Re: [guide-user] Comets mag, how true?

Hello ;

I am an observer of comets and if you want my opinion on this topic you would say amvas options are good .
For one visual observers already if we legit devemos Magnitudes normally leaving the planetary ephemeris of any porgrama Guide9 , Starry , cartes du ciel etc etc ...
Now would also be a good reference tubieramos more accurate visual magnitudes of comets.
In the vast family of comets observer groups are given lists of comets observed both visually and CCD and not be a bad idea to have that list of comets in the Guide 9.0
One of the best groups of observers of comets is ;
http://es.groups.yahoo.com/group/Cometas_Obs
and on this website have observed comets posts lately with more reliable magnitudes ;
http://www.astrosurf.com/cometas-obs/
No difficulties to implement the GUIDE 9.0 a section to get the latest observations of most comets observed lately but would be helpful for comet watchers guide we use 9.0 for no groping and not be deceived by the ephemeris we get from the Minor Planet Center ( MPC ) that in most cases there are very real.

Greetings ;

J.Tapioles

Hola;

Soy observador de cometas y si quereis mi opinion sobre este tema vos diria que amvas opciones son buenas.
Por un lado los observadores visuales ya de por si no nos devemos de fiar de las Magnitudes que salen normalmente en las efemerides de cualquier porgrama planetario Guide9, Starry, cartes du ciel etc etc...
Ahora bien tambien seria bueno que tubieramos alguna referencia mas certera de las Magnitudes visuales de cometas.
En la amplia familia de grupos de observadores de cometas se dan las listas de los cometas observados tanto visualmente como CCD y no seria mala idea poder poseer esa lista de cometas en la guia 9.0
Uno de los mejores grupos de observadores de cometas es;
http://es.groups.yahoo.com/group/Cometas_Obs
y en esta web tienen puestos los cometas observados ultimamente con sus magnitudes mas fiables;
http://www.astrosurf.com/cometas-obs/
No se las dificultades para poder implantar en la GUIA 9.0 un apartado para tener las ultimas observaciones de la mayoria de los cometas ultimamente observados pero seria de gran ayuda para los observadores de cometas que usamos la guia 9.0 para no dar palos de ciego y no ser engañados por las efemerides que nos ponen desde el Minor Planet Center (MPC) que en la mayoria de ocasiones no son muy reales.

Saludos;

J.Tapioles

----- Original Message -----
From: Bill Gray
To: guide-user@yahoogroups.com
Sent: Monday, October 28, 2013 4:00 PM
Subject: Re: [guide-user] Comets mag, how true?

Hi Rolf, Gerhard,

>> So it would be a really big improvement if Guide could load this list
>> from the MPC and would have an additional setting for an "observed
>> magnitude limit".

It's an interesting idea... I don't think the MPC list will work very
well, though, because it relies on just the last magnitude observation.
If you look at the photometry reported to MPC, there are astonishing
variations from observer to observer. People use different filters and
apertures; some measure the nuclear magnitude, others the total magnitude.
(And _very_ annoyingly, the MPC format provides no clue as to what
filter was used for comet magnitudes. That is to say, you don't know if
the magnitude is a raw CCD magnitude or a visual one or, less rarely,
something else.)

My expectation would be that the sheer randomness of just using the
most recent observation would cause roughly as much trouble as the
current method, of computing a single absolute magnitude using all of
the photometry.

What we'd actually need would be a list of "current comet magnitudes"
that is based on, say, averaging the last few days or weeks of comet
photometry. (With, on occasion, some tweaking required because an
object is in outburst.) Better still would be if, instead of just
determining a "current magnitude", a "current _absolute_ magnitude"
was determined, i.e., one that takes the distance of the comet from
the earth and sun into account. But does anyone know of such a list?

-- Bill

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