured photometry of Mercury? Which algorithm of
> prediction of brightness for major planets of Solar system in Stellarium
> you used?
>
> ** Changed in: stellarium
> Status: New => Incomplete
>

Where is source for this formula? Why you use i/100°?

Just for understanding - I see here mix of algorithms, provided by Pere Planesas (since + 3.8^mag) and D.L. Harris (Astronomical Almanac 1984 and later; this algorithm give V (instrumental) magnitudes) in first part.

These magnitude formulae have nothing to do with VSOP87.

I just saw we indeed have a sign error (+0.42) in the "Harris" (misnomer to be fixed in the near future) formula set. Thanks for reporting!

fixed in r8985

Hello Mr. Wolf

the book i took it from is called "Grundlagen der Ephemeridenrechung" by
Oliver Montenbruck. And he again used formulas based on the Astronomical
Almanac (DE405) and it's "Explenatory Supplement" (1992 edit.). I sent
you the formula as is. I didn't change anything on it! It works. I think
the author used "divided by 100°" because of the phase angle is in °
too. It's the phase angle just divided by 100. I now added a libreoffice
calc to show you what i mean.

Am 17.12.2016 um 17:11 schrieb Alexander Wolf:
> ** Changed in: stellarium
> Importance: Undecided => Low
>

Thank you very much! Your mail just collided with an answer mail to
Alexander Wolf. But it's great that I could help improving the software.

Am 17.12.2016 um 17:46 schrieb gzotti:
> These magnitude formulae have nothing to do with VSOP87.
>
> I just saw we indeed have a sign error (+0.42) in the "Harris" (misnomer
> to be fixed in the near future) formula set. Thanks for reporting!
>
> ** Changed in: stellarium
> Status: Incomplete => Confirmed
>
> ** Changed in: stellarium
> Assignee: (unassigned) => gzotti (georg-zotti)
>
> ** Changed in: stellarium
> Status: Confirmed => In Progress
>

Thanks for source of formulae.