[Aavso-photometry] Peranso vs Minima V2.3 question

[Wolfgang Renz]

I missed to insert the references of the original "Kwee-van Woerden"
papers:
1956BAN....12..327K - A method for computing accurately the epoch
of minimum of an eclipsing variable - Kwee, K. K.; van Woerden, H.
http://adsabs.harvard.edu/abs/1956BAN....12..327K

Clear skies
 Wolfgang

-- 
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV = WRe.vsnet = RWG.AAVSO



----- Original Message ----- 
From: "Wolfgang Renz" <w_renz at onlinehome.de>
To: "Yenal Ogmen" <yenalogmen at yahoo.com>
Cc: "AAVSO Photometry" <aavso-photometry at mira.aavso.org>
Sent: Saturday, February 14, 2009 10:46 PM
Subject: Re: [Aavso-photometry] Peranso vs Minima V2.3 question


Hi Yenal

You mean the "Minima" Software by Bob Nelson ?
http://members.shaw.ca/bob.nelson/software1.htm
http://members.shaw.ca/bob.nelson/Software/Minima25d.zip
the most current software version is V2.5d dated 2009-02-12.

Did you try it with the most current version too ?

If  you want detail, you must probably ask the authors directly.

> ~5 min is not a small difference right?

Right.

> Kwee-van Woerden

This method is basically an algorithm for processing equidistant data
of symetric LCs. So it applies for symetric EB LCs, but not for asymetric
ones including nearly all LCs of pulsators.

See e.g.:

1982IAPPP...7...14M - A FORTRAN Subroutine for Determining Times
of Minimum Light - Mallama, A. D.
http://adsabs.harvard.edu/abs/1982IAPPP...7...14M

Using slightly non-equidistant data might not have a very large
effect.

But if the LC is asymetric, the result will depend on the choosen
margins and the ToM will move more or less strongly depending
on the grade of the asymetry.
Its the same as with the trace-paper-flip method and the polynom
method that just includes even exponents.
But it shouldn't be an issue with the Pogson's half chord method
and the polynom method that also includes uneven exponents.

> Am I doing something wrong with Peranso?

Probably not.

Is your LC asymetric ?
Then this could explain the differences of the derived ToM with
Peranso.

If your LC is asymetric (and the minima stay fixed), Minima might
ignore the margin settings. To check this, feed the program with
different subsets of the data that contains just the data between the
wanted margins.

Clear skies
 Wolfgang

-- 
Wolfgang Renz, Karlsruhe, Germany
Rz.BAV = WRe.vsnet = RWG.AAVSO


 
> ----- Original Message ----- 
> From: "Yenal Ogmen"
> To: <Aavso-photometry at mira.aavso.org>
> Sent: Saturday, February 14, 2009 3:47 PM
> Subject: [Aavso-photometry] Peranso vs Minima V2.3 question
> 
> Hi all,
> 
> I just want to ask why I have different (~0.003 day=~5min) results of
> minima of the LC for the same file and the same left and right margins
> used both in MinimaV2.3 and Peranso?
> Both use the same algorithm: Kwee-van Woerden.
> ~5 min is not a small difference right?
> And I also observe that when you change the positions of the margins,
> Minima always give the same result but on the other hand Peranso's
> result changes when you change margins' position and this change is
> around 0.003 days. I am surpised with this as Minima is freeware and
> Peranso is not.
> Am I doing something wrong with Peranso?
> 
> Thank you in advance.
> 
> Yenal Ögmen
> Green Island Observatory (B34)
> www.greenislandobservatory.com
> Geçitkale
> North Cyprus