[Aavso-photometry] Software for combining time series data takenwith different filters to calculate transformed magnitudes

[Michael Newberry]

There are various ways to do what you want and some parts of it may be 
specific to the kind of project you are doing. I'm not sure I would mess 
with Excel, but that's my way of doing things. In my opinion, the best path 
would be to write a simple script, "customized" to your particular project's 
needs, that pulls the reduced photometry from a table (or tables) and 
interpolates it to a new time basis. In the end, I think a little light 
programming would be worthwhile to learn.

Michael Newberry

----- Original Message ----- 
From: "Lionel Catalan" <lcatalan at lakeheadu.ca>
To: "'Michael Newberry'" <mnewberry at mirametrics.com>
Sent: Friday, September 05, 2008 1:17 PM
Subject: RE: [Aavso-photometry] Software for combining time series data 
takenwith different filters to calculate transformed magnitudes


> Hi Michael,
>
> I'm studying high mass X-ray binaries, and the time scale of changes is
> greater than a few hours, whereas my images are taken every minute or 
> less.
> I would think that I could start by linear interpolation, since it would 
> be
> the simplest. My problem is that I am not a programmer, and I don't see 
> how
> I can easily implement an effective interpolation scheme in excel. I have
> hundreds of data points every night, and I obviously cannot manually
> interpolate between each couple of successive observations for each 
> filter.
>
> Lionel
>
>
> -----Original Message-----
> From: Michael Newberry [mailto:mnewberry at mirametrics.com]
> Sent: Friday, September 05, 2008 4:05 PM
> To: Lionel Catalan; aavso-photometry at mira.aavso.org
> Subject: Re: [Aavso-photometry] Software for combining time series data
> takenwith different filters to calculate transformed magnitudes
>
> Be careful about interpolation according to the kind of science you are
> trying to do. There's no patent answer for this.
>
> First of all, a general rule would be to interpolate only if the timescale
> of what you are studying does not vary significantly on the timescale of
> your observations. You want the data points to conincide with what is
> happening on the star. For example, if doing RR Lyr, UV Ceti flare stars
> asteroid rotation, etc., then I would use the actual observation times and
> not interpolated ones (but see item 2, below). OTOH, if you are doing Mira
> variables, etc., having a very slow rate of change, then I don't think
> anyone would care about interpolating near the time of observation.
>
> Second, what kind of interpolation would you use? Would you thread the
> points, do a piece-wide linear interpolation, cubic spline, etc.? Each 
> will
> give you a different magnitude value at whatever interpolated time you
> choose. Be sure you understand the effects of the method you use so that 
> you
> get numbers that are scientifically defendable.
>
> Michael Newberry
>
> ----- Original Message -----
> From: "Lionel Catalan" <lcatalan at lakeheadu.ca>
> To: <aavso-photometry at mira.aavso.org>
> Sent: Friday, September 05, 2008 12:49 PM
> Subject: [Aavso-photometry] Software for combining time series data
> takenwith different filters to calculate transformed magnitudes
>
>
>>I have times series data for B,V, and I filters that I would like to
>>combine  to calculate transformed magnitudes using transformation
>>equations. I use  a  filter wheel to change filters between images, so
>>I have sequences of  images  such as bvibvibvibvi etc.  Some images
>>have to be rejected from time to  time  due to wind or clouds, so the
>>sequences are not exactly regular. I already  have determined the
>>transformation coefficients for my system.
>> Essentially,
>> I think that I need a program (or perhaps an excel macro) that can
>>interpolate instrumental magnitudes for each filter to common times so
>>that  consistent values of b-v and v-i can be calculated.  I would
>>appreciate  any  suggestion.
>>
>> Lionel CTE
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>
>
>