Re: Tass-Landolt Comparison

["Thomas Droege" <tdroege2@earthlink.net>]

OK, I just looked at Mike's curve.  Very nice.  The error at fainter
magnitudes (Michael tells me) is due to the aperture photometry method.  

You might try averaging ove say .5 mag bins to see what the mean error is,
and then looking at sigma for each interval.  I found the mean error to be
quite small.  This means that if you take a lot of comparison stars then
all the errors tend to average out.  A good sign that Michael does things
withoug introducing a bias.  I found the mean error to be small but the
numbers are not where I can get at them since I planned on doing everything
over. 

You might also try Brian Skiff's big photometry file.

Tom Droege




> [Original Message]
> From: Michael Sallman <msallman@pro-ns.net>
> To: Tass <tass@listserv.wwa.com>
> Date: 2/26/2004 5:55:55 PM
> Subject: Re: Tass-Landolt Comparison
>
> If I had looked a little further in the email, I would have noticed
> Michael R.'s mention of Tech note 97.
> http://www.tass-survey.org/tass/technotes/tn0097.html
> In which he has information and plots of, wait for it....
> Landolt - TASS comparisons.
> Good thing mine look to be nearly identical to his.
> And we now have a few more stars.
>
> As they say, "Great Michaels think alike"
> :-)
>
> Mike
>
> Michael Sallman wrote:
> > I was cleaning out some of my old mail the other day, and I ran across a
> > thread from last November, where Tom and Michael R. had looked at MarkIV
> > data for 4 or 5 Landolt stars.
> > I decided to see what I could find in the database, now that Tom has
> > pretty much completed a full sweep of the northern sky.
> > I downloaded the Landolt list from
> > http://www.tass-survey.org/tass/catalogs/catalogs.html#landolt
> > and matched it to stars in the database. I came up
> > with 806 matches.
> >  From this list, I took a look at those that had at least 10 good
> > measurements in the database, and had V-R and R-I measurements in the
> > Landolt list. This reduced the number to 306 stars.
> > I have made some plots of the data (Landolt V vs. TASS V, etc.)
> > and put them on my website:
> > http://sallman.tass-survey.org/servlet/markiv/template/Landolt.vm
> > The g(x) lines are simple linear approximations of the data.
> > 
> > It looks like the TASS I values are almost always fainter than the 
> > Landolt I.
> > 
> > If anyone would like the data, just let me know.
> > 
> > Mike
> > 
> > P.S. I have finished loading the November and December data into the
> > database.
> > 
> > 
> > 
> > 
> > 
> > 
> > 
>
>
>