[Aavso-photometry] Transformation Coefficients

[Steven Orlando]

Mick,

An excellent software package Canopus:

http://www.minorplanetobserver.com/MPOSoftware/MPOCanopus.htm

Very reasonably priced.

Also, while there look for the link to Brian D. Warner's book on Lightcurve 
Photometry and Analysis. There are spreadsheet instructions in that book
----- Original Message ----- 
From: "Michael Crook" <m.j.crook at talk21.com>
To: "Tim Crawford" <tcarchcape at yahoo.com>; "aavso photometry" 
<aavso-photometry at aavso.org>
Sent: Tuesday, March 11, 2008 4:01 PM
Subject: Re: [Aavso-photometry] Transformation Coefficients


> Tim,
>
> I will be observing LPVs and I understand it is
> important to transform in these cases due to the
> colour differences between the red variables and the
> comparisons.
>
> Is there an 'idiots guide' available to transformed
> differential photometry? (I mean a REALLY basic
> guide?)
>
> Cheers,
>
> Mick
>
>
>
>
>
> --- Tim Crawford <tcarchcape at yahoo.com> wrote:
>
>> While we still have somewhat of a related thread
>> going
>> RE this specific topic (Michael Koppelman's last
>> post
>> on the topic: Differential vs. absolute magnitudes)
>> I
>> thought I would post some recent values showing the
>> difference between not transformed differential
>> photometry and transformed differential photometry
>> for
>> the benifit of those of you who have never ventured
>> into this territory.
>>
>> This was a recent observation of V371 Per in which I
>> had zero-pointed the instrumental magnitudes
>> (meaning
>> that the IM's would equal the sequence value) of the
>> main Comp star; because of this particular action it
>> makes it easy to look at this particular Spread
>> sheet
>> and pull off the following magnitude data.
>>
>> Filter - Not Transformed - Transformed - Difference
>>
>> V - 10.959 - 11.979 - .020
>>
>> B - 11.563 - 11.575 - .012
>>
>> R - 10.611 - 10.619 - .008
>>
>> I - 10.217 - 10.230 - .013
>>
>> It is important for you to understand  that other
>> systems (scope/ccd/conditions) could have
>> significantly larger differences or even
>> significantly
>> smaller differences (while pesumably the actual
>> transformed values would have been quite close) on
>> this same target, at the same time,  using the same
>> comp(s) stars, depending on the calculated
>> transformation coefficients for that system.
>>
>> Tim Crawford CTX'
>> Arch Cape Observatory
>>
>> http://homepage.mac.com/windwalker1/ACObserv.htm
>>
>>
>>
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>>
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>>
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>>
>
>
>
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