Error was GSC 748-1618 period

[Tom Droege <tdroege2@earthlink.net>]

Michael worries why he can't match up the two curves more precisely.

To determine whether the miss-match is expected or not, we have to consider 
the errors.

I now know a little about the tass error.  At 11.5 the internal tass error 
is of order 0.05 mag for this data.  This is just the rms scatter of points 
taken in V and run through the pipeline.  We don't not know about the tass 
error when compared to standards.  I would be surprised if it were zero 
(with some error attached).

We need also to know something about the Koppelman error.  One can tell a 
little about the internal error by looking at the scatter of the measured 
points.  We know nothing about the Koppelman error when compared to 
standards?  I would again be surprised if it were zero (again with some 
error attached).

Just for tass the 0.05 mag number is just a "most of the time" number.  You 
can be unlucky and see 3 or even more times this error.

So thinking about the known errors, the match looks OK to me.  I would be 
more suspicious if it were closer to zero.

Tom Droege



At 12:44 PM 2/15/03 -0600, you wrote:
>Chris Lloyd and Paul Bartholdi were both kind enough to provide periods. 
>The difference between them was less than 5 seconds, so I split the 
>difference and used 0.7774. I gave different symbols to the TASS data, 
>which is about a year old, and my data, which begins right at the end of 
>December 2002 and into 2003. The new plot is here:
>
>http://www.lolife.com/astronomy/gsc748-1618/7481618_phase_3.jpg
>
>I want to go back and double-check the TASS data. Even if you dismiss the 
>the stuff at phase 0.1 as cloudy or something, it's impossible to make the 
>ascending and descending parts match up with my data. Even if you adjust 
>the zeropoint, there is something funny about the difference between the 
>two data sets.
>
> From the databases this appears to be a K-type star with B-R=1.4 
> (USNO-B1.0) and B-V=0.97 (Tycho-2) and probably a Cepheid of some sort.
>
>Michael Koppelman
>