Bill,

Can you update and post that file so that the magnitudes displayed in
Guide8 are a little more realistic? Thanks,

John

--- In guide-user@yahoogroups.com, Bill J Gray <pluto@p...> wrote:
> Hi John,
>
> I think we have a likely culprit as to why the satellite
magnitudes
> might differ. Kevin Fetter kindly mentioned a page describing how
the
> absolute magnitudes of satellites are computed:
>
> http://www.satobs.org/brite.html
>
> which describes a difference in the magnitudes from the Molczan
and
> Quicksat files (see text below, copied from above URL). It looks
as
> if I should just knock the Quicksat magnitudes down (fainter) by
1.5.
>
> At least in theory, I could probably compute magnitudes based
on
> radar cross-section. The benefit of this would be that RCS data is
> available for almost all objects, whereas a lot of objects lack
either
> Molczan or Quicksat dat. The drawback would be that RCS correlates
> only loosely to physical size, which in turn correlates only
loosely
> to magnitude (that is, some satellites may be covered in black
paint
> and so forth.)
>
> -- Bill
>
> "...The "Molczan" magnitude values are based on 50%
illumination; the
> "Quicksat" values are based on 100% illumination. The difference
> mathematically is 0.8 magnitude. The "Molczan" magnitudes are 0.8
> magnitudes fainter due to this assumption.
>
> The "Molczan" values are based on "mean" magnitudes, while the
> "Quicksat" values are based on "maximum" magnitudes. Typically (for
a
> cylinder) the "mean" magnitude is about 0.7 magnitudes fainter than
the
> "maximum" magnitude. On average, the cylinder is tilted about 45
degrees
> relative to the observer compared to its maximum possible attitude.
>
> The sum of the two differences in magnitude is about 1.5
magnitudes.
> So a typical Cosmos rocket would appear in the Quicksat magnitude
> file as intrinsic 4.0 and in the Molczan file as intrinsic 5.5 ,
that
> is, its value of brightness in magnitude would be dimmer compared to
> the Quicksat value."